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Page 1: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Permitting and Inspecting PV Systems

PV 403

Created and Written by: Kelly Provence

Page 2: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Permitting and Inspecting PV Systems

1

PV 403

Part 1

Permitting Solar PV Systems

Created and Written by: Kelly Provence

2

SOLAIRGENSchool of Solar technologyFounded in 2002

www.solairgen.com119 Highway 52 WestDahlonega, GA [email protected]

Kelly ProvenceIREC Certified Master Trainer

NABCEP Certified PV Installation ProfessionalNABCEP Certified PV Technical SalesLicensed Master Electrician

Page 3: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Table of Contents

Permitting Solar PV SystemsSolar energy, PV cells, modules and arrays 6PV array physical installation methods and concerns 17Residential PV system types and function 25

Interactive systems 29Micro-inverter and string inverter systems 33

PV systems with energy storage 44Example permit forms for residential 55

Commercial interactive PV inverters and systems 71Example permit forms for commercial 78

Labels, plaques and placement 83Important components of permitting PV systems 87

Inspecting Solar PV SystemsRoof access and physical installation parameters 92

Review and most common violations 105PV systems and the NEC 107

Significant changes from 2014 to 2017 editions 109PV system grounding 113

Review and most common violations 121Grounding electrode requirements 124

Review and most common violations 132

4

Voltage limits and calculations 134Conductor properties and selection 139Voltage drop calculations 152Overcurrent protection requirements 156

Review and most common violations 163Conductor protection 166

Review and most common violations 172Arc protection and first responder safety requirements 174

Review and most common violations 183Disconnect requirements 185

Review and most common violations 196Label and plaque requirements 199

Review and most common violations 209Interactive system utility connection 211

Review and most common violations 223Label and plaque example layout drawings 225

Addendum: Energy storage systems 229Requirements for all battery systems 231

Review and most common violations 237Energy storage systems operating over 60v 239

Review and most common violations 251Label and plaque example layout drawings 254

Page 4: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Key Terms

Photovoltaic (PV) also Solar Electric: The conversion of photon energy (light) into electron energy (electricity).

Inverter: A device that converts DC electrical energy to AC electrical energy.

Interactive inverter: An inverter that produces electricity in parallel with the utility electricity.

Stand alone inverter: An inverter that creates its own waveform and AC electricity from stored energy such as a battery.

Multimodal inverter: An inverter that can function as interactive or stand alone.

National Electrical Code NEC: A published advisory guide by the NFPA for safe electrical installations. It is placed into law by states and other jurisdictions.

The 2014 NEC is now in effect for most states in the U.S.

Authority Having Jurisdiction (AHJ): An organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, an installation, or a procedure.

Traveling at the speed of 186,000 miles per second (300,000 kilometers per second), radiation from the sun takes more than 8 minutes to reach Earth’s surface.

At any instant, Earth receives approximately 170 million Gigawatts of power from the sun.

The visible light is one portion of radiation that reaches earth. Ultraviolet, infrared and radio waves make up the other portions of non-visible light.

6

The Solar Source

Page 5: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Electron Movement and Speed

Upon striking the surface of the PV cell, photon energy is converted to electron energy.

• A fraction of a second later it is used by an electrical appliance.

• The conversion process (a band-gap magnetic field conversion) nets only about 16% to 21% of the photon energy into electron energy.

− 30% will be the maximum for this type of process.

Sunlight energizes electrons within the solar cell. Potential energy is created on the negative side of the cell.

When an electrical load is connected in between the negative and positive contacts, electrical energy is delivered to the load.

Mono-crystalline silicon ingots are grown in single crystal cylinders.

8

Over a period of hours, the molten silicon is grown to be a large cylindrical crystal up to 40″ in length and up to 8″ in diameter (5” and 6” for PV cells).• The ingot is a single uniform crystal. • The ingots are cut into wafers about 180μm thick.• The cells are doped to create a positive and negative side.

• An antireflective coating is applied.

• Electrical contacts are imbedded and soldered into the surface.

Page 6: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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PV ModulesCells are soldered to each other in series, negative to positive (front to back).• Voltage per cell is about .5 to .6 volts when operating.• Current per cell is dependent on its size (5” ≈ 6amps) (6” ≈ 8.5amps)

60 - 6” monocrystalline cells31.6v x 8.7a = 275w

72 - 5” monocrystalline cells37.8v x 6.1a = 230w

60 - 6” polycrystalline cells30.7v x 8.3a = 255w

STC (standard test condition) uses 1000W/m²at 25°C cell temp.

All systems are designed using STC data.

NOC (normal operating conditions) uses 800W/m² at NOCT at 20°C ambient temp.

(Cell temperature is 45° to 48°C)

Voltage and current are lower with NOC than STC. It is provided to give a more realistic operating condition when the module is installed

PV Module Test Conditions

10

Back to slide 152

Page 7: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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1000W/m² 25C

46C

The PV system is built from the module data tested at Standard Test Condition (STC).

Deviations in voltage are calculated for extreme temperatures using temperature coefficients (TC) provided for Voc and Pmax.

ModuleMax Power (Pmax) 300 wattsVolts (Vmp) 31.6 voltsCurrent (Imp) 9.57 ampsOpen Volt (Voc) 40.1 voltsSC Current (Isc) 10.23 amps

Typical residential interactive system – 1 sting of 13 in series (maximum)

SystemPmax 3,900 watts (3.9kW)Vmp 410.8 voltsImp 9.57 ampsVoc 521.3 voltsIsc 10.23 amps

12

x 13 = x 13 = x 1 =x 13 = x 1 =

Page 8: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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ModulePmax 300 wattsVmp 31.6 voltsImp 9.57 ampsVoc 40.1 voltsIsc 10.23 amps

System 1 stringPmax 2,400 watts (2.4 kW)Vmp 252.8 volts DCImp 9.57 ampsVoc 320.8 voltsIsc 10.23 amps

SolarEdge inverters with module level power electronics (MLPE), can control from 8 to 25 of their MLPE optimizers in a single string.

Typical residential interactive system – 1 sting of 8 in series (minimum)

x 8 = x 8 = x 1 =x 8 = x 1 =

14

ModulePmax 300 wattsVmp 31.6 voltsImp 9.57 ampsVoc 40.1 voltsIsc 10.23 amps

System 2 stringsPmax 4,800 watts (4.8 kW)Vmp 252.8 volts DCImp 19.14 ampsVoc 320.8 voltsIsc 20.46 amps

2 strings of 8 modules in series

x 16 = x 8 = x 2 =x 8 = x 2 =

Page 9: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Micro-inverters: The system voltage and amperage are AC.

15

InverterEach 250 watts

240 volts1 amps

SystemTotal 2kW AC 2.4kW DC

240 volts AC8 amps AC

ModulePmax 300 wattsVmp 31.6 voltsImp 9.57 ampsVoc 40.1 voltsIsc 10.23 amps

x 8 = x 1 =x 8 =

Low voltage system (battery based – 3 strings of 3 in series)

16

+

-

+-

+-

+-

+-

+-

+-

+-

+-

+-

Load

SystemPmax 2,700 watts (2.7kW)Vmp 94.8 volts Imp 28.71 amps Voc 120.3 voltsIsc 30.69 amps

ModulePmax 300 wattsVmp 31.6 voltsImp 9.57 ampsVoc 40.1 voltsIsc 10.23 amps

x 9 = x 3 = x 3 =x 3 = x 3 =

Page 10: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Steep Roof Mounts are typical for residential PV arrays.The modules are attached to rails that are attached to stand-offs that are bolted to the roof.

• This mounting method accounts for over 98% of residential rooftop installations.

17

18

Standing seam roofs can accommodate an alternate PV product that is directly attached to the metal roof.

• These thin-film PV modules have an adhesive for direct attachment.

• These account for a very small portion of roof mounted PV arrays (2003 to 2011).

− Less than 1% of residential rooftop installations

Page 11: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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PV roofing shingles are installed in place of standard shingles.

• The higher cost and specific training requirements has limited its success.

• These installations are seen in U.S. states with incentives and high electrical rates.

• CertainTeed and Dow currently have these products available in a few locations.

• These account for less than 1% of residential rooftop installations

− However Elon Musk says his products are the future of residential rooftop solar.

Product available in these states

20

Single pole mounts are a good where there is enough room.Optimum azimuth and array tilt can be attained.

• The array can be placed away from solar obstructions and the modules will operate at a lower temperature than roof mounted modules.

• Off grid systems should be pole mounted to optimize year-round performance.

− Close to 50% of rural residential PV systems are ground mounts.

− The figure is much lower in metropolitan areas.

Page 12: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Residential PV Array Pitched Roof Access

The modules are installed parallel to the roof so energy density is maximized.

• There should be roof access for other contractors and first responders.

• 3’ to the sides and top should be minimum for access.

The fire marshal is most concerned with these margins.

Access to the Roof

Dead Loads. The weight of materials of construction incorporated into the building, including but not limited to roofs, the weight of fixed service equipment, such as plumbing stacks and risers, electrical feeders, heating, ventilating and air-conditioning systems, and solar installations.

• Minimum dead load rating are 10 lb.ft²

− PV array directly attached parallel to roof add less than 4lb/ft²

− Standard roofing material including decking weighs less than 4lb/ft²

• The only time a standard residential roof top installation will be a weight problem is if there is already a problem with the dead load limit.

Environmental loads. Wind load, snow load, rain load, earthquake load, flood load. Wind loads are the primary concern for southern U.S. states.

• Racking manufacturers provide white paper on wind lift tests with their equipment for 90 mph and 120 mph.

• Most of Georgia is 90mph wind zone with the coast and northern mountains above 3000’ being the exception.

Physical Installation Concerns

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Page 13: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Lag screws are the most common type of fastener used to attach array mounting systems to wood structures, usually residential roofs.

• Calculate withdrawal strength

• Pre-drill hole 2/3 screw diameter

• Use butyl caulk and flashing

Attachment on Steep Sloped Roofs (greater than 3/12 pitch).

23

Composite shingle Bronzed for shake or composite

24

Direct Attachment

Butyl tape allows for the rail-less direct attachment.

• The butyl tape is placed below the attachment andSelf-seals when neoprene washer screws are usedto attach to the roof.

Roof Tech

Asphalt shingle roofs can be sealed with direct attachment

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In application there are three types of solar PV systems that we use.

1. Utility Interactive also known as Grid Tied or On-Grid

• The PV array DC energy is fed into the inverter that converts DC to AC. The energy is supplied to the AC loads and out to the grid.

• When the utility power is down so is the PV inverter output.

2. Stand Alone Off-Grid battery based

• The PV array charges the batteries and the inverter uses the stored battery energy to supply the premise’s loads.

− A back up generator is also required.

3. Bi-Modal or Multimodal battery based and grid interactive

• This system can operate in several different modes as the name suggests.

− Utility Interactive

− Net Zero or Self Consumption

− Stand Alone

Residential PV System Types and Function

26

PV System Safety Compliance Requirements

• DC Voltage is limited to 600v. PV voltage rises with cold temperatures so this must be calculated using ASHRAE minimum mean temperature.

− Micro-inverters control this; others require the installer to control it.

• Rapid shutdown for first responders. Rooftop PV arrays must reduce voltage 1’ outside the array boundary to 30v in 10 seconds when the rapid shutdown device is activated.

− Micro-inverters and SolarEdge control this; others require the installer to install it.

• Anti-islanding UL1741 listed inverters. The inverter must stop sending power into the grid during an outage.

− Included in all UL 1741 listed inverters

• GFDI equipped. The system must have ground fault detection on the PV array DC circuit that detects ground faults and shuts down equipment connected to the array if detected.

− Included in all interactive inverters; installer provides this with battery systems.

• AFCI equipped. The system must have arc-fault detection on the PV array DC circuit that detect arcs from the array and shuts down equipment connected to the array if detected.

− Included in all interactive inverters; installer provides this with battery systems.

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Example Layout Diagram Submitted with Permit ApplicationThis diagram provides the inspector with locations of all equipment.

Example Three Line DiagramThe flow of electrical current provide a simple way to see all components in the system and details of the conductus and conduit.

The line diagrams should show:

• Specifications of the PV equipment.

• The voltage and amperage of all circuits.

• Equipment conductor ratings

• The IEEE1547 and UL1741 compliance.28

• The location of disconnects

• Rating and location of overcurrent devices

• Capacity of service equipment

Page 16: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Utility Interactive Inverters

There are three main types of utility interactive inverters.

Micro inverters: These attach to each module and convert the single module DC energy to utility AC voltage (240v or 208v AC) (22v – 48v DC)

• One module per inverter.

• Some commercial micro-inverters allow 2 to 4 modules per inverter.

String inverters: A string inverter consists of a number of modules connected in series with 1 to 10 identical strings connected in parallel.

• Residential string inverters are usually 2kW to 10kW rated (1 – 4 strings)

− (240v AC) (150v – 600v DC)

String inverters with optimizers: Same as standard string inverter except each module has an optimizer connect directly to the module DC output.

• The optimizer is a DC to DC conversion device that improves performance and can reduce voltage to a safe level when AC power is disconnected at the inverter.

− (240v AC) (8v – 600v DC)

29

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Utility Interactive PV System

AC Power

Micro-inverterUsing micro-inverters

The flow of electrical energy is one-way up to the AC utility connection point

Page 17: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Utility Interactive PV SystemUsing string inverter

Rapid Shutdown device

Rapid Shutdown switch

DC Disconnect

32

Utility Interactive PV System

PV OptimizesString inverter with PV optimizers

DC Disconnect

Page 18: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Each module has its own inverter. The inverter is mounted on the rail underneath the module.

• Some PV modules have the inverter built into the module j-box (AC module)

• 15 to 21 of these inverters can be connected together before connecting to a back-feed AC breaker.

• AC output conductors are ran in PVC or metal conduit.

33

Micro Inverters

Inverter AC disconnect

Inverter AC power is disconnected when the inverter disconnect or main house power is turned off.

Module DC power is reduced to the single module power at the micro-inverter when the AC power is turned off.

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Micro-inverter Disconnect and Rapid shutdown

The Utility AC disconnect is also the main system AC disconnect and Rapid shutdown

The PV array AC disconnect serves three functions:

a) Servicing AC disconnectb) Utility AC disconnectc) Rapid shutdown system disconnect

3) PV array AC DisconnectUtility accessible

(AC)

4) Main house AC meter/disconnect

/ Rapid Shutdown

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Page 19: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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Single line diagram: Interactive system with micro-inverters

1. PV module dataPmax ____Voc ____Vmp ____Isc ____Imp ____

2. Inverter dataWatts ____Volts ____amps ____

SystemCircuit amps ____# of circuits ____

3. Conductor dataAWG ____Qty ____EGC ____

ConduitType ____Size ____

4. AC disconnectLabels

Volts ____Amps ____Rapid shutdown ____

5. Conductor dataAWG ____Qty ____EGC ____

ConduitType ____Size ____

6. Interconnection ratingsService ____aBusbar ____aMain OCD ____aInverter OCD ____a

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++ +

++ +

1234

kWH

J-box

PV array

AC Panel

Garage

Driveway

There is no DC potential. 1

PV systemAC disconnect 2

Rapid shutdown is provided via AC disconnect.

Layout diagram: Roof mounted array with micro-inverters

Red line is DC circuit

Blue line is AC circuit (interactive)

Meter

2

1

Page 20: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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The string inverter is usually located on the exterior wall of the house or it is located in the garage or basement.

• Most utilities require the AC disconnect to be on the exterior.

• The 2017 NEC requires the rapid shutdown device to be on the exterior

High DC voltage exists from the array to the inverter during operation.

• The DC voltage is usually between 150v and 500volts.

• The conductors must be in metal conduit if ran inside.

• The conduit must be marked “PV SOURCE CIRCUIT”

Residential String Inverters

Inverter AC disconnectRapid shutdown switch may be DC and/or AC.

2017 Rapid Shutdown device location

2014 device may be as far as 10’ away

38

String Inverters with PV Optimizers

Performance, safety and monitoring are enhanced with module level PV optimizers.

• The location of this inverter and AC disconnect is the same as the string inverter.

• The PV optimizer functions as the rapid shutdown device during a power outage or when the AC or DC switch is turned off.

High DC voltage exists from the array to the inverter during operation.

• The DC voltage is between 150v and 500volts.

• The conductors must be in metal conduit if ran inside.

• The conduit must be marked “PV SOURCE CIRCUIT”

Inverter AC disconnectRapid shutdown switch may be DC and/or AC.

Page 21: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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String Inverter Disconnect and Rapid Shutdown

With the SolarEdge systems, #2 is simple a j-box.

With a standard string inverter, #2 is the Rapid Shutdown device activated by #3 or #5.

Ground mounted PV arrays with the DC disconnect located at the array or the exterior of the home are not required to have a rapid shutdown system.

Main house AC meter/disconnect

/ Rapid Shutdown switch

35

63

Rapid Shutdown device

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Single line diagram: Interactive system with string inverters

1. PV module dataPmax ____Voc ____Vmp ____Isc ____Imp ____

4. InverterWatts ____Volts ____amps ____

SystemCircuit amps ____# of circuits ____

2. Conductor dataAWG ____Qty ____EGC ____

ConduitType ____Size ____

5. AC disconnectLabel

Volts ____Amps ____

Rapid shutdown ____

6. Conductor dataAWG ____Qty ____EGC ____

ConduitType ____Size ____

6. Interconnection ratingsService ____aBusbar ____aMain OCD ____aInverter OCD ____a

3. DC disconnectLabel

Max volts ____Max amps ____

Rapid shutdown ____

Page 22: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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++ +

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1234

kWH

J-box

PV array

Inverter

AC Panel

Garage

Driveway

DC disconnect 1

AC disconnect 2

Potential is the DC circuit from PV array to DC disconnect.

Rapid shutdown is at 1 and/or 2

Red line DC

Blue line AC

Layout diagram: Roof mounted array with string inverter

Red line is DC circuit

Blue line is AC circuit (interactive)

Meter

Potential high voltage DC crosses roof top of interior of structure.

1

2

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J-box

PV array

Inverter AC Panel

Garage

Driveway

PV array DC disconnect 1

The Inverter AC disconnect 2

Rapid shutdown is required at 2 or by separate listed device.

1234

kWH

Directional plaque for inverter AC disconnect

Red line is DC circuit

Blue line is AC circuit (interactive)

Meter

Potential high voltage DC crosses roof top of interior of structure.

1

2

Layout diagram: Roof mounted array with string inverter (remote disconnect)

Page 23: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

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++ +

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1234

kWH

PV array

Inverter

AC Panel

Garage

Driveway

DC disconnect 1

AC disconnect 2.

There is no DC potential inside the house.

