Download - Power Supplies for Electric Motor Driven Fire Pumps

Fire Pump Power Supplies

Applicable Codes and Intent

- by -

James S. Nasby

Columbia Engineering

Topics to be Covered Are: 1 - Applicable Standards 2 - Power Source(s) for Fire Pumps 3 - Continuity of Power to a Fire Pump 4 - Transformers in the Fire Pump Circuit 5 - Power Wiring to a Fire Pump 6 - Other Requirements 7 - Rules of Thumb (For Reference Only) 8 - Fault Current Considerations

Applicable StandardsNFPA 70, the NEC®Article 695 -and-NFPA 20 Fire Pump Power Supplies

NFPA-20 - Chapter 9 - Performance & Acceptance Testing of Power Sources NFPA-70 (NEC®) Section 695 & etc. Installation of Electrical Equipment NFPA-25 - Inspection, Testing, etc. - also - Local Codes - E.g. C.E.C. (Chicago Electrical

Code) Insurance Company Requirements (IRI, FM & etc.)

NFPA 20 – Standard for the Installation of Stationary Pumps for Fire Protection

Several requirements of Article 695, including power sources, are extracted from NFPA 20

*

* Note: The NEC TCC rejected updating extract text from NFPA-20-2007. Thus the 2008 NEC retained the wording from NFPA-20-2003. A task group is looking into this situation.

What is Covered by NEC Article 695

Electrical power sources Interconnecting circuits Switching and control equipment

dedicated to fire fire pump drivers. E.g.: Service Entrance Gear.

695.1(A)695.1(A)

Power Sources Control Circuits Control Equipment

Fire Pump

What Is Not Covered By Article 695 System Performance -- NFPA-20 E.g.

Fire Pump Controllers and Transfer Switches.

Maintenance -- NFPA-25 Acceptance testing -- NFPA-20 Routine (Periodic) Testing -- NFPA-25 Jockey pumps -- NEC Article 430 Alarm Systems -- NFPA-72

COVERED

695.1(B)695.1(B)

How Is Article 695 Applied?

Because it is located in Chapter 6, –Article 695 applies to special equipment – It amends the requirements of Chapters 1

- 4 in the NEC for fire pump installations Example:

–Article 695 amends Articles 240 and 430–Article 695 is NOT modified by Article 700

(Emergency Systems)

90.3 & 695.290.3 & 695.2

What Is the Intent . . . of Article 695 -and- NFPA-20

Fire Pump sources and components must be Reliable, and

Should the Fire Pump Be Called Upon to Function, It Is Considered Sacrificial

NFPA 20 and 695.3

2 - Power Source(s) for Electric Motor Drive Fire Pumps

General Philosophy Permitted power source(s) Individual power sources(s) Multiple power sources Power source(s) performance

Maximum Voltage Drops

General PhilosophyPower Sources for Electric Motor Driven Fire Pumps

Requirements focus on the continuous uninterrupted operation of the fire pump.

Electrical safety is considered a secondary objective.

Fire pump equipment is considered sacrificial.

As such, Equipment and Conductors may constitute a fire hazard.

Protection of the premise and occupants of paramount importance.

Permitted Types of Power Sources for Electric Motor Driven Fire Pumps

Individual Power SourceUtility Service On-Site Power Production Plant

Multiple (other) Power SourcesAbove twoStand-by Gen-setFeeder Sources(Campus like Complexes)

695.3695.3

Number of Reliable Electric Power Sources Required

Power to be supplied by a (one) reliable source

Or by at least two approved independent (other) sources.

-- however --

Where height of building is beyond pumping capacity of the fire department, an emergency or back-up power supply is mandatory.

-and- Additional Chicago Requirements

A Reliable Electric Power Source . . .

To consist of Electrical Service or Private Power Station - where -

Infrequent disruption from environmental or man-made conditions

Contains a separate service connection -or- connection to the supply side of the building’s service entrance disconnect means

Determination of reliability up to discretion of the AHJ (Authority Having Jurisdiction).

What Are Individual Power Source(s)?

1. Separate Service, or 2. Tap Ahead of the Premise (Plant or Building) Service Equipment - or - 3. On-Site Power Production

Facility (On-Site “24-7” Power Plant)

695.3(A)695.3(A)

Separate Service as an Individual Power Source.

Separate utility service dedicated to the fire pump

Permitted by Section 230.2 Shall comply with all applicable rules of Chapters 1-4, including Article 250.

