1392647207_mstp wiring web training 04292011

8/12/2019 1392647207_MSTP Wiring Web Training 04292011

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BACnet MS/TP Networks

What will we cover?

We will cover Carriers recommendations

for the configuration, setup, installation,start-up, and wiring for a BACnet MS/TP

network that will provide the best network

performance with i-Vu Open controllers

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We will cover:

MS/TP Network RequirementsMS/TP Network Devices

Creating a simple BACnet MS/TP network

Planning & Working With BACnet MS/TP

Networks


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Some of the definitions you may know from the CCN world are somewhat differentin the BACnet world. Also, certain MS/TP network terms have no CCNequivalent.

A CCN Network= an i-Vu Open System

This defines the entire system of controls

A CCN Bus= a MS/TP Network

A MS/TP Network is equivalent to a CCN Secondary Bus. The concept of theprimary and secondary bus does not exist in MS/TP networking

A Node refers to an Addressable Controller

A Physical Segmentof an MS/TP network is a contiguous length of medium towhich BACnet addressable controllers (nodes) are attached

A Segmentof an MS/TP network is one or more Physical Segments connected byrepeaters

A note about BACnet network definitions


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MS/TP Network Planning


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i-Vu User Interfaces (i-Vu Openserver, Field Assistant)

Network devices (i-Vu Open routersand links)

Zoning Controls (factory & fieldinstalled)

Application Specific Controllers

Programmable Controllers &Expanders

Ancillary 485 boards

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Network Devices & Tools



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Maximum of 750 Controllers (nodes)for an entire i-Vu Open System

Maximum of 60 nodes per MS/TPNetwork

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MS/TP is a token passing network, meaning each node on

the MS/TP network can communicate only when it has the

token. The time needed for the token to cycle through the

MS/TP network is dependent on many factors. Follow theguidelines below to optimize MS/TP network performance.

MS/TP Network Design Guidelines


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Baud Rate Maximum number of

controllers per MS/TPnetwork

76.8 kbps 60

38.4 kbps 30

19.2kbps/ 9600 bps 15


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Each physical segment must be no

longer than 2000 feet

Each physical segment must start and

end with an end of line resistor

Maximum segment length of 10,000 feet

(5 physical segments of 2,000 feet, 4

repeaters)

A surge suppression device (PROT485)should be installed for surge protection

at each place communications wire

enters or exits the building or within 250

feet of each controller


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MS/TP SegmentRequirements


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Communications Wiring


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Recommended wiring specs and vendors

Source: MS/TP Networking/Wiring Installation Guide


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Description Single twisted pair, low capacitance, CL2P, 22 AWG (7x30), TC

foam FEP, plenum rated cable

Conductor 22 AWG (7x30) stranded copper (tin plated) 0.030 in. (0.762 mm)

O.D.

Insulation Foamed FEP 0.015 in. (0.381 mm) wall 0.060 in. (1.524 mm) O.D.

Color code Black/white

Shielding Aluminum/Mylar shield with 24 AWG (7x32) TC drain wire

Jacket SmokeGard (SmokeGard PVC) 0.021 in. (0.5334 mm) wall 0.175 in.

(4.445 mm) O.D.

Halar (E-CTFE) 0.010 in. (0.254 mm) wall 0.144 in. (3.6576 mm)

O.D.DC resistance 5.2 Ohms/1000 feet (50 Ohms/km) nominal

Capacitance 12.5 pF/ft (41 pF/meter) nominal conductor to conductor

Characteristic

impedance

100 Ohms nominal


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The wires are connected correctly to the terminal blocks:White wire to NET+ (typically, terminal 1 on a controller)

Black wire to NET-(typically, terminal 2 on a controller)

Shield/ground wire to Shield(typically, terminal 3 on a

controller)NOTE :

1. Communication wire should not touch

the cables foil shield, shield wire or

metal surface other than the terminal

block

2. Do not ground the shield to earthground or to the controllers power

ground.

Communication Wiring Recommendations


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++

+

+

-

--

-

shield

shield

shield

shield

MS/TP Network Shielding Details


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Sensor Wiring


RNET Network

115 kbps baud

500 ft max length

4 conductor, unshielded18 AWG, CMP, Plenum

rated wire

Analog & Discrete Sensor

Distances < 100 ft: Single

twisted pair, CM, 22AWG,

Plenum rated wire

Distances > 100 ft-500 ft:

Single twisted shielded

pair, CM, 22AWG,

Plenum rated wire.