Rapid shutdown is not required

Layout diagram: Ground mounted array

Red line is DC circuit

Blue line is AC circuit (interactive)

Meter

1

2

44

PV Systems with Energy Storage

Stand Alone and Multimodal: Both are designed to operate as Stand alone.

Stand alone systems can be a combination of DC and AC circuits or AC only.

Multimodal systems include AC circuits and can also operate in several other modes.

• Grid interactive (sells excess energy into the grid during high irradiance hours)

• Grid assisted stand alone (grid acts as a backup generator)

• Grid use mode (uses the grid to support loads during a specified time)

• Net Zero mode (meters usage so that minimal power is bought or sold to the grid)

Self Consumption: This is a single inverter interactive system with energy storage.

It is designed for a 24 hour period to prevent selling power into the utility grid.

i.e. “ The PowerWall”

• Some also operate in stand-alone mode for a short period of time.

• Multimodal inverters that operating in this mode refer to it as “Net Zero”.

Page 24: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Stand Alone or Bimodal PV System DC COUPLED

Input only

CRITICAL AC LOADS

Backup power sourcesOR UTILITY CONNECTION

45

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PV System with Energy Storage

DC coupled PV system with energy storage and inverter inside the structure.

Three disconnects are required to shut down all electrical components:

4) Shuts down the PV array5) Shuts down the critical backup AC loads6) Shuts down the DC energy from the battery bank

3) PV array DC or AC Disconnectand

(DC or AC)

4) Critical loads AC disconnect: inverter located inside

5) Plaque: Directory to all PV system and battery disconnects not located within site of the service meter.

6) Battery bank disconnect located inside the structure.

7) Main house AC meter/disconnect

/ Rapid Shutdown

73

45

6

Battery bank disconnect inside.

Page 25: Permitting and Inspecting PV Systems...2019/01/01  · Permitting Solar PV Systems Solar energy, PV cells, modules and arrays 6 PV array physical installation methods and concerns

Single line diagram: Multimodal PV system DC coupled

Since there are many more components with a battery system, it may be better to identify the products and circuits on this page with a subsequent page listing the details of the system.

• Arrows can be used to show the flow of energy during operation as well.

Stand Alone or Bimodal PV System AC COUPLED

OR UTILITY CONNECTION

Input only

CRITICAL AC LOADS

DC DISCONNECT

INTERACTIVE INVERTER

The battery inverter must control the interactive inverter’s power output when the batteries are fully charged. 48

PV power is fed through an interactive inverter into the critical loads AC panel.

AC DISTRUBUTION

CENTER

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PV System with Energy Storage

AC coupled PV system with energy storage and battery inverter inside the structure.

5) Shuts down the PV array6) Shuts down the critical backup AC loads7) Shuts down the DC energy from the battery bank

3) PV array DC or AC Disconnectand

(DC or AC)

4) Interactive inverter

5) Critical loads AC disconnect: inverter located inside

6) Plaque: Directory to all PV system and battery disconnects not located within site of the service meter.

7) Battery bank disconnect located inside the structure.

8) Main house AC meter/disconnect

/ Rapid Shutdown

83

56

7

Battery bank disconnect inside.

4

Single line diagram: Multimodal PV system AC coupled

NOTE: Three line diagrams are sometime required with residential systems even though they don’t usually provide any useful information.

Exception: Ground mounted PV arrays require a ground electrode system.

• This being the case a three line diagram would be helpful or at least a one diagram with grounding shown.

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1234

kWH

PV array

Garage

Driveway

Red line is DC circuit

Blue line is AC circuit (interactive)

Green line is AC circuit (stand-alone)

DC circuit disconnects 1

Interactive AC disconnect 2

Stand-alone AC disconnect 3

Layout diagram: Multimodal PV system with energy storage in basement

+ + + + + + + +

Batteries and Stand-alone inverter located in basement

Charge controller

DC Panel &OCDs

AC Panel &OCDs

Stand alone

Directional plaque for inverter AC disconnect

Interactive AC disconnect

Battery

inverter

Stand-aloneAC disconnect(only required to be readily accessible)

Preferred location for PV DC disconnect

2

3

1

1

3

Preferred location

Main

AC PanelAC Panel

Battery bank

Meter

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PV array

Garage

Driveway

Red line is DC circuit

Blue line is AC circuit (interactive)

Green line is AC circuit (stand-alone)

DC circuit disconnects 1

Interactive AC disconnect. 2

Stand-alone AC disconnect 3

Layout diagram: Multimodal PV system with energy storage in garage

++

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++

+

Stand alone

Directional plaque for Stand-alone inverter AC disconnect

23

1

Main

AC Panel

Battery

inverter

DC Panel &OCDs

AC Panel &OCDs

1234

kWH

AC PanelMeter1

Preferred location for PV DC disconnect

Potential high voltage DC crosses roof top of interior of structure.

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++ +

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PV array

Garage

Driveway

Red line is DC circuit

Blue line is AC circuit (interactive)

Green line is AC circuit (stand-alone)

PV array DC disconnect 1

Interactive AC disconnect 2

Stand-alone AC disconnect 3

Layout diagram: Multimodal PV system with energy storage in garage

++

++ +

++

+

Stand alone

Directional plaque for Stand-alone inverter AC disconnect

23

1

Main

AC Panel

Battery

inverter

DC Panel &OCDs

AC Panel &OCDs

1234

kWH

AC PanelMeter

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PV-Direct Stand alone and bimodal (Self-consumption)

A single inverter located inside or outside functions as AC coupled interactive and standalone inverter.

Critical Loads Main Loads

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Example Layout Diagram Submitted with Permit ApplicationThis diagram provides the inspector with locations of all equipment.

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Permit information pertaining to the Residential PV system

Select one in each category

Page 1a

Roof mount

Roof has adequate dead load rating for addition of PV array

Roof dead load rating is unverified

Roof attachment:

Flashed attachment

Direct attachment with butyl and polyurethane sealant

Other – specify _______________________________________________________

Railing and module attachment

Manufactured railing system with integrated grounding

Other – specify _______________________________________________________

First responder and service access

3’ access has been provided from roof ridge and one side of roof

Access is provided from a separate roof access direction and plane.

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Select one in each category

Page 1b

Ground mount

Grounding electrode system: ____________________________________________

Auxiliary electrode system

Bonded to premises electrode system

Grounding electrode conductor GEC) size ______AWG

Source conductor protection

Elevation _____FT above ground

Fence _____FT high _____FT away from array

Barrier – describe____________________________________________________

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Page 2a

Interactive – Micro-inverters ID name__________ rating kW_____ UL1741

Module name __________ watts _______ Qty _____

# of inverters ______ Inverter AC circuit rating ______a # of AC circuits ______

Inverter AC circuit output ______AWG OCD _____a EGC size _______AWG

PV system rating DC ______kW AC rating ______kW

Inverter AC output connection information:

Backfed breaker connection in AC load center

Ampacities: Busbar _____a Main OCD _____ Inverter OCD(s) _____a

Tap on load side of meter: Service feeders _____a Inverter OCD(s) _____a

Line side connection: Service feeders _____a Inverter OCD(s) _____a

AC disconnect label: Operating voltage ______v Operating current ______a

Rapid shutdown: AC disconnect N/A

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Layout Diagram with Labels (Interactive – Micro-inverters)

Location list1. Driveway at structure2. Service meter3. Main AC load center4. PV array w/micro-inverters5. Inverter AC disconnect/

Rapid shutdown switch + label6. Inverter interconnection point + label

Place numbers by associated equipment location

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Page 2b

Interactive – String inverter(s) ID name__________ rating kW_____ UL1741

Module name __________ watts_______ Qty ____ # in series _____

Max PV array DC voltage ______v e.g. Voc x (1+(((C-(+25C)) x TCVoc)

Controlled by inverter/PV optimizer

Max PV array DC current ______a e.g. Isc x 125% x # strings in parallel

PV output circuit to inverter ______AWG EGC size _______AWG

Inverter AC circuit output ______AWG OCD _____a EGC size _______AWG

# of inverter circuits _______ PV system rating DC ______kW AC ______kW

Inverter AC output connection information:

Backfed breaker connection in AC load center

Ampacities: Busbar _____a Main OCD _____ Inverter OCD(s) _____a

Tap on load side of meter: Service feeders _____a Inverter OCD(s) _____a

Line side connection: Service feeders _____a Inverter OCD(s) _____a

DC disconnect label: Max voltage ______v Max current ______a

AC disconnect label: Operating voltage ______v Operating current ______a

Rapid shutdown: AC disconnect DC disconnect Actuator N/A

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Layout Diagram with Labels (Interactive – String inverters)

Location list1. Driveway at structure2. Service meter3. Main AC load center4. PV array5. Rapid shutdown device6. PV array DC disconnect + label7. Interactive inverter

Place numbers by associated equipment location

8. Inverter AC disconnect/Rapid shutdown switch + label

9. Inverter interconnection point + label

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Page 2c

Stand Alone – DC coupled

Module name __________ watts _______ Qty _____

Max PV array DC voltage ______v e.g. Voc x (1+(((C-(+25C)) x TCVoc)

Controlled by PV optimizer

Max PV array DC current ______a e.g. Isc x 125% x # strings in parallel

PV output circuit to controller ______AWG EGC size _______AWG

Charge Controller (CC) rating kW _____________

Controller DC circuit output ______AWG OCD _____a EGC size _______AWG

Battery Inverter name __________ rating kW_________ Qty _____ UL1741

PV system rating DC ______kW AC rating ______kW

Battery type FLA, VRLA, Salt water, Li-ion, other ________________

Battery bank voltage ______v capacity________kWh Batter bank Isc ______

Battery bank disconnect label:

Nominal battery bank voltage ______ Max battery bank Isc _______

Arc clearing time for OCD ______ Date the calculation ______

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DC disconnect label:

Max voltage ______v Max current ______a Max CC current _____a

Rapid shutdown: DC disconnect Actuator N/A

Inverter AC output label: Operating voltage ______v Operating current ______a

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Layout Diagram with Labels (Stand-alone – DC coupled)

Location list1. Driveway at structure2. Service meter3. Main AC load center4. PV array5. Rapid shutdown device6. PV array DC disconnect + label7. Charge controller

Place numbers by associated equipment location

8. Battery bank with disconnect + label9. Battery inverter10. Inverter AC disconnect + label11. Directory to all electrical power sources

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Page 2d

Multi-modal – DC coupled

Module name __________ rating _______watts Qty _____

Max PV array DC voltage ______v e.g. Voc x (1+(((C-(+25C)) x TCVoc)

Controlled by PV optimizer

Max PV array DC current ______a e.g. Isc x 125% x # strings in parallel

PV output circuit to controller ______AWG EGC size _______AWG

Charge Controller (CC) rating kW _____________

Controller DC circuit output ______AWG OCD _____a EGC size _______AWG

Battery Inverter name __________ rating kW_________ Qty _____ UL1741

PV system rating DC ______kW AC rating ______kW

Battery type FLA, VRLA, Salt water, Li-ion, other ________________

Battery bank voltage ______v capacity________kWh Battery bank Isc ______

Battery bank disconnect label:

Nominal battery bank voltage ______ Max battery bank Isc _______

Arc clearing time for OCD ______ Date the calculation ______

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DC disconnect label:

Max voltage ______v Max current ______a Max CC current _____a

Rapid shutdown: DC disconnect Actuator N/A

Battery Inverter AC output ratings: (critical AC loads center)

AC disconnect label: Operating voltage ______v Operating current ______a

Battery Inverter AC input/output connection ratings: (interactive connection)

AC disconnect label: Operating voltage ______v Operating current ______a

Backfed breaker connection in AC load center

Ampacities: Busbar _____a Main OCD _____a Inverter Imax x 125% _____a

Tap on load side of meter: Service feeders _____a Inverter OCD(s) _____a

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Layout Diagram with Labels (Multimodal – DC coupled)

Location list1. Driveway at structure2. Service meter3. Main AC load center4. PV array5. Rapid shutdown device6. PV array DC disconnect + label7. Charge controller

Place numbers by associated equipment location

8. Battery bank with disconnect + label9. Battery inverter10. Inverter AC output disconnect + label11. Inverter AC input disconnect + label12. Inverter interconnection point + label13. Directory to all electrical power sources

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Page 2e

Multi-modal – AC coupled

Module name __________ rating _______watts Qty _____

Max PV array DC voltage ______v e.g. Voc x (1+(((C-(+25C)) x TCVoc)

Controlled by inverter/PV optimizer

Max PV array DC current ______a e.g. Isc x 125% x # strings in parallel

PV output circuit to inverter ______AWG EGC size _______AWG

Interactive inverter name__________ rating kW_____ Qty _____ UL1741

Battery Inverter name __________ rating kW_________ Qty _____ UL1741

PV system rating DC ______kW AC rating ______kW (battery inverter)

Battery type FLA, VRLA, Salt water, Li-ion, other ________________

Battery bank voltage ______v capacity________kWh Battery bank Isc ______

Battery bank disconnect label:

Nominal battery bank voltage ______ Max battery bank Isc _______

Arc clearing time for OCD ______ Date the calculation ______

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DC disconnect label:

Max voltage ______v Max current ______a

Rapid shutdown: DC disconnect Actuator N/A

Interactive inverter ratings: (feeding into the critical AC loads center)

AC disconnect label: Operating voltage ______v Operating current ______a

Battery Inverter AC output ratings: (critical AC loads center)

AC disconnect label: Operating voltage ______v Operating current ______a

Battery Inverter AC input/output connection ratings: (interactive connection)

AC disconnect label: Operating voltage ______v Operating current ______a

Backfed breaker connection in AC load center

Ampacities: Busbar _____a Main OCD _____a Inverter Imax x 125% _____a

Tap on load side of meter: Service feeders _____a Inverter OCD(s) _____a

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Layout Diagram with Labels (Multimodal – AC coupled)

Location list1. Driveway at structure2. Service meter3. Main AC load center4. PV array5. Rapid shutdown device6. PV array DC disconnect + label7. Interactive inverter

Place numbers by associated equipment location

8. Inverter AC disconnect + label9. Rapid shutdown switch + label10. Battery bank with disconnect + label11. Battery inverter12. Inverter AC output disconnect + label13. Inverter AC input disconnect + label14. Inverter interconnection point + label15. Directory to all electrical power sources

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Commercial Utility Interactive Inverters

Micro inverters: These attach to each module and convert the single module DC energy to utility AC voltage (208v or 480v AC) (16v – 60v DC)

• One to four modules per inverter.

String inverters: A string inverter consists of a number of modules connected in series with 1 to 10 identical strings connected in parallel.

• Commercial string inverters are usually 12kW to 50kW rated (4 – 10 strings)

− (208v, 277v or 480v AC) (200v – 1000v DC roof mounted)

Central inverters: A number of modules are connected in series with 20 to 300 strings connected in parallel depending on the size of the inverter.

• Central inverters consist of multiple combiner boxes feeding into a recombiner located at the inverter location.

− 480v Ac (200v – 1500v DC ground mounted)

Interactive with energy storage: Some residential models can be configured as 3-phase commercial. There are also a few large scale high voltage energy storage inverters.

− (208v – 480v AC) (60v – 600v DC)71

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Commercial Flat Roof and Low SlopedBallast is typically used on flat roofs (27 lb concrete cap blocks).

• The weight of the blocks keeps the array in place during high wind conditions. Ballast trays are connected to the module rack supports.

The roof must be rated to carry this excessive weight.

• This method accounts for the majority of flat roof installations.

Direct attachment is much less common because of higher installation cost.

• The array is usually 3’ to 4’ above the roof .

Direct attachment Ballasted

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Low Sloped Roof installations are direct mounted to the metal framing members

They are installed parallel to the roof in the same manner as residential, or on a slightly tilted A-frame design.

• These are typical for small to medium-sized manufacturing and service companies.

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Ground mounted commercial systems are usually multi-pole.The poles are usually pile driven or helical screwed into the ground.

• The poles are part of the grounding electrode system. If they are used as electrodes they must be bonded to the exiting electrode system.

• Ground mounted systems perform better than roof mounted systems because of cooler cell temperatures. They are also easier to service.

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Parking Canopies

PV modules provide a dual purpose function.

• The canopies provide sun protection for cars or outdoor seating areas.

• Modules operate cooler and more efficiently than roof mounts.

• Car canopies may also house battery charging stations for electric cars.

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Commercial Inverters and LocationsA rooftop PV system may use micro-inverters, string inverters or central inverters.

• The inverter AC and DC disconnects may be outside, inside, or on top of the building.

• The 2014 NEC requires Rapid shutdown within 10’ of the array; 1’ in 2017.

• Ground mounts may be 1500v and don notrequire rapid shutdown devices.

Central inverter String inverters

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Commercial Voltage ConsiderationsAC power from the inverter shuts down with loss of power.

DC power is still present from the array to the inverter

• Micro-inverter systems will maintain low voltage at the module location.

• String inverter systems vary depending on where the inverters are located.

− Roof located inverters contain high voltage very near the PV array.

• String inverters systems with optimizers can reduce DC voltage with power outage

• Central inverters were used on rooftop systems prior to 2013 but rarely after that.

Safe to work on DC and AC side with AC power off

Safe to work on the AC side with AC power off

Safe to work on DC and AC side with AC power off

Be aware of the potential inside DC conduit when AC power is off

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Permit information pertaining to the Commercial PV system

Check each that has been submitted

Page 1

Ground mount drawings submitted

Wind load data and calculations

Erosion control plan

Fence design and setback from PV array and equipment

Roof mount drawings submitted

Dead load and live load data and calculations

Wind load data and calculations

Grounding system submitted with electrical drawings

Module grounding method

Bonded railing components

Fire Marshal submitted data

Rapid shutdown method submitted with electrical drawings

PV array setback with access and egress shown

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Page 2 (do not fill in spaces on this sheet)

Module, PV array and inverter data shown on electrical drawings

• Module data: Module name___, Pmax___, Voc___, Vmp___, Isc___, Imp___

• Array data: Max Power___, Number of modules in array___

Modules/string___, Max voltage (coldest day)___

Strings/combiner___, Max current (Isc x 125%)___

Combiners/inverter___, Max current (Isc x 125%)___

Micro-inverter system data

• Inverter data: Inverter ID___, Power___, units/circuit___, circuit amps___, OCD___

• Output circuit Number of circuits___, Total # of inverters___

Volts___, Conductor type___, Conductor AWG___, EGC___

Conduit type___, size___ length___

String inverter system data

• Inverter data: Inverter name___, Rated power___, Volts___, current___

• Output circuit Conductor type___, Conductor AWG___, EGC___, OCD___

Conduit type___, size___ length___

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Page 2 continued (do not fill in spaces on this sheet)

Central inverter system data

• Combiner output: Current (Isc x # of string x 125%)___, Max volts (coldest day)___

Conductor type___, Conductor AWG___, EGC___

Conduit type___, size___ length___

• Inverter input: Current (Isc x # of strings x 125%)___, Max volts (coldest day)___

DC Overcurrent device___ (each)

• Inverter data: Inverter name___, Rated power___, Volts___, current___

• Output circuit Conductor type___, Conductor AWG___, EGC___. OCD___

Conduit type___, size___ length___

Grounding electrode system

Ground mounted: Electrode system and GEC shown on electrical drawings

Grounding electrode system data

Grounding electrode conductor data

Roof mounted: Equipment grounding conductor (EGC) bonded to AC grounding system.