Each Individual Power Source

Must be Located –

and Arranged to Minimize Possibility of Damage By Fire.

“…sufficiently remote…” 230.72(B)

And, both must have signs at both location. 230.2(E)

Separate Service From a Utility

Normal ServiceFire Pump

Service

SufficientlyRemote

Locations

Power Supply Arrangement

Power supply to pump is to be maintained when building normal power is disconnected.

Exception for feeder circuit serving as one source - disconnection of plant power to fire pumps permitted if alternate source is continually available

Tap Ahead of the Building Service

Equipment requirements are the same as for a separate service

Installed according to Part D of Article 230, service entrance conductors; e.g.: 230.82(4), 230.2(A)(1), 230.72(B),

Be capable of carrying the locked-rotor current (LRC) of the Fire Pump and all connected all equipment loads

695.3(A)(1) &695.3(A)(1) & 695.6(D)695.6(D)

On-site Power Production Facility

This is not a ordinary standby generator, but rather

A facility that produces its own power on a Continuous basis

Similar to separate service requirements

Located and protected to to minimize the risk of damage by fire

695.3(A)(2)695.3(A)(2)

Multiple Power Sources - When Needed

The Term “Reliable” Is a Decision for “The Authority Having Jurisdiction”.

“Reliable” Is Defined as “Capable of Being Relied On; Dependable, or Trustworthy”.

All Sources Must Be Approved by “The Authority Having Jurisdiction”.

ReliableDependable

Trustworthy

695.3(B)

Multiple Power Sources - NFPA 20

Governed by NFPA-20 Section: 6-2.3 Other Sources

Excerpted into NEC Article:695.3. Power Sources(s) for Electric

Motor-Driven Fire Pumps

Multiple Power Sources -- Other Electric Power Sources

Where a Reliable Power Source is NOT available, redundant (Multiple) supplies are to be provided as follows:Another Service or Private Power StationOn-site standby GeneratorCombination of Feeders from Two

Separate Utility SourcesCombination of One or More Feeders

and an Onsite GeneratorDiesel Engine driven Fire PumpSteam Turbine driven Fire Pump

Examples of Multiple Power Sources

1) Dual Utility Service 2) Utility Service plus On-Site Gen-

Set 3) Combination of Feeders from

separate Services ** 4) Combination of Feeder and On-

site standby generator **

** Only allowed on multi-building, campus style complexes.

Examples of Multiple Power Sources NFPA-20 Section 9.2, Power Sources

(1) Combination of Services and/or On-site Power Facilities.

Fire Pump Controller

Service #1 Service #2

MFire Pump

Motor


(2) Combination of Service or OPF and On-site standby generator.

M

Service On-site standby Generator

G



(3) Combination of Feeders from separate Services.

Only allowed on multi-building, campus style complexes.

Service #2Service #1

High Voltage

Substation

Feeders


M


(4) Combination of Feeder and On-site standby generator.

Only allowed on multi-building, campus style complexes.

On-site Standby Generator

Service

FeedersFire Pump Controller

M

High Voltage Substation

G

Examples of Multiple Power Sources NFPA-20 9.2, Power Sources (Tap Ahead . . .)

6.3.2.1 The fire pump power supply shall not be disconnected when plant power is disconnected.

The exception permits this only for multi-building, campus-style complexes that automatically ensure alternate power is still available.

Service

FeedersFire Pump Controller

M

Plant Power Disconnect

Multiple Power Sources -On-site Generator

Generators to be of sufficient capacity to allow normal starting and running of the motor(s) driving the fire pump(s) while supplying all other simultaneously operated load(s).

Where protective devices are installed, they must allow instantaneous pickup of full pump room load. E.g. Across-the-Line Starting of all pumps.

Transfer of power to take place in the pump room Meet Both Voltage Drop Requirements (15% &

5%)

Multiple Power Sources -- On-site Generator

Generator to meet requirements for Level 1, Type 10, Class X system as defined by NFPA 110, Standard for Emergency and Standby Power SystemsLevel 1 - Critical to life safety. Type 10 - Power available within 10 secondsClass X - Sufficient fuel to run for a period of “X”

hours

Sufficient fuel supply so generator can operate for eight hours at 100% capacity of the pump and other demands (Class “8”).

Multiple Power Sources -- Transfer of Power

Transfer Must Occur within the Pump Room

Arrangement I -- Combination Controller & Transfer Switch per NFPA-20 Section 9.8.2.1 -or- Arrangement II -- Separate Field Wired Controller &

Transfer Switch per NFPA-20 Section 9.8.2.1

Arrangement I Controller - Xfer. Switch

Combination

A “Combination Fire Pump Controller and Power Transfer Switch” unit must . . .