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Daisy Chain Network Topology


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Sample MS/TP Network Segment

Note: This example shows a network segmentconsisting of 3

physical segmentsjoined by two repeaters

1

3

2

Physical

Segment

Physical

Segment

Physical

Segment


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Ancillary RS485 NetworkHardware


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Terminating Resistors P/N# TERM485 (26-pack)

Terminating Boards P/N# BT485 (16-pack)

Repeater P/N# REP485

Protection Board P/N# PROT485

i-Vu Open Ancillary RS485 Network Hardware


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The TERM485is a 120 ohm, watt resistor that is

attached to the controller at the beginning and the end of

each physical segment to terminate the physical segmentper the BACnet spec.

The TERM485is installed across the NET+ and NET-

terminals on the end controllers on each physical

segment.

What Is A TERM485


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Purpose: The BT485 is a device that you attach to the

controller at the beginningand the endof each

physical segment to add bias and to terminate the

physical segment

Push the BT485 onto the

connector located near the

BACnet port on the controller

BT485 has no polarity

associated with it

Verify the LED turns on

What Is A BT485?


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What is Network Bias?

Network biasing drives the NET+ and NET-signal wires to a reference voltage (>200mV)

when no device is transmitting.

Network biasing promotes reliable communication on the MS/TP RS485 network.

There should be one biasing device attached at each end of a network segment.


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What is the difference between a BT485 and a Terminating Resistor?

The BT485 provides network bias and termination, the terminating resistor only providesnetwork termination

What is Network Termination?

Network Termination adds a fixed resistance across the network, improving

communications reliability by suppressing signal reflections and reducing signal

distortion.


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BT485 and Line Terminators Application Notes

A MS/TP network segment should have either of the following in order or priority:

1. A BT485at each end (unless the segment is less than 10 feet [3 meters] long) to add bias

and prevent signal distortions.

2. A 1/2 watt, 120 Ohm terminating resistor (Part# TERM485) at each end to prevent signal

distortions

NOTES

A network should always be installed with some kind of termination.

The USB Cable used with the i-Vu Open server does not support the BT485. It would therefore

require a 120 ohm terminating resistor if the server is at one end of the network.

If the network segment contains a third-party device that applies bias to the network, you must do

one of the following:Set the third-party device so that it does not apply bias

Replace BT485's with 120 Ohm terminators

If a third-party device has its own termination resistance and is located at one end of the network

segment, do not install a BT485 or 120 Ohm terminator at that end of the network segment.

To attach a 120 Ohm terminator to an i-Vu Open controller, remove the MS/TP bus connector then

attach the terminator across NET+ and NET

terminals. Reconnect MS/TP bus to controller.


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REP485 i-Vu Open Router

Application of a BT485 Terminator


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Purpose: It is a surge suppressor, and guards against large

electrical surges on the communications network. It does not

count as a network node

The PROT485 has two

replaceable .5 A fuses

What Is A PROT485?


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Purpose: Protects against large electrical surges on the

communications network

Mount at each place wherecommunication bus enters or

exits the building

Install at least one PROT485

within 250 feet of every

controller

Use the same polaritythroughout the network

segment

PROT485 Installation and Wiring


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Use 12 AWG grounding wire, no more that 6 feet long. If controller is within 6 feet of

the PROT485 (as shown above), connect one ground wire to the power ground of the

controller and another ground wire to earth ground. Connect grounding wires to the

PROT485 Earth Ground spade lugs with spade connectors

6 feet long 6 feet long

Female spade connector:3M Corporation P/N

FD114-250C or equivalent

Grounding the PROT485 Controller within 6 feet


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Chassis

Ground


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Use 12 AWG grounding wire (no more that 6 feet long. Connect single grounding wire

to the PROT485 Earth Ground connectors with female spade connector

6 feet long

Grounding the PROT485 No controller within 6

feet of PROT485


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It is recommended to mount a PROT485 at each place where communication

wire enters or exits the building, and to install at least one PROT485 within

250 feet of every controller

Sample PROT485 Network


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It is a physical layer repeater that can be used to extend the

capacity and/or length of an RS485 MS/TP network

It has two bi-directionalisolated ports that can communicate at

baud rates from 1200bps to 156kbps

A network of


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On a network longer than 2,000 feet, place a REP485after 2,000 feet

regardless of the number of controllers (Segment A)

Each REP485counts against the 32 nodes/segment rule (Segment B)

On a network with more than 32 controllers, place a REP485after 32 nodes

regardless of the length of the network (Segment C)

Using A REP485 (cont)?