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Roof LayoutCAD quality drawings are required for commercial PV systems.

• In this example the four separate string inverter arrays are identified by color (atypical).

• The location of disconnects, rapid shutdown and conduit should be shown

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The electrical riser diagram will be stamped by a Professional Engineer PE.

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Labels and Placement

On all PV array DC output conduits attached to or ran inside buildings

On all PV array output DC disconnects.

On the PV system disconnect: • AC disconnect for interactive systems• DC disconnect for DC coupled systems with

energy storage.

MAXIMUM CIRCUIT CURRENT

On all PV system inverter output AC disconnects.

On the switch that activates the rapid shutdown device.• AC disconnect for most interactive systems• DC disconnect or UL listed device on DC coupled

systems with energy storage.

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Labels and Placement

Within 3 feet of the service disconnect. This addresses PV output circuits outside the PV array 1 foot boundary.

The 2014 array boundary is 10 feet outside/5 feet inside.

• The placard must also denote the location of the rapid shutdown switch if it is not within sight of the service location.

Effective January 1st 2019

Within 3 feet of the service disconnect. This addresses PV output circuits outside the PV array 1 foot boundary.

It also addresses the voltage inside the array boundary.

• This is the part that will be effective on 1/1/2019

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Labels and Placement

Article 706.11

Installed at the service equipment location.

• The only guideline to this plaque or directory is that is comply with Article 110.21(B) for letter height and durability

• This may be a written directory or a drawing with writing as shown in this example.

Installed at a location acceptable to the authority having jurisdiction (AHJ).

• Off-grid stand-alone system. The plaque should be as you approach the structure from the driveway.

• Utility connect stand-alone system. The plaque should be at the service location.

X

PV arrayDC disconnect

PV systemAC disconnect X

Utility serviceAC disconnect X

MULTIPLE POWER SOURCES

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Labels and Placement

On equipment other than in dwelling units where the circuits can be accessed when energized.

• Most string inverters have dead front access panels to reduce this hazard.

• This usually occurs at AC switchgear.

Placed next to the inverter breaker back-feeding a branch circuit AC load center.

Placed on disconnects where the terminals are readily accessible and live when the disconnect is off and open.

• The bottom terminals are load side and usually de-energized when the disconnect is off.

− PV systems often backfeed circuits.

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Important components of permitting

Line diagram: Shows the flow of energy and makes it easier for the inspector to see what each part of the system is doing.

• Numerically referenced details on the line diagram. This provides a 1-2-3 process of installation verification for inspectors so that field calculations are unnecessary.

Layout diagram: Shows the location of all parts of the system, disconnects and directories.

List of labels: The label provides easy visual inspection.

• Contractors who provide accurate labels at all required locations are more likely to have a code compliant installation than those who don’t.

Cost of permit: It is important for a contractor to know the cost of permitting

Example: Base cost for residential interactive

Base cost for residential with energy storage

Adder: $/kW AC

Who can pull a permit: The State of Georgia requires a contractor to be licensed contractor.

• PV Systems fall under General contractor or electrical contractor.

• Electrical contractor must attach an affidavit if a general contractor pulls the permit.

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SOLAIRGENSchool of Solar technology

www.solairgen.com119 Highway 52 WestDahlonega, GA [email protected]

Question and Answer wrap up

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Permitting and Inspecting PV Systems

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PV 403

Part 2

Inspecting Solar Electric (PV) Systems

Created and Written by: Kelly Provence

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Key Code Issues with PV Systems

Physical installation:

• Access on the roof for first responders and service personnel

• Loading on the roof: Dead load limits and wind lift forces

• Attachments and penetrations affecting the roof integrity

Electrical installation (PV systems and the NEC)

• Improper grounding

• Poorly made connections or non-code compliant connector use

• Overvoltage on equipment or connectors

• Inadequate conductor size and protection

• Incorrect disconnect installation and placement

• Missing or inadequate labeling

• Non-compliant AC connection to service equipment.

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Residential PV Array Pitched Roof Access

The modules are installed parallel to the roof so energy density is maximized.

• There should be roof access for other contractors and first responders.

• 3’ to the sides and top should be minimum for access.

Most installations follow these guidelines but not all.

Access to the Roof

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Three foot minimum access is recommended

Modules are installed in tilted rows that provide 18” to 24” between each row. This is not service access.

• Aisle-ways should be minimum 4’, clearance to edge of roof should be minimum 6’

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Commercial PV Array Low Sloped Roof Access

Most installations provide more access than this guideline .

150’

150’

6’

6’ 4’

8’ walkway

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Dead Loads. The weight of materials of construction incorporated into the building, including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding and other similarly incorporated architectural and structural items, and the weight of fixed service equipment, such as cranes, plumbing stacks and risers, electrical feeders, heating, ventilating and air-conditioning systems, automatic sprinkler systems and solar installations.

• PV array directly attached parallel to roof; less than 4lb/ft²

Live Loads. Those loads produced (1) during maintenance by workers, equipment and materials; and (2) during the life of the structure by movable objects such as planters and by people.

Environmental loads. Wind load, snow load, rain load, earthquake load, flood load

Nominal Loads. The magnitudes of the loads (dead, live, soil, wind, snow, rain, flood and earthquake).

Physical Installation

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Dead Loads and Live Loads on Roofs

Residential roof dead load on the rafters are as following: Totals

• ½” Roof decking, plywood or OSB 1.5 lb.ft²

− Asphalt or wood shingle, metal sheet roofing 2 lb/ft² 3.5 lb/ft²

− Conventional clay/tile roofing 15 lb/ft² 16.5 lb/ft²

Commercial membrane roofs with metal decking and insulation 5 lb/ft²

Standard dead load ratings for residential and commercial roofs. 10 lb to 20 lb/ft²

• Consult the American wood council rafter span charts for details

• Consult the International Building Code (IBC )and the American Society of Civil Engineers (ASCE) 5-7 for snow and wind loads.

UNIFORM CONCENTRATED

Live loads for most flat and sloped building roofs. 20 lb/ft² 300 lb/ft²

Commercial roofs may have very little dead load margin for ballasted PV systems. A Structural or Professional Engineer (PE) will need to make the load assessment.

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Weight Loads and Wind Lift LoadsStatic loads are the weight of the PV array and ballasting to resist against wind lift.

Roof mounted PV arrays Total

• PV module weight 2.5 lb to 3 lb per ft². 3 lb/ft²

• Residential flush mounted racking .25 lb to .5 lb per ft². 3.5 lb/ft²

− Residential roofs are sufficient unless under built to begin with.

• Commercial flat roof racking without ballast 1 lb per ft². 4 lb/ft²

― Concrete blocks used for ballast weigh 27 lb

Flat roof mounted arrays occupy ≈ 28ft² per module

6 blocks x 27 lb = 162 lb ÷ 28ft² = 5.8 lb/ft² + 4 lb.ft² = 9.8 lb/ft²

Commercial roofs may require an engineer's calculation.

Ground mounts

― Pole mounted arrays will add about 4 lb to 5 lb per ft² without concrete.

― Poured concrete weighs around 100 lb to 130 lb per ft³.

― Penetrated ground resistance depend on soil type.

Ground Snow Loads for the Southeastern United States.

Taken from 2009 IBC

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• Wind speeds are based on a 3 second gust at 33 feet (10 meters) above ground.

90 (40)

ASCE 7-05; Chapter 6 Wind Loads

Wind exposure areas of the roof

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Structural Compliance:

Racking companies provide pre-engineered components and installation instructions.

• Require the contractor/installer to provide the racking design specifications (white paper).

Total of attachments for the PV array must equal the total wind lift lb/ft².

• Residential racking systems are pre-engineered for at least 90mph

• Commercial racking system will provide engineering data for each customer design.

Lag screws are the most common type of fastener used to attach array mounting systems to wood structures, usually residential roofs.

• Calculate withdrawal strength

• Pre-drill hole 2/3 screw diameter

• Use butyl caulk and flashing

Attachment on Steep Sloped Roofs

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PV arrays flashed mount standoffs and attachmentAll steep sloped roofs required an attachment and module mount system.

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Direct Attachment

Butyl tape allows for the rail-less direct attachment.

• The butyl tape is placed below the attachment andSelf-seals when neoprene washer screws are usedto attach to the roof.

Roof Tech

Asphalt shingle roofs can be sealed with direct attachment

Metal roofs are either corrugated or standing seam.1. The most secure attachment must be sealed by a

roofer

2. This is very secure if the bolt penetrates a rafter. It is less secure if it secures only to the lap seam.

3. This attachment is secured only to the metal roof but make no penetration and is leak-proof.

2. Attached to the corrugated lap seam 3. Attached to the standing seam104

1. Attached structural rafters

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Residential:

1. Bolting and flashing to the roof are the two areas where installers make mistakes with the physical installation.

• Selecting the wrong grade of lag bolt. (residential systems use stainless steel)

• Galvanic corrosion: Stainless steel and tinned copper are used to prevent corrosion.

• Improper torqueing of the bolts

• Missing the rafter with the lag bolt or splitting the rafter.

• Direct attachment without flashing: The potential to improperly install sealant.

2. Insufficient setback from vent pipes and other roof structures.

Most common violations

Addressing these potential violations:

1. Since these are almost impossible to see these areas with roof mounts, it may be beneficial to have the contractor list the materials and methods of attachment (on the permit).

2. It is easy to see setbacks from the ground.

− Cut off vent pipes may be difficult to see without a high powered flashlight or a visit into the attic to see if there are vent pipes located where the PV array is located.

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Commercial:

1. Improper installation of ballasted array have the greatest potential for roof damage.

• Exceeding the roof structure dead load rating.

• Failure to distribute the ballast as the roofing manufacture has specified for wind lift.

• Failure to protect the roof membrane from sharp edges of metal or plastic racking.

• Setting ballast treys directly on top of roofing rock ballast (membrane scaring).

2. Insufficient setbacks and clearances for walkways

Most common violations

Addressing these potential violations:

1. Require an engineer's letter of dead and live load for the roof.

− Require a copy of the engineered layout for the PV array and ballast load distribution.

− Require the contractor to show the method of membrane protection on the permit.

− It will be obvious if the PV array is sitting on the roof ballast or membrane.

2. It will be easy to see if necessary setbacks have be observed for other equipment.

− 48” minimum from electrical equipment, 42” minimum from metallic structures

− 48” minimum for walkways

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PV Systems and the NEC

Many changes to solar PV articles in the 2017 NEC are clarifications. These should be implemented immediately.

Some other changes are already in place as a common practice but will not become law until Georgia adopts the 2017 version.

The text is taken directly from the 2014 and 2017 NEC with minor rephrasing. − Rephrasing in this course is not to be considered official substitution for NEC text.

2017 NEC additions or changes are highlighted blue or with a blue bar to the left.

2014 NEC text deleted from 2017 NEC are highlighted in purple.

Comments are usually indicated by the use of this symbol: before the comment, e.g.

Author’s comments

Authorities having jurisdiction (AHJs) usually adopt the latest NEC version one year after it’s official date. Persons engaging in electrical work should possess three NEC versions; previous, current and upcoming when made available.

108

PV System Safety Compliance Requirements

• Residential DC Voltage is limited to 600v. PV voltage rises with cold temperatures so this must be calculated using ASHRAE minimum mean temperature.

• Commercial DC Voltage is limited to 1000v. PV voltage rises with cold temperatures so this must be calculated using ASHRAE minimum mean temperature.

• Rapid shutdown for first responders. Rooftop PV arrays must reduce voltage 1’ outside the array boundary to 30v in 10 seconds when the rapid shutdown device is activated.

− Micro-inverters and SolarEdge control this; others require the installer to install it.

• Anti-islanding UL1741 listed inverters. The inverter must stop sending power into the grid during an outage.

− Included in all UL 1741 listed inverters

• GFDI equipped. The system must have ground fault detection on the PV array DC circuit that detects ground faults and shuts down equipment connected to the array if detected.

− Included in all interactive inverters; installer provides this with battery systems.

• AFCI equipped. The system must have arc-fault detection on the PV array DC circuit that detect arcs from the array and shuts down equipment connected to the array if detected.

− Included in all interactive inverters; installer provides this with battery systems.

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Significant changes from 2014 to 2017 NEC

• 1500vdc is allowed with ground mounted PV arrays. New

• Articles referencing voltage above 1000v have further replaced the previous references to above 600v. New

• Rapid shutdown requirements have been expanded and clarified; the boundary is now restricted to one foot of the PV array. New and redefined

• Fusing both + and – is no longer required with ungrounded systems so long as there is a disconnect that opens both conductors simultaneously. New clarification

• PV wire requirement for ungrounded systems is rewritten to allow USE-2 if AC side has a grounded neutral. New clarification

• Grounded PV array conductors do not require the white marking if GFDI is the bonding point to the ground (functionally grounded). New clarification

• Grounding electrode conductor requirements are simplified. Reduced and clarified

• Article 691 Large Scale PV Systems was added for systems sized 5MW and larger. New

• Article 706 Energy Storage Systems and Article 710 Stand-Alone Systems were added and Articles were moved from Article 690. Moved, clarified and expanded

110

Accessible (as applied to wiring methods): Capable of being removed or exposed without damaging the building structure or finish or not permanently closed in by the structure or finish of the building.

Accessible, Readily (Readily Accessible): Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is required to use tools (other than keys), to climb over or remove obstacles or to resort to portable ladders, and so forth.

Functional Grounded PV System. A PV system that has an electrical reference to ground that is not solidly grounded.

This is a new term for defining grounded PV arrays with a GFDI device.

− The 1a to 4a GFDI fuse does not provide a solidly grounded conductor

− A solidly grounded PV system would not have a GFDI fuse or a GFDI device.

− In the U.S. most AC services are solidly grounded at the main AC disconnect. It is extremely rare for a PV system to be solidly grounded.

Voltage, Nominal: A value assigned to a circuit or system for the purpose of conveniently designating its voltage class (e.g., 120/240 volts, 480Y/277 volts, 600 volts).

Informational Note # 3: Battery units rated at nominal 48 volts DC may have a charging voltage up to 58 volts. In DC applications, 60 volts is used to cover the entire range of float voltages.

Important NEC Terms

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111

Alternating-Current (AC) Module: A complete, environmentally protected unit consisting of solar cells, optics, inverter, and other components, exclusive of tracker, designed to generate AC power when exposed to sunlight.

Charge Controller: Equipment that controls DC voltage or DC current, or both, used to charge a battery.

Diversion Charge Controller: Equipment that regulates the charging process of a battery by diverting power from energy storage to direct-current or alternating-current loads or to an interconnected utility service.

DC to DC Converter: A device installed in the PV source or output circuit that can provide an output DC voltage and current at a higher or lower value than the input DC voltage or current. (MPPT devices) (PV Optimizers)

DC-to-DC Converter Output Circuit. Circuit conductors between the dc-to-dc converter source circuit(s) and the inverter or dc utilization equipment.

DC-to-DC Converter Source Circuit. Circuits between dc-to-dc converters and from dc-to-dc converters to the common connection point(s) of the dc system.

Other NEC Terms for PV Systems

112

Generating Capacity. The sum of parallel-connected inverter maximum continuous output power at 40°C in kilowatts.

Hybrid System: A system comprised of multiple power sources. These power sources may include photovoltaic, wind, micro-hydro generators, engine-driven generators, etc...

Interactive System: A solar PV system that operates in parallel with and may deliver power to an electrical production and distribution network. For this definition an energy storage subsystem of a solar PV system, is not another electrical production source.

Multimodal (formerly Bimodal): Equipment having the capabilities of both utility-interactive inverter and stand-alone inverter.

Stand-Alone System: A solar photovoltaic system that supplies power independently of an electrical production and distribution network.

Battery storage systems are typical with stand-alone, however a solar well pump that operates without battery storage is also a stand alone system.

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PV System Grounding690.41 System Grounding.

(A) PV System Grounding Configurations. One or more of the following system grounding configurations shall be employed:

(1) 2-wire PV arrays with one functional grounded conductor

GFDI fuse connecting the grounding conductor and a current conductor.

(2) Bipolar PV arrays according to 690.7(C) with a functional center ground reference.

(3) PV arrays not isolated from the grounded inverter output circuit

(4) Ungrounded PV arrays

The reference to article 690.35 was removed along with 690.35. Both (3) and (4) regard the AC side grounded conductor to be adequate.

(5) Solidly grounded PV arrays as permitted in 690.41(B)Exception

See next slide for Exception.

(6) PV systems that use other methods that accomplish equivalent system protection in accordance with 250.4(A) with equipment listed and identified for the use.

At least 99.9% of the systems installed in the U.S. will fall under (1) or (4)• Most are ungrounded PV arrays.

114

690.41 System Grounding.

This 2017 NEC article below was moved from 690.5 of 2014.

(B) Ground-Fault Protection. DC PV arrays shall be provided with dc ground-fault protection meeting the requirements of 690.41(B)(1) and (2) to reduce fire hazards.

Exception: PV arrays with not more than two PV source circuits and with all PV system dc circuits not on or in buildings shall be permitted without ground-fault protection where solidly grounded.

(1) Ground-Fault Detection. The ground fault protective device or system shall detect ground fault(s) in the PV array DC conductors and components or any functional grounded conductors; it must be listed for providing PV ground-fault protection.

(2) Isolating Faulted Circuits. The faulted circuits shall be isolated by one of the following methods:

(1) The current-carrying conductors of the faulted circuit shall be automatically disconnected.

(2) The inverter or charge controller fed by the faulted circuit shall automatically cease to supply power to output circuits and isolate the PV system dc circuits from the ground reference in a functional grounded system.

Both grounded and ungrounded systems are included in the article. The special requirements for ungrounded systems has be removed because it was illogical.

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Residential grounded systems: Fuses are .5 to 1 amp Commercial grounded systems: Fuses are 2 to 5 amp Ungrounded systems: Shut down at .3 amps

115

Location of GFDI

Interactive systems:

Grounded inverters have a fuse built into the inverter. It is protected but accessible by screw attachment.

Ungrounded inverters use an internal high impedance reference connection (+ to G) and (- to G).

Battery based systems: Grounded

Charge controllers may have a fuse built into it. If so, it is protected but accessible by screw attachment.

DC load centers are a common location for this device. The breaker will be in tandem with one or two PV array inputs.