Be Listed as a coordinated designed and factory assembled and wired complete unit

Need have only Normal Side Breaker unless the Emergency Source is a Utility (need to specify Emergency Side Breaker when needed).

Will already meet all requirements of NFPA-20, Section 10.8

Arrangement II Transfer Switch Ahead of

Controller

A transfer switch ahead of a fire pump must . . .

Be a Listed “Fire Pump Power Transfer Switch”

Be Listed and Rated for the Available Fault Current. NFPA 20, 9.1.2.2

Be Protected by Listed Service Equipment Meet all requirements of NFPA-20, Sections

10.8.1, 10.8.2.2 & 10.8.3

Approximately 31 clauses including interconnections and WIC Short Circuit Coordination. See Nasby Application Notes

Multiple Power Sources - Summary

Where Reliable Power Cannot Be Obtained from a Single Source,

Two or More Sources Shall Be Required.

The Sources to Select from are Limited to Those Covered in Section 695.3.

Multiple Sources are Required Where Building Height Exceeds Fire Department Pumping Capacity.

695.3(B)695.3(B)

Power Supply Performance – Any and All Sources

Max. Voltage Drop Requirements

15% Under “Normal” Starting Conditions E.g.: Reduced Voltage Starting on Reduced Voltage (Reduced Current) Starting Controllers

5% Under 115% Full Load Running Conditions

Maximum Allowed Voltages Drops – Motor Starting

During Normal Starting Conditions, a 15% Maximum Voltage Drop at Controller Inlet Terminals.

“Normal” motor starting conditions includes Reduced In-rush Starting, if provided.

Exception for Emergency Manual Mechanical (A-T-L)starting

This is to Assure Adequate Control Power. VD ( 3 Phase ) = 2 x K x L x I

Circular MilsX 0.866

695.7695.7

Maximum Allowed Voltages Drops – Motor Running

During Motor Running at 115% of Motor FLA, a 5% Maximum Voltage Drop at the Motor Terminals.

This is to Prevent Motor Overheating.

See NEC Chapter 9, Table 9 for cable A.C. Impedances (Resistance & Reactance).

See NEMA ICS-14 for example of voltage drop calculations.

Available at: http://www.nema.org/standards

695.7695.7

3 - Continuity of Power

Goal – Minimize risk of inadvertent disconnection from supply.

Connect fire pump directly to electric supply

Limit number of disconnecting means Supervision - Monitor Fire Pump

Power actually present Transfer Switch ahead of Controller

695.4695.4

Physical Protection of Electric Power Supplies

Power sources supplied by a service or generator to be located and arranged to minimize the possibility of damage by fire from within the premises and exposing hazards.

If power supplied solely by a private power station, it is to be protected as above.

Private Power Station may be given consideration as an acceptable supply where located in a separate power house or cut off from main buildings

Physical Protection of Power Supplies (Cont.)

Multiple power sources to be arranged so a fire at one source will not cause an interruption at the other source.

Supply conductors to be dedicated and protected to resist possible damage by fire, structural failure, or operational accident

Continuity of Power

Power supply to be directly connected to the fire pump controller,

-- or --

A single supervised disconnecting means and associated overcurrent protective device permitted between the power supply and fire pump controller, power transfer switch or combination controller/transfer switch

Methods of Achieving Continuity

Direct Connection

Supervised Connection (Upstream OCP)

M

FIRE PUMP CONTROLLER

XSERVICE POINT

FIRE PUMP


FIRE PUMP

XSERVICE POINT

SERVICE DISCONNECTING

MEANS

M

695.4

Direct Connection of Supply Conductors

The simplest is a direct connection

Benefit: Limited risk of inadvertent

disconnection

M


XSERVICE POINT

FIRE PUMP

695.4(A)695.4(A)

Supervised (Indirect) Connection

Indirect (Supervised) Connection is permitted, but . . .

Considered somewhat less reliable, and

Is more complex (approx. 8 clauses)

Basically, this allows a disconnect ahead of the fire pump

Supervised (Indirect) Connection – cont’d

A Single Disconnecting Means and Overcurrent Protection are permitted ahead of the Fire Pump Controller, only if all of the following conditions are met (next four slides):


FIRE PUMP

XSERVICE POINT


MEANS*

M

695.4(B)695.4(B)

*Service Entrance Rated (Listed) Fusible Disconnect or Enclosed Circuit Breaker

The Disconnecting Means . . . Identified and Marked “Suitable for Use

As Service Equipment” (U.L. Listed) Lockable in the “Closed” (ON) position Located sufficiently remote from other

disconnecting means that inadvertent contemporaneous operation would be unlikely

Marked appropriately (Marked “Fire Pump Disconnecting

Means”) Disconnecting means supervised in the

closed position

The Overcurrent Protection . . . The Overcurrent Protection Is Set to carry

indefinitely the sum of the locked rotor current of the fire pump, jockey pump motors and full-load current of associated fire pump equipment

Exception: Additional devices for campus style feeder sources - to comply with NFPA 70 §695

Note: Except for Limited Service units, the Controller’s overcurrent protection is set to: - Never trip below 300% of motor FLA -and- - Locked rotor tripping time set between 8 seconds and 20 seconds

Means of Supervision of Disconnect

a. Fire Alarm Connection to a Central Station, Proprietary, or Remote Station Signal Device.

b. Local Signaling Service that Will Cause an Audible Signal at a Constantly Attended Point.

c. Locking the Disconnect “Closed”d. Sealing in Closed Position with Weekly

Inspections where the Disconnecting Means is within a Fenced Enclosure or in buildings under “control of the owner” (Locked).

Additional Disconnect Requirements

A Key Is Placed at the Fire Pump Controller, if the Disconnecting Means Is Locked, and

A Placard is Installed on the Disconnecting Means, and

An Additional Placard Is Installed at the Fire Pump Controller, and

The Disconnecting Means Is Supervised in the Closed (“ON”) Position


FIRE PUMP

XSERVICE POINT


MEANS

M

695.4(B)695.4(B)

4 - Transformers for Fire Pump Circuits

A Transformer is Permitted Where . . .

13.2 kV 3 PHASE

DELTA

480 / 277 V 3 PHASE 4-WIRE

WYE

695.5695.5

Transformers for Fire Pump Circuits

Service at Other than Utilization Voltage

Where “Service” is Above 600 Volts either a:

Listed Medium Voltage Fire Pump Controller(s) and Motor(s) if below 7.2 kV -or-

A Transformer(s) is allowed per NFPA-20 6.3.2.2.5 if it complies with 6.3.2.2.2

(Supervised Connection) and NEC Article 695.5 (Transformers).

Power

Supply

Arrangement

'A' & 'B'

for

Normal Source

Note: Transformer in Arrangement 'B' is optional

Transformers for Fire Pump Circuits

A Transformer is Permitted Where the Supply Voltage Is Different from the Fire Pump and Controller Requirements

It is Dedicated to Fire Pump and Associated Equipment or

Except that Transformers on Multi-Building Complexes are Permitted to Supply Other Loads

695.5695.5

MM

JockeyPump Disconnect, Overcurrent Protection, and Motor Controller

Jockey PumpFire Pump

Listed Fire Pump Controller

Primary Overcurrent Protection Only

Dedicated Transformer

Jockey Pump Tap Conductors

Secondary Conductors, Overcurrent Protection NOT Permitted

Transformer Dedicated to Fire Pump

695.5695.5

Transformer Sizing Minimum Sizing Shall Be at Least 125%* of

the Sum of: The Full Load of the Fire Pump Motor(s),

Plus The Full Load of the Jockey Pump Motor(s) (if applicable), Plus The Full Load of Any Associated Equipment (if applicable).

695.5(A)695.5(A)

Note: *125% is almost always too small to meet the two voltage drop requirements.

Transformer Overcurrent Protection

Secondary Side Overcurrent Protection (OCP) is Not Permitted.

Line side protection only

695.5(B)

Transformer Overcurrent Protection

The Minimum Selection and Setting of the Primary OCP Shall Be Large Enough to Carry Indefinitely the Equivalent Secondary Currents of the Following:

The Locked-Rotor (600%) Current of the Fire Pump Motor(s), Plus

The Locked-Rotor (600%) Current of the Jockey Pump Motor(s) (if applicable), Plus

The Full Load (100%) Current(s) of Any Associated Equipment (if applicable).