G

-

+ +

+ +

690.43 Equipment Grounding. Exposed non–current-carrying metal parts of module frames, equipment, and conductor enclosures shall be grounded in accordance with Art. 250.134 or 250.136(A) regardless of voltage.

(A) PV Module Mounting Systems and Devices. Devices and systems used for mounting PV modules and for bonding module frames shall be listed, labeled, and identified for bonding PV modules. Devices that mount adjacent PV modules shall be permitted to bond them.

(B) Equipment Secured to Grounded Metal Supports. Devices listed, labeled, and identified for bonding and grounding the metal parts of PV systems shall be permitted to bond the equipment to grounded metal supports. Grounding shall be contiguous from rail to rail section by use of a listed bonding jumper.

(C) With Circuit Conductors. Equipment grounding conductors shall be ran with array conductors within and beyond the array.

Module frames and metal racking provide grounding within the array boundary.

Equipment grounding and bonding requirements

116

Rail to rail Rail to grounding conductor Module to rail

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117

Bonds to module

Bonds to rail Bonds to rail

Bonds to module

End clamp Mid clamp

Tinned coper bonding lug#14 - #4 CU

Integrated bonding is now standard with most raking systems

#6 copper provides EGC bond to all rails

Size of Equipment Grounding Conductors

690.45 Size of Equipment Grounding Conductors. Equipment grounding conductors for PV source and PV output circuits shall be sized in accordance with 250.122.

Where no overcurrent protective device is used in the circuit, an assumed overcurrent device rated in accordance with 690.9(B) shall be used.

e.g. PV max circuit current = Isc x 125% x 125% = OCD

118

• Increases in equipment grounding conductor size to address voltage drop considerations shall not be required.

• The equipment grounding conductors shall be no smaller than 14 AWG.

690.46 Array Equipment Grounding Conductors

The article states that EGC smaller than #6 shall comply with 250.120(C)

• Where installed in a raceway, PV array EGCs and GECs not larger than #6 AWG shall be permitted to be solid.

250.120 (C) Equipment grounding conductors smaller than 6 AWG shall be protected from physical damage.

The smallest equipment grounding conductor not ran in a conduit is #6 cu.

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Table 250.122 Size of Equipment Grounding Conductors (EGC)

119

Size all grounding conductors using the chart below.

Always use copper conductors for exterior applications.

250.98 Bonding Loosely Jointed Metal Raceways. Expansion fittings and telescoping sections of metal raceways shall be made electrically continuous by bonding jumpers.

Bonding Requirements

120

Railing is commonly jointed to other sections for larger PV array rows.

• Newer bond rated splices are now being provided by the racking companies.

• If the splice is not bond rated, a bonding jumper must be installed.

Expansion joint bond

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A functionally grounded system is not solidly grounded. The functional ground is either a GFDI fuse or low amperage or a high impedance electrical reference.

Solidly grounded PV systems only occur on small ground mounted arrays with two or less strings and no DC components connected to a building.

AC electrical systems are almost always solidly grounded with the neutral and grounding conductor boned at the service disconnect location.

Ground fault detection is required on all PV array source and output circuit conductus that are not solidly grounded.

Exposed non-current carrying metallic part of PV system and other electrical equipment must be grounded and connected to the premises grounding system.

Equipment grounding conductors are sized in Table 250.122. The assumed OCD used in the table is calculated from the continuous current x 125%.

When current carrying conductors are oversized to compensate for voltage drop, equipment conductors are not required to be size up proportionally.

Equipment grounding conductors smaller than #6 must be protected from physical damage.

Insulated grounding conductors must be colored solid green or green and yellow. Conductors sized #4 and larger may be marked with green tape at their point of access.

PV array bonding devices must be listed for the environment and use.121

Review: Equipment Grounding Requirements

Conduits used a grounding path must be bonded together with listed conduit connectors.

Bonding jumpers are required where metal parts of normally grounded systems are not solidly bonded.

The 2017 NEC removes the requirement to mark a functionally grounded PV source or output conductor white. Only solidly grounded conductors are to be marked white.

AC side neutral conductors are to be marked white or light grey.

122

Review: Equipment Grounding Requirements, cont.

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123

Most common violations

1. Exposed PV array EGC is sized smaller than #6.

2. Bonding connectors are not properly torqued.

3. Bonding lugs between rails are not listed for the use and environment.

4. DC coupled battery based systems fail to install a GFDI device.

Addressing these potential violations.

1. Ground mounts are easy to see. Roof mounts are not easy to see; ask for verification on exposed EGC during the inspection (#6 minimum).

2. PV modules, racking systems and inverters all provide instructions on torque spec. Ask for a sheet on torque specs and ask how it was verified.

3. I have seen aluminum grounding lugs used on PV arrays . They should be tinned copper or stainless steel. Ask for verification on the grounding lugs.

− Micro-inverters use integrated bonding so issues in #1 and #3 are addressed by the manufacture. Violating the installation procedures would violate the warranty.

4. Look for the GFDI device in either the charge controller or the DC panel.

690.47 Grounding Electrode System.

(A) Buildings or Structures Supporting a PV Array. A building or structure supporting a PV array shall have a grounding electrode system installed in accordance with Part III of Article 250.

This is the same requirement for AC grounding electrodes outlined on subsequent slides.

PV array equipment grounding conductors shall be connected to the grounding electrode system of the building or structure supporting the PV array in accordance with Part VII of Article 250.

Part VII 250.130(A) For Grounded Systems. The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor.

This refers to the AC grounded system. In the U.S. the gross majority of AC electrical system are grounded.

This connection will usually be made by bonding the DC equipment grounding conductor to the AC equipment grounding at the inverter.

124

Grounding Electrode System Requirements for PV Systems

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(A) Continued. For PV systems that are not solidly grounded, the equipment grounding conductor for the output of the PV system, connected to associated distribution equipment, shall be permitted to be the connection to ground for ground-fault protection and equipment grounding of the PV array.

In other words, the bond between the PV array equipment ground may be bonded to the inverter AC equipment bond. This is the necessary bond to the AC grounding electrode system.

For solidly grounded PV systems, as permitted in 690.41(A) (5), the grounded conductor shall be connected to a grounding electrode system by means of a grounding electrode conductor sized in accordance with 250.166.

These are the small isolated PV arrays with not more than two PV source circuits not on or in buildings.

Review the requirement for 250.166 on subsequent slides

Informational Note: Most PV systems installed in the past decade are actually functional grounded systems rather than solidly grounded systems as defined in this Code. For functional grounded PV systems with an interactive inverter output, the ac equipment grounding conductor is connected to associated grounded ac distribution equipment. This connection is often the connection to ground for ground-fault protection and equipment grounding of the PV array.

125

Grounding Electrode System Requirements for PV Systems

The bond is in the inverter and/or the location of GFDI.

126

690.47(B ) Additional Auxiliary Electrodes for Array Grounding.

Grounding electrodes shall be permitted to be installed in accordance with 250.52 and 250.54 at the location of ground and roof-mounted PV arrays.

• The electrodes are permitted to be connected directly to the array frame(s) or structure.

• The grounding electrode conductor shall be sized according to 250.66.

• The structure of a ground-mounted PV array shall be permitted to be considered a grounding electrode if it meets the requirements of 250.52.

• Roof mounted PV arrays shall be permitted to use the metal frame of a building or structure if the requirements of 250.52(A)(2) are met.

Auxiliary grounding electrodes by definition are not bonded to the existing grounding electrode system and are not required to comply with 25Ω to ground.

This electrode should either be bonded to the existing electrode system or it should have a resistance to ground of 25Ω or less, otherwise it should not be installed.

NOTE: The primary reason for an auxiliary grounding electrode is to protect against lighting strikes. Failure to tie it into the existing electrode system will increase exposure to ground lighting dispersal effects.

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Roof Mounted PV Array

Functionally grounded Systems with GFDI:

The array equipment grounding conductor is bonded to the inverter AC EGC.

127Bonding point EGC and GEC

Roof mounted PV array

Roof Mounted PV Array

Functionally grounded Systems with GFDI:

The auxiliary grounding electrode (if used) should be bonded to the premises GEC.

Only for lightning prone areas

128Axillary GEC bonded to EGC and premises GEC

Roof mounted PV array

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Ground Mounted PV Array

Functionally grounded Systems with GFDI:

The GEC from the PV array to the premises grounding electrode system must be no smaller than the existing GEC.

129

Ground mounted PV array

Frame of the PV array connected to existing electrode system

Ground Mounted PV Array

Functionally grounded Systems with GFDI:

The PV array grounding electrode must be installed according to 250 Part III.

130

Ground mounted PV array

Frame of the PV array must meet grounding electrode requirements

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250.52 Grounding Electrodes; specifies the approved methods and materials to effectively ground AC and DC systems.

(A) Electrodes Permitted for Grounding.

(1) Metal underground water pipes (10 feet underground)

(2) Metal In-ground Support Structure(s) with or without concrete (10 feet vertically contacting the earth).

• If multiple of these support structures are present at a building or a structure, it shall be permissible to bond only one into the grounding electrode system.

(3) Concrete encased electrode (20’ #4 cu or corrosion resistant ½ inch metal bar)

(4) Grounding ring (20 feet of #2 AWG cu 30 inches below surface of earth)

(5) Rod electrode (8 feet in length 5/8’ diameter 30 inches below SOE)

(6) Other listed electrodes

(7) Plate electrodes (2 ft² surface ¼ inch diameter and 30 inches below SOE)

(8) Other local metal underground structures

Approved Grounding Electrodes

131

Grounding electrode systems must provide a low resistance to earth ground. The NEC specifies 25 ohms or less as the minimum standard.

• The system owner or engineer may specify a lower resistance.

A DC grounding electrode system is required for buildings or structures supporting a PV array.

• Where an AC system is installed on the structure with a grounding electrode system, this will be the grounding electrode system for the PV array.

• Where a PV array is installed on the ground, a grounding electrode system must be installed in accordance with Article 250 Part III.

• Additional auxiliary grounding electrodes for array grounding are permitted to be installed at or as close to the PV array location as possible. They must meet the standard for grounding electrodes set forth in article 250.52.

− If installed, they should be bonded to the existing grounding electrode system.

DC Grounding electrode conductors are only required where a PV array is ground mounted or an auxiliary grounding electrode system has been installed.

• DC grounding electrode conductors are required to connect system grounding conductors with the grounding electrode systems.

AC Grounding electrode conductors are required at the first point of disconnect where equipment grounding conductors and solidly grounded conductors are bonded.

• On the AC side this is at the service disconnect.132

Review: Grounding Electrode Requirements

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133

Most common violationsGround mounted systems:

1. Inadequate DC grounding electrode system.

2. Failure to protect the grounding electrode conductor

Addressing these potential violations.

1. Inadequate DC grounding electrode system for ground mounted systems

• A separate auxiliary ground in electrode system should be connected to the existing AC grounding electrode system with a bonding conductor sized to the larger of the two.

• If the existing grounding electrode system is further than 100’ from the PV array, the DC grounding electrode system must meet Article 250.52 requirements.

2. Failure to protect the grounding electrode conductor.

• A #6 copper GEC requires no additional protection as long as it is attached to a building or the electrical equipment structure.

− A #4 is required when the GEC is ran to the grounding electrode system away from protection unless it is in conduit or ran underground. e.g. 18”

Voltage Limits and Calculations

Art. 690.7 Maximum Voltage The maximum voltage of PV system dc circuits shall be the highest voltage between any two circuit conductors or any conductor and ground.

• PV system dc circuits on or in one- and two-family dwellings shall be permitted to have a maximum voltage of 600 volts or less.

• PV system dc circuits on or in other types of buildings shall be permitted to have a maximum voltage of 1000 volts or less.

• Where not located on or in buildings, listed dc PV equipment, rated at a maximum voltage of 1500 volts or less, shall not be required to comply with Parts II and III of Article 490.

Art. 490 Part II Equipment (Switchgear and Industrial Control Assemblies) covers overcurrent device ratings and locations.

Art. 490 Part III EQPT. (Specific Provisions) covers disconnect locations and ratings.

Table 490.24 provides minimum clearances for live parts.

134

The 1500v provision is for commercial ground mounted PV arrays. All equipment used for installation and testing must be rated 1500v.

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Art. 690.7(A) Photovoltaic Source and Output Circuits Use one of the following.

(1) Use the PV module manufactures Standard Test Conditions STC temperature coefficients (TCVoc) and module Voc. Calculate the coldest day voltage from the module data and number of modules in series.

e.g. Voc x (1+(TCVoc x temperature difference from STC))

(2) Multiply Table 690.7 temperature correction factor times the module STC Voc and number of modules in series. (for c-Si modules without temperature coefficients)

(3) PV systems of 100kW or larger may use an alternate industry standard method calculated by a licensed professional electrical engineer.

This includes 5MW plus PV systems noted in 691.6 and 691.8.

Art. 690.7(B) DC-to-DC Converter Source and Output Circuits

(1) Single DC-to-DC Converter. The max voltage for output circuits of the dc-to-dc converter shall be the maximum rated voltage output of the dc-to-dc converter.

(2) Series Connected DC-to-DC Converters. Go by manufactures instructions.

• If not stated in the instructions the max voltage shall be the sum of the max ratings of the DC-to-DC converters connected in series

135

Voltage Calculations

The NEC suggests using the ASHRAE table for a minimum temperatures source.

Residential interactive string inverters usually have a 600v max, 12 to 14 in series.

Micro-inverters often have a max voltage of 48v, 1 module per inverter

e.g. Module data sheet STC Voc of 36v and TCVoc of .35%/°CAtlanta ASHRAE minimum temperature is -12°C 37°C lower than STC 25°C

36v x (1+(37°C x .0035)) = 40.662v max voltage for the module(1.1295) use 1.13 as a generic standard for Atlanta

14 module in series x 40.662v = 569v max system voltage

Temperature difference between the extreme annual min. temp and STC 25°C

136

(A)(1) Method Example

Excerpt from ASHRAE table

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(B)(1) and (2) Example

137

500

350

59.3-60-60.5

15

60

48

8 - 48

The inverter and DC to DC converter limit string voltage to 500v

DC-to-DC converter

138

Review: Voltage Limits and Requirements

Residential voltage max is 600v

Commercial rooftop voltage max is 1000v

Commercial ground mount voltage max is 1500v

Max PV array voltage = Voc x (1+(coldest day temp. difference from STC x TCVoc))

• PV inverter/optimizer controlled max voltage is provided by the manufacturer.

Maximum DC-DC (optimizer) voltage is listed on the device or system

Voltage violations with interactive PV systems are almost unheard of because design programs are readily available from inverter manufacturers.

• The inverter and other electronic equipment also monitor voltage.

Most common violations

Addressing this potential violation.

Rule-of-thumb formula for Atlanta, GA: Find the PV module Voc and use the following.

Voc x number of modules in series x 1.13 = Max voltage on coldest day

NOTE: SolarEdge controls voltage; this should be shown on the permit.

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Conductor Properties and selection

139

• USE-2 or PV wire is used for PV array source conductors.

• THWN-2 or XHHW-2 is used in conduit ran outside and/or underground

• THHN is used in conduit ran indoors

140

Conditions of Use

310.10 Uses Permitted: Conductors are exposed to several climatic conditions and they must be rated for these conditions.

• Some of these are dry, moist, wet, direct burial, low and high temperatures, UV light exposure, hard use, corrosive material and proximity to other conductors or equipment.

• The conductors must be rated or listed for the specific condition of use.

(A)Dry locations: all conductors listed in the NEC are rated for dry locations

(B) Dry and Damp locations: The following types are rated for damp locations. FEP, FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW.

(C) Wet locations: MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THWN, THWN-2, XHHW, XHHW-2, or ZW or be listed for use in wet locations

Conductors ran in conduit underground are in a Wet Location.

It is best to check the conductor manufactures listing for specifics. Many conductors have multiple listings for type and use.

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Conductor Bending Radius

Each conductor has a maximum bending radius depending on the type, specs and voltage.

• The radius is given in # times the diameter of the conductor.

e.g. Chapter 9 Table 5 provides diameters for several cable types.

#10 RHW-2 = .236” diameter x radius factor of 8 = 1.89” bending radius

1.89 x 3.16 = 5.93”

USE-2 is allowed a maximum radiusof 5x the diameter in Art. 338.24.

e.g. 5 x .236 = 1.18”

About the radius of a coffee cup

141

< 1.89” > < 1.89” > 5.93”

Determine Circuit Continuous Rating

142

690.8 (A) Calculation of Maximum Circuit Current.

(1) PV source Circuit Current

(1) The sum of parallel-connected PV module–rated short circuit currents (Isc) x 125%.

# of modules connected in series x Isc x 125% = max continuous current

(2) For PV systems with a generating capacity of 100 kW or greater, a documented and stamped PV system design, using an industry standard method and provided by a licensed professional electrical engineer, shall be permitted.

• The current value shall be based on the highest 3-hour current average resulting from the simulated local irradiance on the PV array accounting for elevation and orientation.

• The current value used by this method shall not be less than 70 percent of the value calculated using 690.8(A)(1)(1).

The National Solar Irradiation Database can be used with the program behind PVWATTS to determine 3-hour irradiation measurements for various tilts and azimuths at a great number of locations.

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143

690.8 (A) Calculation of Maximum Circuit Current.

(2) Photovoltaic Output Circuit Currents. The maximum current shall be the sum of parallel source circuit maximum currents as calculated in 690.8(A)(1).

(3) Inverter Output Circuit Current. The listed maximum current shall be the inverter continuous output current rating.

(5) DC to DC Converter Output Current. The maximum current shall be the dc- to-dc converter continuous output rating..

690.8 (B) Conductor Ampacity. PV system currents shall be considered to be continuous.

Circuit conductors shall be sized to carry not less than the larger of 690.8(B)(1) or (2).

Or where protected by a listed adjustable electronic overcurrent protective device in accordance 690.9(B)(3), not less than its current rating.

(1) One hundred and twenty-five percent (125%) of the maximum currents calculated in 690.8(A) before the application of adjustment and correction factors.

e.g. Circuit continuous current x 125% = required conductor ampacity.

Determine Circuit Ampacity Requirements

Art. 110.14 Electrical Connections(C) Temperature Limitations; The temperature rating associated with the ampacity of a

conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device.

Equipment is sometimes rated lower than the selected conductor.

Equipment Lug Temperature Limitations

144

Some residential DC equipment

Some AC equipment

Most commercial DC equipment

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145

310.15 Ampacity of conductors rated 0 – 2000 volts:

(1) Tables: Ampacities for conductors shall be permitted to be determined by tables as provided in 310.15(B)

(2) Selection of Ampacity. Where more than one ampacity applies for a given circuit length, the lowest value shall be used.

Exception: If the lower ampacity section of the conductor length is less than 10 feet and less than 10% of the total length, the higher ampacity may be used.

If more than 10 feet or 10% of the conductor is exposed to a higher temperature than the rest of the conductor length, the entire conductor length must be derated to that higher temperature.

(3) Temperature Limitation of Conductors. The temperature rating of the full conductor circuit length may not be exceeded during its continuous operation.

e.g. A conductor rated 75C (167F) may not use in a location that will experience a temperature of 76C (168F).

• That applies to the equipment as well.

Ampacity Rating of Conductors

PV source circuit conductor open air ampacity ratings

American Wire Gauge

146

Table 310.15(B)(17) Allowable Ampacities of Single-Insulated Conductors Rated Up to and Including 2000 Volts in Free Air, Based on Ambient Temperature of 30°C (86°F)*

PV modules typically have #12 PV wire (USE-2) rated 35a to 40a.

Field installed cables are all #10 PV Wire (USE-2) rated 50a to 55a

Derating these conductors is not necessary since source circuits require less than 15a

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Conductor Ampacities in Conduit

Select minimum current rating based on temperature rating of equipment

PV output conductors and all other conductors ran in conduit.

Table 310.15 (B)(16) gives amperages for up to 3 conductors in a raceway at 30°C.

147

or

Article 690.31(A) Wiring Systems.

For ambient temperatures exceeding 30°C (86°F), conductor ampacities shall be corrected in accordance with Table 690.31(A).

148

This table is for PV source and output conductors only.

For all other conductors use the table referenced on the next slide.NOTE: The two tables correction factors are the same on identical temperatures.

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Table 310.15 (B)(2)(a) Ambient temperature correction factors based on 30°C (86°F)

Table 310.15(B)(3)(c) Conduits exposed to sunlight or on rooftops

Raceways shall be installed 7/8” above the roof.• If installed less than 7/8” above the roof

33C (60F) shall be added to the ambient temperature before applying the derate factor in Table 310.15(B)(2)(a)

149 Select the derate column according to

the conductor.

Conductor ampacity must be derated for more than three current-carrying conductors together in a conduit or cable for more than 24”.

For DC, both positive and negative are current carrying conductors.

For AC, the neutral is considered current carrying only if the circuit contains non-linear loads.

Table 310.15(B)(3)(a) Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable.

150

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Review: Calculations for Conductor Sizing and DeratingPV DC conductors:

1. Isc x 1.25 = Maximum current (maximum continuous current)

2. Max current x 1.25 = minimum conductor rating - Table 310.15(B)(16)

e.g. PV array with module Isc 9a

Isc 9a x 1.25 x = 11.25a max continuous string current

11.25a x 1.25 = 14.06a = output conductor ampacity requirement

3. Select conductor based on equipment and conductor temperature rating.

Table 310.15(B)(16) shows #14 is adequately rated in the all columns.

4. Apply derate factors for temperature and # of conductors in a conduit.

Table 69031(A) for temperature and Table 310.15(B)(3)(a) for # of conductors

e.g. Ambient temperature of 110°F and 4 conductors in a conduit (2 strings)

Equipment and conductor are 90 rated

#14 is rated 25a in the 90C column

25a x .87 x .80 = 17.4a

17.4 a is greater than 11.25a max current calculated in #2 above.151

Voltage Drop Calculations

Table 8 lists conductor resistance per 1000 feet for conductors in DC circuits.

• Find the wire size and corresponding resistance (Ohms/kFT) uncoated for copper.

• Determine the operating current (STC Imp x 80% or NOC Imp)

VD = operating current x one way distance x 2 ÷ 1000 x Ohms/kFT

VD% = VD ÷ operating voltage (NOC Vmp x # of modules in string)

Table 9 has resistances per 1000 feet for AC conductors.

• Use inverter continuous current listed on data sheet

3-phase calculation

VD = operating current x one way distance x 1.732 ÷ 1000 x Ohms/kFT

1.732 is the square root of 3 (√3)

In AC systems, voltage drop should be no more than 3% and shall not be more than 5%. This is because as voltage drops amperage increases.

PV array DC output voltage drop does not affect amperage. We try to limit voltage drop to less than 2% and no more than 3% in order to maximize system output.

152

STC-NOCSlide 10

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153

Table 8 DC Conductor Properties

154

Table 9 Alternating Current Resistance

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Review: Voltage Drop Calculations

155

First gather the necessary information to make the calculation.

1. Find the operating current.

• Module STC Imp x 80% or NOC Imp (single string or combined strings)

• For inverter output, the continuous current is used.

2. Determine the length of the conductor in the circuit.

3. Look up the Ohms/kFT in Chapter 9 Table 8 for DC or Table 9 for AC.

4. Find the operating voltage

• Module NOC Vmp on data sheet x # in series

• Inverter or premises AC nominal voltage

5. Put the information in the formula and calculate

Example: Module NOC Imp 7.76a and Vmp 29v 13 modules in a string

Conductor length 60’ #14 AWG

VD = 7.76a x 60’ x 2 x 3.14Ω/kFT ÷ 1000 = 2.92v

String voltage = 29v x 13 in series = 377v

VD% = 2.92v ÷ 403v = .0074 or .74%

156

690.9 Overcurrent Protection.

(A) Circuits and Equipment. PV system dc circuit and inverter output conductors and equipment shall be protected against overcurrent. Overcurrent protective devices are required where currents exceed the rated capacity of equipment or conductors.

Exceptions: A PV circuit overcurrent device is not required in the following conditions.

(1) Where there are no parallel external source circuits such as other module strings, batteries or back-fed current from inverters.

This would be a single string of modules connected to a string inverter or a single module connected to either a DC-DC converter or a micro-inverter.

(2) The short-circuit currents from all sources do not exceed the ampacity of the conductors and overcurrent device rating for the PV module or dc-to-dc converter.

e.g. PV module with Isc of 6a and series fuse rating of 15a.Two strings connected in parallel without a fuse. 2 x 6a = 12a12a is less than 15a so no fuse is required.

With ungrounded systems, only one of the two DC conductors requires a OCD or fuse a long as a disconnect is in place that disconnects both conductors simultaneously.

Overcurrent Protection Requirements

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690.9 Overcurrent Protection cont.

(B) Overcurrent Device Ratings. OCDs used with PV DC circuits must be listed for use with PV systems and are to be sized in 1, 2 or 3 below.

(1) Not less than 125 percent of the maximum currents calculated in 690.8(A).

e.g. Isc x 125% x 125%

(C) Photovoltaic Source and Output Circuits. A single overcurrent protective device shall be permitted to protect the PV modules and conductors of each source circuit or the conductors of each output circuit.

• All overcurrent devices OCDs shall be placed in the same polarity for all circuits within a PV system.

• The OCD shall be accessible but shall not be required to be readily accessible.

Art. 240.6(A) Fuses and Fixed-Trip Circuit Breakers.

Table 240.6(A) Standard Ampere Ratings for Fuses and Inverse Time Circuit Breakers

DC fuses under 15a: 1a – 10a and 12a

The standard ampere ratings for fuses 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes.

DC Overcurrent Protection

Check the listing for the OCD used with PV system DC circuits. It must be listed for PV DC circuits.

The UL 2579 class of fuses include Class R, J and M.

Recommended fast blow fuses for PV source and output circuits

Large capacity high voltage breakers are becoming more of a standard on PV systems with central inverters.

600 volt DC

M-class fuses

1 -30 amps

600 volt DC

R-class fuses

30 to 350 amps158

150 volt DC breakersUsed primarily on battery systems

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• 14 AWG Copper. 15 amp OCD

• 12 AWG Copper. 20 amp OCD

• 10 AWG Copper. 30 amp OCD

240.4(D) Small conductors

Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by ratings listed below after any correction factors for ambient temperature and number of conductors have been applied.

Overcurrent Device OCD Rating and Conductor Rating

240.4(B) Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:

240.4(C) Overcurrent Devices Rated over 800 amperes (1MW inverters)Where the overcurrent device is rated over 800 amperes, the ampacity of the conductors it protects shall be equal to or greater than the rating of the overcurrent device defined in 240.6.

159 The conductor size can be now smaller than shown above for each OCD.

160

Exercise Example: (Use tables on next page)

36 - 250w modules: 3 strings: 12 in series Voc 36v : Vmp 30.5v : Isc 8.9a : Imp 8.2a

CombinerPV array Inverter

8kW 1-Phase reverse current protected7600w 240v 32a

AC panel

1. Give the string max current rating.

2. Give the string fuse requirement.

3. Give the string conductor ampacity requirement.

4. Select the minimum size conductor from the j-box to the combiner.

5. What is the ampacity rating of the selected conductor?

6. Derate the string conductors for conditions.

7. What is the OCD requirement of the inverter output?

8. Size the inverter output conductor.

[-----------------------max temp. 37ºC------------------------] [----------max temp. 30ºC-----------]

DC & AC Terminals

Rated 75ºC

J-box

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Table 310.15 (B)(16) 3 conductors in a raceway at 30°C.

161

Table 310.15(B)(3)(a) Adjustment for More Than Three Current-Carrying Conductors in a Raceway.

Table 690.31(A) Correction Factors

162

Exercise Example answers:

36 - 250w modules: 3 strings: 12 in series Voc 36v : Vmp 30.5v : Isc 8.9a : Imp 8.2a

CombinerPV array Inverter

8kW 1-Phase reverse current protected7600w 240v 32a

AC panel

1. Give the string max current rating. 8.9a x 1.25 x = 11.25a

2. Give the string fuse requirement. 11.25 x 1.25 = 13.9 15a OCD Table 240.6(A)

3. Give the string conductor ampacity requirement. 11.25 x 1.25 = 13.9 14a

4. Select the minimum size conductor from the j-box to the combiner. #14

5. What is the ampacity rating of the selected conductor? 20a Table 310.15(B)(16) 75º

6. Derate the string conductors for conditions. 20a x .91 x .80 = 14.56a > 11.25a Table 310.15 (B)(2)(a) and Table 310.15(B)(3)(a)

7. What is the OCD requirement of the inverter output? 32a x 1.25 = 40a 240.6(A)

8. Size the inverter output conductor. 32 x 1.25 = 40a #8 Table 310.15(B)(16) 75º

[-----------------------max temp. 37ºC------------------------] [----------max temp. 30ºC-----------]

DC & AC Terminals

Rated 75ºC

J-box

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163

Review on Conductor and Overcurrent Device selection

Table 400.4 provides conductor properties and conditions of use.

The minimum bending radius for USE and USE-2 is 5x the conductor diameter.

PV source and output maximum current is 125% of the STC short circuit current Isc.

A professional electrical engineer can make an alternate calculation using the highest 3-hour irradiance for the location; it can be no less than 70% of (125% of STC) method.

For interactive inverters the continuous current is the listed max current.

Conductors and circuit requirements must be rated no less than 125% of continuous current.

Conductor selection is based on the ampacity under the temperature rating of the conductor and the connected equipment. The lowest temperature column is to be selected.

Conductor ampacity must also be derated if 10% or 10’ of its length is exposed to conditions other than the ratings of Table 310.15(B)16.

PV source and output conductor ampacities are derated for temperature using Table 690.41(A) if they are exposed to temperatures greater than 30C (68F).

Other conductor ampacities are derated using Table 310.15(B)(2)(a)

Conductors in conduit less than 7/8” above a roof and exposed to sunlight must add 33C

164

Review: Conductor and Overcurrent Device selection

Conductors ran in conduit for more than 24 inches must be further derated in Table 310.15(B)(3)(a) if there are more than 3 current carrying conductors in the conduit.

Voltage drop occurs over a length of wire when current passes through it. Table 8 is used for DC circuits to select conductor ohms/kFT for this calculation.e.g. VD = operating current x one way distance x 2 ÷ 1000 x Ohms/kFT

AC circuits use Table 9 for the same formula. 3-phase circuits use the following formula.VD = operating current x one way distance x 1.732 ÷ 1000 x Ohms/kFT

For high ampacity requirements parallel conducts can be used instead of a single conductor.

• The parallel conductors can be no smaller than 1/0 AWG.

• They must be the same length, size, type and be terminated in the same manner.

Overcurrent devices (OCD) are sized 125% grated than the continuous current. Table 240.6(A) provides increments for OCDs.

Conductor ampacities of the following must match the OCD.

• 14 AWG Copper. 15 amp OCD

• 12 AWG Copper. 20 amp OCD

• 10 AWG Copper. 30 amp OCD

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1. Bending radius to tight for USE-2 and PV wire.

2. Selection of the wrong type of conductor insulation for underground conduit.

3. Violations of small conductor and OCD maximums. (#14 – 15a, #12 – 20a, #10 – 30a)

4. Failing to follow manufacturer’s required ampacities and OCDs in manual.

Most common violations

Addressing this potential violation.

1. The minimum bending radius is 5x the conductor diameter for USE-2; several high voltage conductors such as PV wire have a bending radius of 8x.

− If you can’t fit a coffee cup into the curve, it is in violation.

2. THHN is sometimes used and it is OK for moist locations but not wet. THWN-2 or XHHW-2 are commonly used for underground. List it on the permit.

3. The conductor-OCD violation occurs most often with residential inverter output conductors. For these three conductors, the OCD must be determined and the conductor is selected and can be no smaller than shown in Article 240.4(D). List it on the permit.

4. The manufacture may override the NEC calculations for conductors and OCDs; if so the installer must adhere to those specifications.

− This is most common with battery system inverter input and output.

690.31 Methods Permitted.

(A) Wiring Systems. Where PV source and output circuits operating at voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be guarded or installed in Type MC cable or in raceway.

Ground mounted arrays with source wires lower than 8’ must provide guarding.

Definition: Guarded. Covered, shielded, fenced, enclosed, or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to remove the likelihood of contact by persons to a point of danger.

Examples:

Residential ground mounted array

• A 4’’ fence 6’’ away from the array.

• Metal or 30 year UV rated fabric mesh preventing access to the source conductors.

Commercial ground and roof mount

• 6’ fence 10’ from the array for ground mounts

• Roof array with unauthorized access will require a barrier or enclosed racking.

e.g. Solar Dock racking is totally enclosed.

Conductor Protection

166

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690.31 (C) Single -Conductor Cable (1) General. Single conductor USE-2 and “PV wire” are permitted for PV source and

output conductors and shall be installed according to 338.10(B)(4)(b) and 334.30.(2) Cable Trey. The use of cable trey used outdoors is permitted when the cables are

supported at least every 12 inches and secured at least every 4.5 ft.

167

Article 338.10 Uses Permitted.

(B)(4)(b) Exterior Installations. Service-entrance cable used for feeders or branch circuits, where installed as exterior wiring, shall be installed in accordance with Part I of Article 225. The cable shall be supported in accordance with 334.30.

334.30 Securing and Supporting.

Nonmetallic-sheathed cable shall be supported or secured 4½ ft and within 12 in. of every outlet box, junction box, cabinet, or fitting.

PV cables must be secured within 12” of the module j-box and any other J-box.

• This is almost impossible to achieve with some module j-box locations.

The 4 ½ ft requirement should be reduced to 24” .

PV source conductor securing and supporting

(G) Direct-Current Photovoltaic Source and Output Circuits on or in a Building.

Where direct-current photovoltaic source or output circuits of a utility-interactive inverter from a building-integrated or other photovoltaic system are run inside a building or structure, they shall be contained in metal raceways from the point of penetration of the surface of the building or structure to the first readily accessible disconnecting means.

The wiring methods shall comply with the additional installation requirements in (1) through (4)listed on the next page.

Art.690.31 Wiring Methods

Protection Against Fire From DC Conductors

FMC and MC cable are the most common metallic conduit used for residential installations.

EMT and IMC are commonly used on commercial buildings 168

This area

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690.31(G) Direct-Current PV Source and DC Output Circuits on or in a Building.

Routing of PV Source Conductors

169

(2) Flexible Wiring Methods. Flexible metal conduit FMC shall be protected if smaller than ¾ inch.

Metal clad conduit MC shall be protected if smaller than 1 inch by substantial guard strips that are at least as high as the raceway or cable.

It is common to run one or the other of these two in residential attics and basements.

1” and larger MC cable needs no protection

¾” and larger FMC cable needs no protection

(3) Marking or Labeling Required. A label “Warning: Photovoltaic Power Source” shall be installed where: (1) Exposed raceways, cable trays, and other wiring methods(2) Covers or enclosures of pull boxes and junction boxes(3) Conduit bodies in which any of the available conduit openings are unused

(4) Marking and Labeling Methods and Locations. The labels shall be visible and rated for their environment. The labels shall be placed on all PV wireways at all observable points and at intervals of no more than 10 feet.

Article 690.31(G) continued

170

The labels shall be reflective, and all letters shall be capitalized and shall be a minimum height of 9.5 mm (3⁄8 in.) in white on a red background.

This is only on PV source and output circuits that are on or inside a building.

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Which Conduit for the Application?

PVC is usually used for ground mounted systems with underground feeds.

• When PVC is used for above ground feeds the issue of expansion should be considered due to extremes of temperature.

• If PVC is used when exposed to physical damage it must be protected or Schedule 80 is required.

FMC or MC is usually used for residential interior installation wile commercial typically use EMT for interior applications.

EMT, IMC or RMC are used on most rooftop installations

• EMT uses compression connectors and although they are rated for over 250v as grounding pathway they are subject to connector failure if expansion couplings are not used in exterior installations with long runs.

• If EMT is used in locations where it will be exposed to physical damage it must be protected.

• IMT or RMC are typical used for large commercial exterior applications; they are both rated against physical damage and have low expansion rates due to temperature swings.

Annex C provides conduit fill for # of conductors and type of conductor insulation.

171

PV source and output circuit conductors operating over 30v must be protected from ready access by unauthorized persons. They must be guarded by boxes, conduit or some type of obstruction to prevent accidental contact.

Where multiple different circuits are ran in the same raceway or conduit, they must be separately identified at junction boxes.

• In cable treys the separate identification must occur no less than every 6 feet.

PV wire and USE-2 source conductors must be secured within 12 inches of j-boxes and every 4 ½ ft in between.

PV array source and output conductors ran on or in a building must be ran in metal raceways up to the first readily accessible disconnect.

• If MC cable is ran in accessible locations, it must be protected if smaller than 1”

• If FMC conduct is ran in accessible locations, it must be protected if smaller than 3/4”

PV source and output conduit ran on or in building must be marked with the following.

WARNING: PHOTOVOLTAIC POWER SOURCE

172

Review: PV Array Output Conductor Protection

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1. Residential ground mounted array source conductors are often not adequately protected from unauthorized ready access.

2. Separate circuits are not adequately separated or identified at j-boxes or pull boxes.

3. Residential rooftop source conductors are not adequately secured to modules or railing.

4. The label Warning: Photovoltaic Power Source is often forgotten on residential installs.

5. PVC conduit used for PV source and output circuit conductors.

Most common violations

Addressing this potential violation.