695.5(B)

Power Supply Component andWiring -- Code References

Direct Connection

Indirect Connection

(Service Entrance Disconnect and OCP upstream of the Fire Pump)

Transformer Connection

5 - Power Wiring

Service Conductors (Electric Utility) Supply Conductors (On-site Power

Production) Feeder Conductors connected to:

1. On-site standby generator 2. Supervised disconnecting means

Feeder Conductors for multi-building (campus style) complexes

Power Wiring (The Supply Conductors) Shall Be . . . Installed As Service Entrance Conductors,

and Physically Routed Outside the Building, or Permitted to Be Routed Through Building if

Installed Under, Or Enclosed Within, Not Less Than 2 Inches of Concrete (See Section 230.6 ).

Multi-Building Complex Feeder Conductors (Normal Supply) on the Load Side of Disconnecting Means and Overcurrent Protection Shall Comply With These Requirements

695.6695.6

Power Wiring-Circuit Conductors on Load Side of Disconnect and

Overcurrent Protection-Within the Building

Shall be protected to resist damage from fire, structural damage or operational failure and

Encased in not less than 2 inches of concrete, or

Installed within 2-hour* fire resistance rated enclosed construction dedicated to the fire pump circuit(s), or

Installed within listed electrical circuit protective systems having a minimum 2-hour* fire resistance rating.

Remember that these conductors are sacrificial.

* Was 1-Hour

Listed Electrical Circuit Protective Systems

Permitted to Be Routed Through Building if Installed in Listed Electrical Circuit Protective Systems With A Minimum of 2-Hour Fire Resistance.

Note: Not allowed in all jurisdictions for Service.

Mineral Insulated Cable

695.6(B)695.6(B)

Electrical Circuit Protective System May Consist of a . . .

2-inch Rigid Conduit with 250 kcmil XHHW, Copper Conductors Installed with a U.L. Listed (Classified) Overall Covering of a 2-Hour* Fire Resistance Blanket System, or

* Was 1-Hour Listed (Classified) Fire-Resistive

Mineral Insulated (MI) Cable Systems,

- and -

Electrical Circuit Protective System May Consist of a . . .

Other Systems and Configurations Are also Listed (Classified).

See “Fire Tests for Electrical Circuit Protective Systems”, UL Subject 1724-1991 for Exact Information.

See U.L. CCN (Guide) FHIT. Details at: “http://www.ul.com” Online

Certifications Directory

Section 695.6(B) Exception - Electric and Fire Pump Rooms

Supply Conductors Are Exempt from Fire-Resistance Ratings Only:

In the Electrical Switchgear Room, and In the Fire Pump Room.

Electric Room Fire Pump Room

695.6(B) Exc.695.6(B) Exc.

Wiring Methods for Power Circuits – Within the Pump Room

Rigid Metal Conduit Intermediate Metal Conduit Liquidtight Flexible Metal Conduit Liquidtight Flexible Nonmetallic Conduit

(LFNC-B) Listed MC Cable (w/ Impervious

Covering) Mineral Insulated Cable (MI) Wiring Method for Control Circuits Are

Essentially the Same.

695.6(E)695.6(E)

Fire Pump Controller Controller May Not Be Used As a

Junction Box for Other Circuits. Jockey Pump Connections Not Allowed

to Be Made in Fire Pump Controller.Note: Either Fire Pump Circuit or Local

Branch Power may be used for the Jockey Pump.

695.6(F)695.6(F)

Fire Pump Controller Jockey Pump Controller and Separate Junction Box

695.6(F)695.6(F)

Junction Box Required when…

9.3.7.1* Where single conductors (individual conductors) are used, they shall be terminated in a separate junction box. Single conductors (individual conductors) shall not enter the fire pump enclosure separately.

These are typically MI cables with solid wire. - Splices to Stranded Wire Required (Breaker Lugs

are Rated only for Stranded Wire. - Separate cables will create a magnetically

induced (eddy) current in ferrus metal (steel). This can easily heat #14 gage steel to red hot.

- A nonferrus (Aluminum) junction box or plate is used since no current is generated.

- Controllers were being hacked up, which violates both their NEMA Enclosure Type rating and the WIC rating.

Junction Box Required when…

9.3.7.2* Where required by the manufacturer of a listed electrical circuit protective system or by NFPA70, National Electrical Code, or by the listing, the raceway between a junction box and the fire pump controller shall be sealed at the junction box end as required and in accordance with the instructions of the manufacturer.

This is usually for type MC or Type RHW Listed High Temperature Wire. These give off flamable smoke when routed thru the fire zone. The controller is an arcing (sparking) device (open contactors) and requires a junction box and seal to keep smoke from entering the controller thru the incoming conduit.