1. If you can reach the conductors by hand without removing the barrier or standing on a ladder, it is in violation.

2. This is common in j-boxes without terminations. Have the contractor remove the j-box cover to inspect for multiple circuits that are not identified or separated.

3. It is usually possible to look at the array from the plane of the roof; a high powered flashlight may be necessary to see wire sags under the array.

4. Look for the label on PV array output circuits attached to the building or ran into the building. This easy to see or not see as the case may be.

5. PVC is OK from the inverter output but not to the inverter input if the conduit enters the structure. This will only occur on residential installations.

690.11 Arc-Fault Circuit Protection (Direct Current).

Photovoltaic systems operating at 80 volts or greater, shall be protected by a listed PV arc-fault circuit interrupter or other system components listed to provide equivalent protection.

• The system shall detect and interrupt arcing faults resulting from a failure of continuity in a conductor, connection, module, or other component in the PV system dc circuits.

• 2014 NEC also required these on ground mounted systems.

Exception: For PV systems not installed on or in buildings:

• PV output circuits and dc-to-dc converter output circuits that are direct buried, installed in metallic raceways, or installed in enclosed metallic cable trays are permitted without arc-fault circuit protection.

• Detached structures whose sole purpose is to house PV system equipment are also permitted without arc-fault circuit protection.

2011 Arc-fault Protection Requirements

174

The device must meet the UL1699B standard.

It may be located in inverters, combiners, module optimizers or in DC wiring fuse boxes or charge controllers for battery based systems.

Protection from Arcs and Requirements for First Responders

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110.16 Arc-Flash Hazard Warning.

(A) General. Any location other than dwelling units where service may be performed while the conductive parts are energized must be marked to warn of arc-flash potential.

Protection Against Arc-Flash

175

The warning sign(s) or label(s) shall comply with 110.21(B).

(B) Service Equipment For 1200a rated equipment, a label with the following must be in place.

(1) Nominal voltage

(2) Available fault current at overcurrent devices OCD

(3) clearing time of OCD

(4) Date label was applied

A 50kW string inverter would be a class 1.

176

Example formula: Combiner, DC disconnect or Recombiner box arc-flash formula

(Pmax x 125% x 2 second ÷ (4πD²) x 3 x .239cal/J) = cal/cm²• D = distance 18” (45.5cm) arc-flash standard distance• 3 is a multiplier used for enclosures with open front only.• 1.2 cal/m² and greater require arc-flash protection

e.g. 50kW X 125% x 2 ÷ 26002 x 3 x .239 = 3.45cal/cm²

Arc flash classifications

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177

Service equipment fault current marking

110.24 Available Fault Current (A) Marking. Service equipment for other than dwelling units must field-mark the max available fault current even if it is not assessable when live.

This would only be required if the commercial PV system is connected to the line side of the meter as a separate service. e.g. (Georgia Power Tariff program)

When transformers are used this calculation also includes the impedance of the transformer.

e.g. Transformer kW ÷ 1000 ÷ voltage ÷ 1.732 ÷ impedance

500kW x 1000 ÷ 480v ÷ 1.732 ÷ .05Ω = 12,028a fault current

Lockable Disconnects

110.25 Lockable Disconnecting Means. If a disconnecting means is required to be “lockable open” elsewhere in this Code, it shall be capable of being locked in the open position under all conditions.

Open

Lockable

178

690.12 Rapid Shutdown of PV Systems on Buildings

PV system circuits installed on or in building shall include a rapid shutdown function to reduce shock hazard for emergency responders in accordance with 690.12(A) through (D).

Exception: Ground mounted PV system circuits that enter buildings dedicated only for PV system equipment shall not be required to comply with 690.12.

The following is the 2014 version which has been changed or moved in the 2017 version.

1. Requirements for controlled conductors shall apply only to PV system conductors of more than 1.5 m (5 ft) in length inside a building, or more than 3 m (10 ft) from a PV array.

2. Controlled conductors shall be limited to not more than 30 volts and 240 volt-amperes within 10 seconds of rapid shutdown initiation.

3. Voltage and power shall be measured between any two conductors and between any conductor and ground.

4. The rapid shutdown initiation methods shall be labeled in accordance with 690.56(C).

5. Equipment that performs the rapid shutdown shall be listed and identified.

Rapid Shutdown of the DC Side of the PV System

2017 changes and additions (A) through (D) are on the following slides

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179

2017 NEC version of 690.12(A) through (D).

(A)Controlled Conductors. Requirements for controlled conductors shall apply to all PV array source and output circuits.

(B) Controlled Limits. The array boundary is defined here as 305 mm (1 ft) from the array in all directions.

(1) Outside the Array Boundary. Controlled conductors located outside the boundary or more than 1 m (3 ft) from the point of entry inside a building shall be limited to not more than 30 volts within 30 seconds of rapid shutdown initiation.

• Voltage shall be measured between any two conductors or conductor to ground.

(2) Inside the Array Boundary. The PV system shall comply with one of the following:

(1) The PV array shall be listed or field labeled as a rapid shutdown PV array.

• The PV array shall be installed and used in accordance with its instructions.

(2) Controlled conductors shall be limited to not more than 80 volts within 30 seconds of rapid shutdown initiation.

• Voltage is between any two conductors or conductor to ground.

(3) PV arrays with no exposed wiring or conductive parts installed more than 2.5 m (8 ft) from exposed grounded parts are not be required to comply with (B)(2).

690.12(B)(2) shall become effective January 1, 2019.

180Credit: May/June SolarPro article written by Bill Brooks

Outside the boundary reduced to 30v within 30 sec.

• 2014 boundary is 5’ inside or 10’ outside the building

• 2017 boundary is 3’ inside or 1’ outside the building

Inside the boundary reduced to 80v will not take effect until January 1st 2019

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181

(C) Initiation device. The device shall initiate the rapid shutdown function of the PV system. Its “off” position shall indicate that the rapid shutdown function has been initiated for all PV systems connected to that device.

• For one-family and two-family dwellings, an initiation device(s) shall be located at a readily accessible location outside the building.

• The initiation device(s) shall consist of at least one of the following:

(1) Service disconnecting means

(2) PV system disconnecting means

(3) Readily accessible switch that plainly indicates whether it is “off” or “on”.

This may be the PV system AC disconnect, DC disconnect or a remote activation device that is listed specifically for rapid shutdown of PV circuits.

• As with all service disconnects, the number cannot exceed more than 6 separate switches to disconnect all PV system circuits for a single service customer.

The would most like only occur with a central inverter that has multiple combiner boxes containing rapid shutdown devices.

• Since string inverters are typically used, this situation is unlikely.

2017 NEC version of 690.12(A) through (D) cont.

182

(D)Equipment. Equipment that performs the rapid shutdown functions, other than listed disconnect switches, circuit breakers, or control switches, shall be listed for providing rapid shutdown protection.

Informational Note: Inverter input circuit conductors often remain energized for up to 5 minutes with inverters not listed for rapid shutdown.

This refers to the 2019 requirement of 80v or less inside the 1 ft. boundary

All commercial string inverters located within 1 ft. of the array are in compliance (until 2019) if the AC disconnect is placed in a readily accessible location.

AC disconnects shut down micro-inverters within 1 foot of the array

Listed Rapid Shutdown devices disconnect DC circuits within 1 ft. of the array

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183

Review: Protection with Arcs, Faults and First Responders

AFCI devices are required on all roof mounted PV arrays operating at 80v and over.

Arc-flash warnings are required on any location other than dwelling units where service may be performed on live electrical parts.

Service equipment other than for dwelling units must be marked for the available fault current even if it is not accessible when live.

PV systems installed buildings must be equipped with a rapid shutdown function.

• The 2014 version allows 10’ from the array boundary to the location of the disconnect for the exterior and 5’ to the interior.

• The 2017 version allows 1’ from the array boundary to the location of the disconnect for the exterior and 3’ to the interior.

− The disconnect must be remotely activated from a readily accessible location.

NOTE:

• Micro-inverters all perform the rapid shutdown function upon loss of AC power.

• SolarEdge inverters all perform this function by use of their module PV optimizers.

• Tigo electronics has a UL listed device that snaps onto the module junction box and provides the rapid shutdown function to several inverter brands.

184

1. Arc-fault device missing from battery based system.

2. Arc Flash warning not posted on commercial AC switchgear.

3. Rapid shutdown switch not labeled and posted.

Most common violations

Addressing this potential violation.

1. Arc-fault devices are standard in residential interactive inverters and most commercial interactive inverters.

− With battery systems, the device may be in the charge controller of a separate device placed in a combiner box or the DC output box. Require the contractor to list where the device is located on the permit and/or drawings.

2. There may not be an arc flash potential with small commercial system but the medium sized 100kW to 1MW are likely to require them. Since string inverters are used for non-utility scale systems, the DC side usually has low potential when serviceable.

3. This is the #1 mostly likely violation! Interactive systems usually comply with the device since residential rooftop systems are either micro-inverters or SolarEdge optimized and commercial string inverters are located on the roof with the PV array.

− The 2014 requirement for posting the label was very vague. The 2017 is very clear; they switch that initiate the shutdown must be marked.

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Disconnect Requirements from the PV System

690.13 (A) Location. The PV System disconnecting means shall be installed at a readily-accessible location.

This 2014 exception no longer applies in the 2017 NEC since rapid shutdown must occur within 1’ of the PV array.

Informational Note: PV systems installed in accordance with 690.12 address the concerns related to energized PV array DC conductors entering a building.

PV system disconnect means does not always refer to PV array DC conductors.

• The following sides will identify various locations of the PV system disconnect means for different systems.

III. Disconnecting Means

690.13 Photovoltaic System Disconnecting Means. Means shall be provided to disconnect the PV system from all wiring systems including power systems, energy storage systems, and utilization equipment and its associated premises wiring.

The former reference to ungrounded conductors has been removed in the 2017

185

186Drawing credit: May/June SolarPro article written by Bill Brooks

Micro‐inverters or AC modules

Interactive PV system disconnect means

Micro-inverters or AC modules: The AC disconnect is the PV system disconnect means.

String inverters also use an AC disconnect as the PV system disconnect means.

PV array DCDisconnect

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187

PV systems with energy storage disconnect means

DC coupled PV systems with energy storage: The DC disconnect the PV system disconnect.

Energy Storage Disc.

AC coupled PV systems with energy storage: • The interactive inverter AC disconnect the PV system disconnect.

Drawing credit: May/June SolarPro article written by Bill Brooks

690.13 (B) Marking. Each PV system disconnecting means shall plainly indicate whether in the open (off) or closed (on) position and be permanently marked “PV SYSTEM DISCONNECT” or equivalent.

188

Additional markings shall be permitted basedupon the specific system configuration.

For PV system disconnecting means where the line and load terminals may be energized in the open position, the device shall be marked with the following words or equivalent:

This is most likely to occur on systems with central inverters with disconnects from multiple DC combiner boxes.

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(C) Suitable for Use: If the PV system is connected to the supply side of the service disconnecting means as permitted in 230.82(6), the PV system disconnecting means shall be listed as suitable for use as service equipment.

The minimum rating for supply side disconnects is 60a

(D) Maximum number of disconnects. Each PV system disconnecting means shall consist of not more than six switches or six sets of circuit breakers.

• A single PV system disconnecting means shall be permitted for the combined ac output of one or more inverters.

This article was reworded for clarity. The purpose of this requirement is to provide quick shutdown of a PV system.

(E) Ratings. The PV system disconnecting means shall have ratings sufficient for the maximum available short-circuit current, and voltage connect to it.

(F) (1) Simultaneous Disconnection. The PV system disconnecting means shall simultaneously disconnect the PV system conductors from all other conductors.

• Types: Externally operable switch, circuit breaker, or other approved means.

• A dc PV system disconnecting means shall be marked for use in PV systems or be suitable for backfeed operation.

189 This includes functionally grounded conductors.

190

690.13(D) illustrated

Each of these inverters requires a separate overcurrent device which is also a disconnect.

• Since there are more than 6, a combined circuit disconnect must be provided.

• In this picture there are 16 inverters with OCD disconnects; they must be combined into groups of 3 or more to reduce the total number of disconnects to 6 or less.

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(A) Location. Isolating devices shall be installed within sight of and within 10 ft of the equipment.

• An equipment disconnecting means shall be permitted to be located further away if it remotely activates a disconnect located within 3 m (10 ft) of the equipment.

(B) Interrupting Rating. An equipment disconnecting means shall have an interrupting rating sufficient for the maximum short-circuit current and voltage available at the terminals.

• An isolating device shall not be required to have an interrupting rating.

These isolating devices can be non-load-rated.

Art.690.15 Disconnection of Photovoltaic Equipment. Isolating devices shall be provided to isolate PV modules, ac PV modules, fuses, dc-to-dc converters inverters, and charge controllers from all conductors that are not solidly grounded. This refers to connectors such as PV module polarized type and micro-inverter

connectors rated less than 30a. Circuits of 30a and greater must use a listed load-rate disconnecting means.

191PV module isolating connectors

Micro-inverter isolating connectors

Load rated disconnect

192

Readily accessible

690.15(A)

Modules are connected to each other or electronic equipment with listed isolating devices (polarized connectors)

Micro inverters are located beneath PV modules and are attached to each other with listed isolating connectors.

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690.15(C) Isolating Device. An isolating device shall not be required to simultaneously disconnect all current-carrying conductors of a circuit.

• The isolating device shall be one of the following:

(1) A connector meeting the requirements of 690.33 and listed for the use.

This reference is to polarized connectors that are touch safe with latching connections and are listed for the use.

(2) A finger safe fuse holder

Both devices at right meetthis designation.

(3) An isolating switch that requires a tool to open

(4) An isolating device listed for the intended application

• Non-load-rated isolating device shall be marked “Do Not Disconnect Under Load” or “Not for Current Interrupting.”

193

(D) Equipment Disconnecting Means. An equipment disconnecting means shall simultaneously disconnect all current carrying conductors that are not solidly grounded of the circuit to which it is connected.

The grounded conductor in a grounded PV system must be switched with the ungrounded conductor if it is grounded with a GFDI. (BIG CHANGE)

• An equipment disconnecting means shall be safely externally operable.

• The disconnect shall indicate whether in the open (off) or closed (on) position, and be lockable in the open (off) position.

• An equipment disconnecting means shall be one of the following devices:

(1) A manually operable switch or circuit breaker

(2) A connector meeting the requirements of 690.33(E)(1)

Be rated for interrupting current without hazard to the operator

(3) A load break fused pull out switch

(4) A remote-controlled circuit breaker that is operable locally and opens automatically when control power is interrupted

This would most likely be a rapid shutdown switch.

194

This 2017 NEC sub-article (D) has replaced 2014 NEC article 690.17.

Note the requirement to disconnect both + and – conductors in all systems

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195

690.15(D) illustrated

Grounded PV systems have historically required the grounded conductor to be marked white or grey and placing a disconnect in this conductor was very restrictive.

• Now the grounded conductor is not to be marked white or gray and it must be disconnected simultaneously with the ungrounded conductor.

2014 NEC and earlier grounded PV2017 NEC grounded and ungrounded PV

NOTE: The grounded conductor is functionalgrounded, not solidlygrounded.

196

Review: Disconnect Requirements

It is required to have a means to disconnect the PV system from all other components and systems.

The PV system disconnect means shall be located at a readily accessible location.

• With interactive PV system that location is at the interactive inverter disconnect.

• With battery based PV system that location is the PV array DC disconnect.

Each PV system disconnect must be marked PV SYSTEM DISCONNECT

For disconnects where the line and load terminals can remain energized in the off position, the following notice must be posted. WARNING: ELECTRIC SHOCK HAZARD

TERMINALS ON THE LINE AND LOAD SIDE MAY BE ENERGIZED IN THE OPEN POSITION

The PV system disconnect means shall consist of not more than 6 switches.

The PV system disconnecting means must be externally operable.

The PV system disconnecting means must disconnected all conductors that are not solidly grounded simultaneously.

Isolating devices such as polarized PV connectors serve as non-load breaking disconnects.

Isolating devices must be located within-sight-of and within 10’ of the equipment.

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197

Review: Disconnect Requirements, cont.

The 2014 code does not allow for a disconnect in the grounded conductor.

The 2017 code requires a disconnect in the grounded conductor if it is a functional ground such as in a GFDI fuse.

• With PV circuits, the + and – conductors must be simultaneously disconnected. The conductors should be marked red (+) and black (-) even if one is functionally grounded.

198

1. Disconnects may serve several functions and require several labels. One of the required labels is usually missing when this is the case.

2. More than 6 PV system disconnects are more common now with commercial string inverter systems.

Most common violations

Addressing this potential violation.

1. Interactive systems use the AC disconnect as PV system disconnect (1); it is most likely the rapid shutdown switch as well (2). The disconnect must also list the AC operating voltage and current (3). The utility will also place a label on the disconnect. (3 labels +)

− DC coupled battery PV systems use the DC disconnect as the PV system disconnect (1); it may also be the rapid shutdown switch (2). The disconnect must also show the array max voltage and current and the charge controller max current (3). (3labels)

2. This is easy to see since the AC disconnect is located next to the inverter. It they all feed into a dedicated switchgear panel, a main AC switch will disconnect them all.

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199

110.21(B) Field-Applied Hazard Markings.

(1) The marking shall adequately warn of the hazards using effective words and/or colors and/or symbols or any combination thereof.

Informational Note: ANSI Z535.4-2011, Product Safety Signs and Labels, provides guidelines for suitable font sizes, words, colors, symbols, and location for labels.

(2) The label shall be permanently affixed to the equipment or wiring method and shall not be hand written.

Exception: Portions of labels or markings that are variable, or that could be subject to changes, shall be permitted to be hand written and shall be legible.

All PV labels should be printed.

(3) The label shall be of sufficient durability to withstand the environment involved.

Consider the life of the PV system.

NOTE: Several companies offer labeling serviced: “PV Labels”, “HellermannTyton” and some of the solar distributors are now offering this service.

PV System Labels and Plaques

(1) Rated maximum power-point current (2) Rated maximum power-point voltage (3) Maximum system voltage

(open voltage on coldest day of year)(4) Maximum circuit current (5) Maximum rated output current of the

charge controller (if installed)

690.53 Direct-Current Photovoltaic Power Source.

A permanent label for the direct-current photovoltaic power source indicating items (1) through (5) shall be provided by the installer at the photovoltaic disconnecting means:

2014 Labeling Requirement for PV Array DC Disconnects

The following slide represents the 2017 version of this article. 200

#1 is the STC Imp x # of strings in parallel

#2 is STC Vmp x # of module is series

#3 is Voc x # of modules is series x the coldest day temperature coefficient factor.

#4 is to be the maximum continuous current (Isc x 125%)

#5 is the max current listed on the charge controller

MAXIMUM CIRCUIT CURRENT

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(1) Maximum system voltage (open voltage on coldest day of year)

(2) Maximum circuit current (3) Maximum rated output current of the

charge controller (if installed)

690.53 Direct-Current Photovoltaic Power Source.

A permanent label for the direct-current photovoltaic power source indicating items (1) through (3) shall be provided by the installer at each load rated photovoltaic disconnecting means: • Each DC power source must have this label

2017 Labeling Requirement for PV Array DC Disconnects

201

MAXIMUM CIRCUIT CURRENT

#1 is Voc x # of modules is series x the coldest day temperature coefficient factor.

#2 is to be the maximum continuous current (Isc x 125%).

#3 is the max current listed on the charge controller.

The other two values we removed because they are insignificant to inspectors, first responders or service personnel..

690.54 Interactive System Point of Interconnection. All interactive system(s) points of interconnection with other sources shall be marked at an accessible location at the disconnecting means as a power source and with the rated ac output current and the nominal operating ac voltage.

202

Labeling on the Inverter AC Disconnects

This is the utility voltage and the inverter rated continuous current.

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Identification of Power Sources 690.56

690.56(A) Facilities with Stand-Alone Systems. Any structure or building with a photovoltaic power system that is not connected to a utility service source and is a stand-alone system shall have a permanent plaque or directory installed on the exterior of the building or structure at a readily visible location acceptable to the authority having jurisdiction.

• The plaque or directory shall indicate the location of system disconnecting means and that the structure contains a stand-alone electrical power system.

• The marking shall be in accordance with 690.31(G).

Readily visible indicates a location that is visible from the main approach to the facility. i.e. as you drive up

203

THIS STRUCTURE CONTAINS A STAND ALONE

ELECTRICAL PV SYSTEM

PV SYSTEM DISCONNECT IS LOCATED

________________

9.5 mm (3⁄8 in.)letting

White letters on red background

Identification of Power Sources

690.56(B) Facilities with Utility Services and PV Systems. Removed from 690 in the 2017 NEC because it is duplicated in Article 705.10

204

If the PV system AC disconnect is located next to the service equipment location, the label on the disconnect is sufficient.

The directory can be in writing instead of a drawing.

• Using both is a better form of communication.

705.10 Directory. A permanent plaque or directory denoting the location of all electric power sources disconnecting means on or in the premises shall be installed at each service equipment location and at the disconnect(s) for each electric power production source capable of being interconnected. • The marking shall comply with 110.21(B).

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2014 version of 690.56(C): Rapid Shutdown Label Requirement

690.56(C) Facilities with Rapid Shutdown. Buildings or structures with both utility and PV system complying with 690.12 shall have a permanent plaque or directory including the following wording:

The plaque shall be reflective with all letters capitalized and having a minimum height of 3/8 inches in white on red background.

205

Effective until 2017 NEC is adopted

No designation for the location of the label

2017 version of 690.56(C): Rapid Shutdown Label Requirement

690.56(C) Buildings with Rapid Shutdown. Buildings with PV systems shall have permanent labels as described in (1) through (3) below.

(1) Rapid Shutdown Type. The type of rapid shutdown shall be labeled as in (a) or (b):

(a) For PV systems that shut down the array internally and conductors leaving the array: Use the following language

206

SOLAR PV SYSTEM EQUIPPED

WITH RAPID SHUTDOWN

Minimum3/8” letter heightBlack letters on yellow background

Minimum3/16” letter heightBlack letters on white background

Label shall be located no more than 3 ft from the service disconnecting means.

Effective on January 1st 2019

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(1) Rapid Shutdown Type. The type of rapid shutdown shall be labeled as described in (a) or (b) below:

(b) For PV systems that only shut down conductors leaving the array:

207

Minimum3/8” letter heightWhite letters on Red background

Minimum3/16” letter heightBlack letters on white background

SOLAR PV SYSTEM EQUIPPED

WITH RAPID SHUTDOWN

The labels in (1)(a) and (b) shall include a simple diagram of a building with a roof. • The diagram shall have sections in red to signify areas of the PV system that are not

shut down when the rapid shutdown switch is operated.

SOLAR ELECTRICPV PANELS

Effective when 2017 NEC is adopted

Label shall be located no more than 3 ft from the service disconnecting means.

690.56(C)(2) Buildings with More Than One Rapid Shutdown Type. Buildings with both types of rapid shutdown, a detailed plan view diagram of the roof shall be provided showing each different PV system and a dotted line around areas that remain energized after the rapid shutdown switch is operated.

(3) Rapid Shutdown Switch. A rapid shutdown switch shall have a label located on or no more than 1 m (3 ft) from the switch that includes the following wording:

208

Minimum3/8” letter heightWhite letters on Red background

RAPID SHUTDOWN SWITCH FOR SOLAR PV SYSTEM

The labels required in (C)(1)(a) and (b) are plaques that can be placed on the switch.

The switch itself must have its own label as shown above.

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Article 110.21(B) provides guidance for lettering on labels and plaques

The PV array DC disconnect must label max system voltage and max circuit current on it. If a charge controller is present, its max output current must also be listed.

• The 2014 version also required operating current and operating voltage to be listed.

The AC disconnect must label the operating current and operating voltage of the interactive source “inverter(s)”.

Facilities with stand-alone systems must have a plaque on the exterior of the structure that shows the location of the system disconnecting means.

Facilities with interactive systems must have a plaque located at the service and the disconnecting locations that shows the location of all power source disconnecting means.

Buildings with rapid shutdown shall have a label within 3’ of the main service disconnect.

The rapid shutdown switch must be labeled:

RAPID SHUDOWN SWITCH FOR SOLAR PV SYSTEM

209

Review: PV System Labels and Plaques

210

1. Hand written labels or labels that do not meet the ANSI standard for size and the environment.

2. Multimodal systems don’t usually have the plaque for stand-alone PV system disconnect.

3. The plaque for rapid shutdown within 3’ of the service is usually missing because the 2014 code did not include this requirement.

4. Rapid shutdown switch label missing from AC disconnect when micro-inverters are used.

Most common violations

Addressing this potential violation.

1. Hand written labels should only be allowed on a battery system critical AC loads center.− Preprinted labels are available from several suppliers; HellermannTyton supplies the

industry with every PV label required and label printing products.

2. Multimodal system installers usually provide the interactive disconnect switch and label but not the stand-alone label denoting the location of that disconnect.

3. The 2017 requirement for the plaque within 3’ of the service should be enforced ASAP.

4. The 2014 NEC introduced the requirement for rapid shutdown but did not require the switch to be labeled if rapid shutdown occurred with micro-inverters or PV optimizers.

− This 2017 labeled switch requirement should also be enforced ASAP.

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690.59 Connection to Other Sources. PV systems connected to other sources shall be installed in accordance with Parts I and II of Article 705.

Interactive Utility Connection

211

Art. 705.12 Point of Connection

(A) Supply Side. An electric power production source shall be permitted to be connected to the supply side of the service disconnecting means as permitted in 230.82(6).

• The sum of the ratings of all overcurrent devices connected to power production sources shall not exceed the rating of the service.

e.g. Residential:

200a service at 240v = 48,000w x 80% = 38.4kW

15kVA transformer = 15,000w (15kW) Net metering limit is 10kW

Commercial: Line side connections are either under Georgia Powers tariff

or Qualifying facility. Net metering limit is 125% of peak usage.

Art 705.12 (A) Supply Side.

Art 230.82 Equipment Connected to the Supply Side of Service Disconnect.

(6) Solar photovoltaic systems, fuel cell systems, or interconnected electric power production sources.

Connecting to the supply side requires permission from the utility and must comply with the space requirements of the service box.

212

705.31 Location of Overcurrent Protection. For supply side connections in 705.12(A), the location of the OCD shall be within 3 m (10 ft) of the connected to the service.

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705.12 (B) Load Side. The output of an interconnected electric power source shall be permitted to be connected to the load side of the service disconnecting means of the other source(s) at any distribution equipment on the premises.

(1) Dedicated Overcurrent and Disconnect. Each source connection shall be made with dedicated overcurrent protection.

(2) Bus and Conductor Ampere Rating. Feeders, taps and busbars must be rated 125% of the power source (inverter) continuous current.

1) Feeders: b. An overcurrent device on the load side of the power source connection shall be rated not greater than the ampacity of the feeder.

The connection point is often the service lugs for the conductors.

2) Taps: The tap shall be rated no less than 125% of the inverter continuous current.

This refers to the inverter OCD.

A tab bonds directly to the conductor or lugs.

Customer Side Connection

213

705.12 (B) (2) Option 1

3)Busbars: One of the following four methods shall be used to determine the ratings of busbars in panelboards.

a) The sum of 125 percent of the inverter(s) output circuit current and the rating of the OCD protecting the busbar shall not exceed the ampacity of the busbar.

This is when the inverter OCD is placed anywhere along the busbar without regard to the location of the main OCD.

e.g. 200a busbar with 200a main OCD = zero margin for the inverter OCD

200a busbar with 150a main OCD = 50a margin for the inverter OCD

Customer Side Connection

214

PV Disconnect

Main AC Panel

200a bus

UtilityMeter

Disconnect

PV Utility Disconnect

DC Breaker & GFDI

AC Output

PV Array

1234kWH

+

-

15050

50a limit

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3) Busbars

(b) Where two sources, one a utility and the other an inverter, are located at opposite ends of a busbar that contains loads (branch circuit breakers), the sum of the ampere ratings of overcurrent devices supplying power to a busbar (main OCD + inverter OCD(s) shall not exceed 120 percent of the rating of the busbar rating.

• A permanent warning label shall be applied to the distribution equipment adjacent to the inverter back-fed breaker that displays the following or equivalent wording:

705.12 (D) (2) Option 2

215

e.g. 200a busbar with 200a main OCD = 40a margin for inverter OCD 200a x 120% = 240a - 200a OCD = 40a

2017 NEC: Replace “Inverter” with “Power Source”

Example 1 705.12(D)(2)(3)(b) Option 2

The busbar ampere rating can be oversized by 120% as long as the inverter OCD is placed at the opposite end of the busbar from the main OCD.

Example: 200 amp busbar with 200 amp main OCD

200 x 1.20 = 240 amps – 200 amp OCD = 40 amps PV OCD

The inverter OCD must be sized at 125% of the continuous current.

40 ÷ 1.25 = 32 amp inverter maximum continuous current.

32a x 240v = 7.68kW inverter

216

PV Combiner Disconnect

Main AC Panel

UtilityMeter

PV Utility Disconnect

Inverter & GFDI

AC Out

PV Array

DC in

+

-

40a limit

200

40

Tap allowed on exterior to full capacity.

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217

PV Disconnect

Main AC Panel

225a bus

UtilityMeter

Disconnect

PV Utility Disconnect

DC Breaker & GFDI

AC Output

PV Array

1234kWH

+

-

200

70

Example 2 705.12(D)(2)(3)(b) Option 2

The busbar rating is often greater than the main OCD when the main OCD is not located in the main AC panel.

Example: 225 amp busbar with 200 amp main OCD

225 x 1.20 = 270 amps – 200 amp OCD = 70 amps PV OCD

The inverter OCD must be sized at 125% of the continuous current.

70 ÷ 1.25 = 56 amp inverter maximum continuous current.

56a x 240v = 13.4kW inverter

Tap not allowed

70a limit

3) Busbars

(D) A connection at either end, but not both ends, of a center-fed panelboard in dwellings shall be permitted where the sum of 125 percent of the power source(s) output circuit current and the rating of the overcurrent device protecting the busbar does not exceed 120 percent of the current rating of the busbar.

705.12 (D) (2) Option 2 – center fed panels

218

PV Combiner Disconnect

Main AC Panel

UtilityMeter

PV Utility Disconnect

Inverter & GFDI

AC Out

PV Array

DC in

+

-

200

40

Make the same calculation and panel label used in (B) Option 2

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PV Disconnect

Main AC Panel

UtilityMeter

Disconnect

PV Utility Disconnect

DC Breaker & GFDI

AC Output

PV Array

1234kWH

+

-

Tap Area allowed to full capacity

OCD

Art. 705.12(D)(2)(1-2) Connecting to feeders and making taps

Using the 10 foot tap rule, the PV utility disconnect would need to be within 10’ of the tap and also be fused to protect the conductors beyond the 10’ tap area.

Tapping Into the Load Side

219

240.21 (B) Feeder Taps. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (5).

(1) Not over 10’ in lengthThe conductor taps must be adequately rated for the load and if they leave the tap container they must be rated no less than 1/10th of the main overcurrent device.

OCD

220

Polaris

Match service feeder size and equal tap

Listed taps with visible inspection capacity.

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705.12 (D)

(3) Markings. Equipment containing overcurrent devices in circuits supplying power to a busbar or conductor supplied from multiple sources shall be marked to indicate the presence of all sources.

This is simply labeling the load center with the inverter OCDs.

(4) Suitable for Backfeed. Breaker shall be rated for back-feed.

Most breakers are rated for back-feed. If it is not, it will be marked “Line and Load”.

(5) Fastening. Listed plug-in-type circuit breakers backfed from electric power sources that are listed and identified as interactive shall be permitted to omit the additional fastener normally required by 408.36(D) for such applications.

Generators and battery based inverter with outputs that are self-developed must have locking devices on the breakers;

Interactive inverter output is dead without utility connection (anti-islanding).

221

705.40 Loss of Primary Source. Upon loss of primary source, an electric power production source shall be automatically disconnected from all ungrounded conductors of the primary source and shall not be reconnected until the primary source is restored.

This the IEEE1547 anti-islanding protocol required of all interactive inverters.

705.100 Unbalanced Interconnections.

(A) The unbalanced load for multiple single phase inverters connected to 3-phase AC systems shall not exceed 3%.

Single phase inverters have three AC output options; 240v (L1, L2, Neutral) 208v (L1, L2, Neutral) and 277v (L1, Neutral).

• Any of these configurations will need to be in groups of three in order to maintain balanced conditions.

222

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223

Review Service Connections

With supply side connections the capacity of the PV system overcurrent devices cannot exceed the rating of the service.

For supply side connections the location of the PV system OCD must be within 10 ft of the service connection.

Load side connections allow four options to interconnect.

1. The busbar must be rated for the main OCD plus the OCD from the inverter.

2. The busbar may be exceeded by 120% as long as the inverter OCD is placed at the opposite end from the main OCD. (one or the other with a center fed busbar).

3. Full capacity of the busbar can be used if the branch circuit OCDs and the inverter OCDs do not exceed 100% of the busbar capacity.

4. A commercial engineered system is allowed to calculate with PV OCD fault studies.

Taps can be made with 100% of the feeder capacity if the tap is made between the main OCD in the load center and the OCD at the service location.

Breakers used to backfeed load centers must be rated for back feed.

Loss of utility power must shut the inverter down from selling into the grid. UL1741

224

1. Load side inverter OCD is oversized for the busbar of the main AC load center.

2. Load side inverter OCD is not placed at the opposite end of the load center busbar from the main OCD.

3. The label is not place next to the inverter OCD.

4. Improperly installed tap.

Most common violations

Addressing this potential violation.

1. This happens with contractors who are new to the industry and have not been trained.− Multiply the busbar rating x 120% - main OCD = max inverter OCD

2. As with #1, the installer would be new and untrained.

3. This is the most common violation; forgetting the label. This is for option #2.

4. There are UL listed taps that are questionable because it is difficult to verify the competency of the tap penetration.

− See the tap examples on the next slide.

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225

++ +

++ +

1234

kWH

J-box

PV array AC Panel

Driveway

MeterFront door

1

Labeling and Plaque Example, Interactive with micro-inverters

1. PV array AC disconnect(a) PV system disconnect label(b) AC disconnect label(c) Rapid shutdown Switch label(d) Plaque denoting location of rapid

shutdown switch(e) Power source disconnect directory

RAPID SHUTDOWN SWITCH FOR SOLAR PV SYSTEM

PV SYSTEM DISCONNECT

(a)

(b)

(c)

(d)

POWER SOURCE DIRECTORY

(e)

226

++ +

++ +

1234

kWH

J-box

PV array AC Panel

Driveway

Meter

1

Front door

Inverter

2 3

Labeling and Plaque Example, Interactive with string inverter

1. Photovoltaic power source label

2. PV array DC disconnect(a) PV system DC disconnect label(b) Possible Rapid shutdown switch label

3. PV array AC disconnect(a) PV system disconnect label(b) AC disconnect label(c) Rapid shutdown Switch label(d) Plaque denoting location of rapid

shutdown switch(e) Power source disconnect directory

RAPID SHUTDOWN SWITCH FOR SOLAR PV SYSTEM

PV SYSTEM DISCONNECT

(a)

(b)

(c)

(d)

POWER SOURCE DIRECTORY

(e)

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227

PV array

1++ + ++ +++ + ++ +

++ + ++ +++ + ++ +

++ + ++ +++ + ++ +

++ + ++ +++ + ++ +

++ + ++ +++ + ++ +

1234

kWH

Meter

2

Labeling and Plaque Example, Commercial string inverters

1. PV array DC disconnect label 2. PV array Stand-alone AC disconnect(a) PV system disconnect label(b) AC disconnect label(c) Rapid shutdown Switch label(d) Plaque denoting location of rapid

shutdown switch(e) Power source disconnect directory

1

1

1

12

2

2

2

AC

Pan

el

(a)(b)(c)

(d)

(e)

(a)(b)(c)

(a)(b)(c)

(a)(b)(c)

(a)(b)(c)

228

SOLAIRGENSchool of Solar technology

www.solairgen.com119 Highway 52 WestDahlonega, GA [email protected]

Review with question and answer

Battery systems slide 251

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229

Addendum 1:

Solar PV with Energy Storage Systems.

• These systems are gaining in momentum in many parts of the world and the U.S. Georgia will see a strong growth as well in the next few years.

• At this time most PV installations in Georgia are interactive without energy storage. This will most likely change slowly at first and the progressively more rapid.

− The reason for energy storage system growth is not because we have a poor electrical grid because we don’t.

− Interactive residential systems send most of the solar PV energy back into the grid each day and at a time when load demand is not high.

− Energy storage will make the grid stronger and make PV system energy more valuable to utilities.

Article 690 PV systems:

• Addresses batteries and energy storage; it also refers to other sections of the code that set minimum standards for installing battery systems and components.

Article 480 Storage Batteries:

• The article specifically addresses all batteries.

Article 706 Energy Storage Systems: New for systems operating over 60v DC

• This article consists mostly of what was previously in 690 with a few changes and additions plus it duplicates 480 but specifically to battery systems.

Article 710 Stand-Alone systems: New

• Covers other sections taken from 690 in previous NEC editions.

Article 712 Direct Current Micro-Grids: New

• This is the same as a multimodal systems. Micro-grids are potentially much larger and more complex than standard multimodal systems.