Fine Stranded Wire (Cable) Warning Some Wire and Cable Mfr’s are Making

Multiple Rated Cable, Such as: AWM, MTW & TEW, among other ratings. TEW is a fine stranded type of cable and AWM may be.

Circuit Breakers (Isolating Switch) Incoming Lugs are Neither Tested nor Rated for Fine Strand Wire

Ditto for Contactor (Outgoing) Lugs This applies to both Field and Factory

WiringNote: The wire types listed in NEC Tables

310.16 & 310.17 are usually Not fine stranded. E.g.: Suitable.

6 - Other Requirements

External Control Circuits No Sensors or Remote-Control Devices Control Wiring Multiple Pumps - Sequential Starting

External Fire Pump Control Circuits (Remote Start, Deluge Valve Start, etc.)

Arranged So That Failure of Any External Control Circuit Shall Not Prevent the Operation of The Pump(s) by Other Means.

Circuit Failures Such As Opens, Shorts, Grounds, or Loss of Power Are Permitted to Cause the Pump to Run, but

These Failures Cannot Prevent the Fire Pump from Running.

695.14(A)695.14(A)

Prohibited Sensors & Control Devices Undervoltage, Phase Loss, Frequency

Sensitive, or Other Sensors Are Not Permitted, Except…

Motor Single Phase Start Attempt Protection Is Permitted.Exception to 9.4.5.6 allows controllers that prevent 3-phase motor from starting under single phase conditions, but that do not disconnect a running motor

Remote Devices in the Control Circuit Are Not Permitted if They Prevent the Automatic Operation of the Transfer Switch.

695.14(b) & (c)695.14(b) & (c)

Wiring Methods for Control Circuits Rigid Metal Conduit (Threaded) Intermediate Metal Conduit (also

Threaded) Liquidtight Flexible Metal Conduit Listed MC Cable (w/ Impervious Covering) Mineral Insulated Cable (MI) There Are No Exceptions to These Wiring

Methods Not Allowed:

Flexible Metal Conduit (like BX)Thin Wall ConduitRomex or Any Other Bare Cable

695.14(E)695.14(E)

Specify Sequencing of Multiple Pumps when . . .

Automatic sequencing of pumps required in accordance with 9.6.3 (and required by 10.5.2.5).

Note: This eases the starting electrical load. Automatic sequencing of fire pumps

needed for pumps in parallel or in seriesAny pump supplying suction to another pump starts

before it (High Zone Delayed Start) -or- if water requirements call for more than one pumping unit to operate.

Pumps to start at intervals of 5 to 10 seconds.Failure of any one pump doesn’t prevent others

from starting.

7 – Rough Rules of Thumb Transformer or Gen-Set Sizing – 125%

almost never enough

Full Voltage (A-T-L) StartingOften needs 300% to 500% Sizing

Reduced Inrush StartingOften needs 250% to 400% Sizing

Depending on: Device Impedance and Voltage Drops of:

Transformer Source and Primary Wiring Run

-and- Wiring Run to Controller

8 - Fault Current Considerations Controller Short Circuit (WIC) Rating Must

exceed the “Available Short Circuit Current”

Ditto for Arrangement II Upstream Xfer SwitchThis almost always requires upsizing the Xfer

Switch to coordinate with the 600% (Minimum) upstream OCP (Over Current Protection)

Controller and Xfer Switch must be marked with the Short Circuit Rating and be “Suitable” for same.

10.1.2.210.1.2.2

What’s Wrong with This Picture?Notes:

1) Most E.F.P.C.s use “Gapless” “Secondary Arresters”

2) Some have limited self protection (bare wire links)

3) All gapless MOV arresters are subject to thermal run-away due to follow on currents.

4) Three phase arcs are NOT self extinguishing.

What’s Wrong with These Pictures?

Severe Lightning Strike takes out Utility Arrester in a Very Lightning Prone Area. Also Damages Xfmr

(Pot), Requiring Replacement; but, No Damage to Controller!

Some Time Later on a Car Hits Another Pole Down the Alley and Causes a High Line (2.3 Kv) Cross to the Neutral which Takes Out Most of the Pump Room Loads and Damages one of the 3 CPTs in Controller.

Back in Service in Minutes

Technician Cut the Two Primary CPT Wires and Put the Controller

Back in Service

In only Minutes!

(The Chassis was Replaced Later.)

Smoked the Center CPT

2,300 Vac on 480 Vac Primary

Questions ?

Download - Power Supplies for Electric Motor Driven Fire Pumps

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