230

Code sections covering energy storage (2017 NEC)

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480.10 Battery Locations. (A) Ventilation. Provisions appropriate to the battery technology shall be made for

sufficient diffusion and ventilation of gases from the battery, to prevent the accumulation of an explosive mixture.

Informational Note No. 1: See NFPA 1-2015, Fire Code, Chapter 52, for ventilation considerations for specific battery chemistries.

Most sealed batteries do not gas and do not require this type of ventilation.

(C) Spaces About Battery Systems. For battery racks, there shall be a minimum clearance of 25 mm (1 in.) between a cell container and any wall or structure on the side not requiring access for maintenance.

(E) Egress. Door(s) intended for entrance to, and egress from, rooms designated as battery rooms shall open in the direction of egress (out) and shall be equipped with listed panic hardware.

Panic hardware is not typically required with residential systems.

(F) Piping in Battery Rooms. Gas piping is not permitted in dedicated battery rooms.

231

Requirements for All Battery Systems

690.55 Photovoltaic Power Systems Employing Energy Storage. Photovoltaic power systems employing energy storage shall also be marked with the maximum operating voltage, including any equalization voltage and the polarity of the grounded circuit conductor.

690.55 Photovoltaic Systems Connected to Energy Storage Systems. The PV system output circuit conductors shall be marked to indicate the polarity where connected to energy storage systems. Red for positive and black for negative

232

690.10 Stand-Alone Systems. The wiring system connected to a stand-alone system shall be installed in accordance with 710.15. See next slide

2014 label

MAXIMUM OPERATING VOLTGE _____

EQULIZATION VOLTAGE _____

POLARITY OF GROUNDED CONDUCTOR _____

GROUNDING (+, -, ungrounded) ______

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233

710.15(A) Supply Output. Power supplied by the inverter(s) to premises wiring systems shall be permitted to have less capacity than the calculated load.

− The capacity of the stand-alone supply shall be equal to or greater than the load posed by the largest single piece of electrical equipment connected to the system.

− Calculated general lighting loads shall not be considered as a single load.

This allows the inverter(s) to be rated less than a typical calculation would require and use load shed features. The minimum requirement is to have enough capacity to run the largest single load continuously.

(B) Sizing and Protection. The output circuit conductors from these inverters shall be sized based on the sum of their output ratings.

e.g. 2 - 8kW inverters with rated output of 240v, 33A require conductors and OCDs based on 66a continuous current.

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Article 710 Stand-Alone Systems

710.6 Equipment Approval. All equipment shall be listed or field labeled for the intended use.

All electrical equipment installed in the U.S. must be listed equipment. i.e. UL listed• Except for lead acid batteries

710.15 (E) Back-fed Circuit Breakers. Plug-in type back-fed circuit breakers connected to a stand-alone inverter output in either stand-alone or utility-interactive systems shall be secured in accordance with 408.36(D).

• Circuit breakers that are marked “line” and “load” shall not be backfed.

408.36 (D) Back-Fed Devices. Plug-in-type overcurrent protection devices that are backfed and used to terminate field-installed supply conductors shall be secured in place by an additional fastener that requires a means other than spring snap type pressure to hold the breaker in place when the cover is removed.

Overcurrent Breaker

Secured retainer

Locking devices for residential AC load centers are very limited.

Commercial load centers are usually bolted to the busbar.234

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Retaining Screw

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235

Outback Radian GSLA

Inverter manufacturer’s sell these load centers; they are designed for the application with bolt-in breakers.

408.36 (D) Back-Fed Devices, illustrated Bolt-in Load Centers

236

Direct Current System Grounding

250.167 Direct-Current Ground-Fault Detection.

(A) Ungrounded Systems. Ground-fault detection shall be required for ungrounded systems.

A ground fault detector on the battery side of a charge controller would serve both PV array ground fault and battery ground fault detection.

(B) Grounded Systems. Ground-fault detection shall be permitted for grounded systems.

(C) Marking. Direct-current systems shall be legibly marked to indicate the grounding type at the dc source or the first disconnecting means of the system. The marking shall be of sufficient durability to withstand the environment involved.

Ungrounded ESS will require ground fault detection on the DC battery system.

250.162(A) Two-Wire, Direct-Current Systems. A 2-wire, dc system supplying premises wiring and operating at greater than 60 volts to 300 volts shall be grounded.

250.164 Point of connection for DC systems

(B) On-Premises Source. Where the dc system source is located on the premises, a grounding connection shall be made at the following:

(2) The first system disconnection means or overcurrent device

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237

Review: Requirement for All Battery Systems

A spacing of 1” around individual battery cells is considered minimum.

Adequate ventilation is required on all batteries and batteries that gas out are required to have a method of removing those gases from the building.

Doors on dedicated battery rooms must open away from the room; some also require panic hardware.

Gas piping is not allowed in dedicated battery rooms.

Battery inverters suppling power to a load center must be rated for the largest load.

Stand-alone inverter output circuit breakers must be securely fastened to the load center.

The DC input current rating to a battery inverter is calculated at the lowest DC voltage.

This section covers all battery systems of all voltages.

The next section covers energy battery systems over 60v and is specific tot 2017 NEC.

• The 2014 NEC required most of what is in this section for all battery system voltages.

• Prior to the 2017 NEC the max voltage for residential battery systems was 50v (nominal).

• The maximum battery system voltage for 2017 NEC is 100v (maximum).

238

1. Residential energy storage PV systems regularly violate several of these areas. The ones of serious concern in this section are:

a) Adequate ventilation for all battery types and external ventilation for flooded lead-acid batteries (FLA).

b) Gas piping in the battery room

c) Breakers not being secured in the load center

2. Commercial energy storage systems are engineered; violations are rare.

Most common violations

Addressing this potential violation.

1. Residential energy storage systems that are pre-engineered as a package will have fewer violations. Self-built systems may have several.

a) Only FLA batteries pose a real threat; require the contractor to specify type on permit.b) The battery room is often shared with several other appliances. Water pipes and

HVAC ducts over the batteries is a violation. Gas pipes in the room are dangerous.c) With pre-engineered systems , the DC and AC overcurrent device centers will all be

bolt-in type. Self-built system may feed directly into the AC load center. This is where the unsecured breaker violation occurs.

2. Require the commercial contractor to submit detailed drawings.

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239

690 Part VIII. Energy Storage Systems (ESS) formerly “Storage Batteries”

690.71 General. An energy storage system connected to a PV system shall be installed in accordance with Article 706.

706.1 Scope. This article applies to all permanently installed energy storage systems (ESS) operating at over 50 volts ac or 60 volts dc that may be stand-alone or interactive.

706.30(A) Dwelling Units. An ESS for dwelling units shall not exceed 100 volts between conductors or to ground.

Exception: ESS that restrict access to live parts during routine maintenance may exceed 100v.

Article 706 Energy Storage Systems (operating at over 60v DC)

Equipment listed for use:

706.5 Equipment. Monitors, controls, switches, fuses, circuit breakers, power conversion systems, inverters and transformers, energy storage components, and other components of the energy storage system other than lead-acid batteries, shall be listed.

• Self-contained ESS shall be listed as a complete energy storage system.

Renewable energy storage batteries that are part of a larger battery bank are UL recognized instead of UL listed.

Battery system operating over 60 volts

240

Disconnect Requirements

480.7(A) Disconnecting Means. A disconnecting means shall be provided for all ungrounded conductors derived from a stationary battery system with a voltage over 60 volts dc.

The disconnect shall be readily accessible and located within sight of the battery system.

This was over 50v in the 2014 NEC.

706.7(A) ESS Disconnecting Means. A disconnecting means shall be provided for all ungrounded conductors derived from an ESS.

A disconnecting means shall be readily accessible and located within sight of the ESS.

See 706/7(E) for actual distance required from the ESS and the disconnect.

(B) Remote Actuation. Where controls to activate the disconnect are not located within sight of the system, the disconnect shall be lockable in the open position.

• The location of the controls shall be field marked on the disconnecting means.

This would be like a rapid shutdown device located on the exterior of the building.

• Not required but a good idea

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480

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241

706.7(B) Remote Actuation: Illustrated

Exterior switch for ESS disconnect.

Battery bank

Inverter

Battery bank

Inverter

Within sight of disconnect

Remote activated disconnect

5’

Placards are applied to each disconnect indicating the location of the other.

Disconnect

242

Energy Storage System rating

706.7(D) Notifications. The following must be marked on the battery disconnecting means.

(1) Nominal energy storage system (ESS) voltage

(2) Maximum available short-circuit current derived from the ESS

(3) The associated clearing time or arc duration based on the available short-circuit current from the ESS and associated overcurrent protective devices

(4) Date the calculation was performed

#3 above should be given by the battery manufacturer. Just multiply the Isc times the number of battery strings in parallel.

• An alternate method is to multiplying the 3 amp/hour rate by 20.

#4 is listed on the overcurrent device.

Polarity Marking

690.55 Photovoltaic Systems Connected to Energy Storage Systems. The PV system output circuit conductors shall be marked to indicate the polarity where connected to energy storage systems.

This refers to the standard of Red for + and Black for –

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243

Energy Storage System Disconnect

Nominal ESS voltage ______

Maximum short-circuit current ______

OCD arc clearing time ______

Date the calculation ______

706.7(D) Notifications: Illustrated

244

Disconnect Requirements

706.7(E) Partitions and Distance. Where energy storage system input and output terminals are more than 1.5 m (5 ft) from connected equipment, or where the circuits from these terminals pass through a wall or partition, they shall comply with the following:

(1) Fused or unfused disconnecting means shall be provided at the energy storage system end of the circuit.

(2) If the disconnect in (1) above is not within site of the equipment, a second disconnect must be installed at the equipment location.

(3) Where fused disconnects are used, the line of the terminals are toward the energy storage system.

(4) If the above disconnect is located within the battery vault with vented gasses the disconnect must be listed for hazardous locations.

(5) If two disconnects are required as indicated in (1) and (2) above, a placard must be placed at both locations indicating the location of the other disconnect.

This is required for all equipment connected directly to the ESS.

• A single disconnect to a DC equipment box would suffice.

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245

706.7(E) Partitions and Distance. Illustrated

More than 5’ and not within site of the disconnect

Disconnect

Battery bank

Inverter

Within sight of disconnect

Battery bank

Inverter

Within sight of disconnect

Additional disconnect required here

5’

Room partition

Placards are applied to each disconnect indicating the location of the other.

Disconnect

246

Connection to other energy sources

706.8 Connection to Other Energy Sources. Connection to other energy sources shall comply with the requirements of 705.12.

In short this article states that interactive systems with energy storage must follow the same requirements as interactive systems without energy storage.

The interactive connection from this inverter must comply with 705.12

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Directory

This code section is a duplicate of 705.10 Directory

247

If the PV system AC disconnect is located next to the service equipment location, the label on the disconnect is sufficient.

The directory can be in writing instead of a drawing.

• Using both is a better form of communication.

706.11 Directory. A permanent plaque or directory denoting the location of all electric power sources disconnecting means on or in the premises shall be installed at each service equipment location and at the disconnect(s) for each electric power production source capable of being interconnected. • The marking shall comply with 110.21(B).

This a close duplicate of 690.56(A) with the blue highlighted exceptions

706.11(B) Facilities with Stand-Alone Systems. Any structure or building with a photovoltaic power system that is not connected to a utility service source and is a stand-alone system shall have a permanent plaque or directory installed on the exterior of the building or structure at a readily visible location acceptable to the authority having jurisdiction.

• The plaque or directory shall indicate the location of system disconnecting means and that the structure contains a stand-alone electrical power system.

• The marking shall comply with 110.21(B).

Readily visible indicates a location that is visible from the main approach to the facility. i.e. as you drive up

248

THIS STRUCTURE CONTAINS A STAND ALONE

ELECTRICAL PV SYSTEM

PV SYSTEM DISCONNECT IS LOCATED

________________

9.5 mm (3⁄8 in.)lettering

White letters on red background

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3/16/2017 249

Part III. Electrochemical Energy Storage Systems

706.30 ESSs that are comprised of sealed and non-sealed cells or batteries or systems that are not components within a listed product.

(A)Dwelling Units. An ESS for dwelling units shall not exceed 100 volts between conductors or to ground.

(B) Disconnection of Series Battery Circuits. Battery circuits subject to field servicing and exceeding 240 volts nominal between conductors or to ground, shall have provisions to disconnect the strings into segments not exceeding 240 volts (nominal) for maintenance.

• Non–load-break bolted or plug-in disconnects shall be permitted.

(C) Storage System Maintenance Disconnecting Means. ESS exceeding 100 volts between conductors or to ground shall have a disconnecting means, accessible only to qualified persons, that disconnects ungrounded and grounded circuit conductor(s) in the electrical storage system for maintenance.

• A non–load-break-rated disconnecting means shall be permitted to be used.

(D)Storage Systems of More Than 100 Volts. On ESS exceeding 100 volts shall be permitted to operate with ungrounded conductors.

• A ground-fault detector and indicator must installed to monitor for ground faults within the storage system.

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ng v

olta

ge

Art. 110.14 Electrical Connections. This article states that connectors must be identified for the specific use. Fine stranded cables require lugs specific to their size.

The lugs on the left are rated specific for fine stranded cables.

Fine strand cable lugs

Connector and Terminal Ratings for Battery Cables

Polaris Grey are rated for fine stranded cable.Polaris Black must be sized exact. 250

706.32 Battery Interconnections. Flexible cables, as identified in Article 400, in sizes 2/0 AWG and larger shall be permitted within the battery enclosure from battery terminals to a nearby junction box or DC load center.

• These cables shall be listed and identified as moisture resistant.

• Flexible, fine-stranded cables shall only be used with terminals, lugs, devices, or connectors in accordance with 110.14.

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251

Review: Battery Systems over 60 volts

Article 706 is dedicated to energy storage systems ESS operating over 60v.

The maximum ESS voltage for dwelling units is 100v formerly 50v in 2014 and earlier.

A disconnecting means is required for ESS operating over 60v formerly 50v.

Systems operating over 60v must be grounded unless they contain a ground fault device.

Systems 60v or less and over 100v may be ungrounded if they have ground fault detection.

A label is required on the ESS to identify nominal voltage, short circuit current, the clearing time of the OCD and the date the calculation was performed.

PV circuits must be marked with their polarity when connected to systems with ESS.

A disconnect and OCD must be placed within sight of and within 5’ of the ESS.

Disconnects must be placed within sight of the equipment being disconnected.

If two disconnects are placed between an ESS and a piece of equipment, a placard must be installed at each location indicating the location of the other.

Interactive battery inverters must follow the interconnection rules of 705.12

A directory must be installed showing the location of all interconnected power sources.

Stand-alone facilities must display a plaque showing the location of the disconnect means for the electrical power system.

252

Review: Battery Systems over 60 volts, cont.

The max current for ESS equipment is the nameplate rating of the equipment.

DC overcurrent device must be rated for DC, the voltage and current as well as the automatic interrupt capacity (AIC) of the equipment being protected.

ESS that use the interactive connection to divert excess PV energy away from the batteries and into the grid, must have a secondary method of protecting the batteries from overcharge in case the grid fails. The same is true if a DC diversion controller is used.

ESS DC operating over 240v must have disconnecting means that section it to 240v or less.

ESS DC operating over 100v may be ungrounded if they contain a ground fault device.

Fine stranded cables require connectors listed specific to their size, current and voltage.

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253

1. The disconnecting means may be further than 5’ from the battery bank.

2. Most residential battery banks are ungrounded and not protected by ground fault protection devices.

3. Battery bank labeling may be insufficient.

4. The directory at the meter denoting the location of the stand-alone disconnecting means is usually missing.

Most common violations

Addressing this potential violation.

1. Most new factory made battery containers provide the option of integrated disconnect and OCD. Otherwise the inverter is the first location of the disconnect/OCD.

• If the conductors are in metal conduit, this is not an issue; exposed or PVC would be.

2. Require the method of grounding and battery fault protection on the permit so it can be verified during inspection.

3. The label should have Battery nominal voltage, short circuit current and polarity marked on it at a minimum.

4. Labeling is usually a problem with PV system installations; this label is the most often omitted.

• Require a list of labels on the permit.

THIS STRUCTURE CONTAINS A STAND ALONE

ELECTRICAL PV SYSTEM

PV SYSTEM DISCONNECT IS LOCATED

________________

++ +

++ +

Front door

Main Load Panel

+ + + + + + + +

Inverter

(3)

(2)

254

RAPID SHUTDOWN SWITCH FOR SOLAR PV SYSTEM

PV SYSTEM DISCONNECT

(a)

(b) (c)

(a)

1. Photovoltaic power source label

2. PV array DC disconnect(a) PV system disconnect label(b) Rapid shutdown switch label(c) PV system DC disconnect label(d) Plaque for PV system disconnect

3. PV array Stand-alone AC disconnect(a) PV system disconnect label(b) Plaque for Stand-alone disconnect

4. Interactive AC disconnect(a) Interactive AC disconnect label

5. ESS voltage and Isc label

(1)

(5)Rapid shutdown

device

Labeling and Plaque Example, (DC Coupled) PV with Energy Storage

Critical Load PanelController

(a) UtilityMeter12

34kW

H

(5)

THIS STRUCTURE CONTAINS A STAND ALONE

ELECTRICAL PV SYSTEM

PV SYSTEM DISCONNECT IS LOCATED

________________

(b)

(d)

(a)

POWER SOURCE DIRECTORY

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Labeling and Plaque Example, (AC Coupled) PV with Energy Storage

UtilityMeter

++ +

++ +

1234

kWH

Rapid shutdown device

Front door

+ + + + + + + +

Interactive inverter

(5)

(2)

255

THIS STRUCTURE CONTAINS A STAND ALONE

ELECTRICAL PV SYSTEM

PV SYSTEM DISCONNECT IS LOCATED

________________

RAPID SHUTDOWN SWITCH FOR SOLAR PV SYSTEM

PV SYSTEM DISCONNECT

(a)

(b)

(c)

(b)

(d)

(a)

1. Photovoltaic power source label

2. PV array DC disconnect3. Interactive Inverter AC disconnect

(a) PV system disconnect label(b) Rapid shutdown switch label(c) PV system AC disconnect label(d) Plaque for Rapid shutdown

4. PV array Stand-alone AC disconnect(a) PV system disconnect label(b) Plaque for Stand-alone disconnect

5. Bimodal Interactive AC disconnect(a) Interactive AC disconnect label

6. ESS disconnect(a) Voltage and Isc label

(1)

(6) (4) (a)

Critical Load Panel

Inverter

Main Load Panel

(3)

(a)

POWER SOURCE DIRECTORY

256

SOLAIRGENSchool of Solar technology

www.solairgen.com119 Highway 52 WestDahlonega, GA [email protected]

Review with question and answer