31Nodes

1200 ft

1

2000 ft

600 ft

2 3 4 5 6 7 8 9

1232930 28

1 2 3 30 31

Segment A

Segment B

Segment C


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LEDs

1. Power

2. Network A blink when receiving data

3. Network B blink when receiving data

Female spade connector3M Corporation P/N


Connect Earth Ground terminal

with a piece of 12 AWG ( no longer 2 feet )

Power: 24Vac 6VA)

BT485

BT485

Network A Network B

Power Jumper

REP485 Hardware Detail


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Connect Earth Ground terminal

with a piece of 12 AWG (2 feet

maximum). Use spade

connector: 3M Corporation P/N


REP485 Wiring Terminations


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Power: 24Vac 6VA)


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Place the power jumper in the OFF positionRemove the screw connector from the 24V supply

terminals on the REP485

Connect 24 Volts to the screw terminal connector

Measure the voltage at the power input terminals to verifythat the voltage is within the operation range of 21.626.4 Vac.

Connect the EARTH GRND terminal with 12 AWG wire (2feet or less )

Insert screw terminal connector into REP485 device.Place the power jumper in the ON position.

Verify the POWER LED lights is on.

Note: i-Vu Open controllers can share a power supply as long as youmaintain the same polarity and use the power supply only for i-Vu

Open controllers

REP485 - Power Wiring


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Connect the communications wiring to the REP485s

Network A and Network B connectors.

Add BT485 to each side of the repeater

Verify communication with the network by viewing modulestatus reports (modstat) in i-Vu or Field Assistant for

controllers beyond the REP485.

REP485 - Communication Wiring


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Hybrid Network Topology


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Star Network Topology


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1

4

5

6

3

Physical

Segment

Physical

Segment

Note 1: This example shows a network segment consisting of 6

physical segments. #1, 2, and 3 form the main branch, and #4, 5, and

6 are connected in a Star topology, using repeaters to establish the

branches of the Star.

Note 2: There are no nodes onphysical segment #2.

2Phys

ical

Segm

ent


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2 1

5

6

7

4 8

Star Network Topology


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Note: This example shows a network segment consisting of 8physical segments

connected in a Hybrid topology, using 4 repeaters to establish the branches of

the Star, and 3 repeaters to establish the main branch. The top, side, and bottom

physical segments (#1 through 4) are part of the main network segment. The

three centerphysical segments (#5, 6, 7), and thephysical segment on the

bottom (#8) are the branches of the Star.

Physical

Segment

Physical

Segment

Physical

Segment

Physical

Segment

Physical

Segment

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A message from one controller to another controller may not pass through

more than 4 repeaters (same as in a daisy chain)

A branch in a Star network may not have more than 4 physical segments

joined by three repeaters, thus a maximum of 8,000 feet

A physical segment in a Star network must begin with a repeater

A physical segment in a Star network must be terminated at both ends

An MS/TP network using Star network topology is limited to no more than 60

nodes (same as a daisy chain MS/TP network)

Rules Governing Hybrid Network Layouts


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Made up of various MS/TP networks back-bonedby an IP network

Each i-Vu Open server USB based MS/TPNetwork can have a maximum of 60nodes.

Each MS/TP network is made up of segments.Maximum length of one segment is 2000 feetwith 32 devices max per segment.

An i-Vu Open router will increase the capacity ofthe system, allowing up to 60 more MS/TPnodes per router to be connected to thenetwork.

On any given MS/TP network, a message fromany controller cannot pass through more than4 repeaters in order to reach its destination.

1-31

control lers

32 - 60

control lers

Summary


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Use proper cable and the

following principles when

connecting a node to an MS/TP

network.

Connect the shields of the cables

together at each node.

End-of-line termination- each

MS/TP network physical segmentrequires end-of-line termination

for proper operation of the

network.

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MS/TP Best Networking Practices



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TroubleShooting Tips


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Communications Issues related to wiring:

1. Is EOL termination (BT485 or TERM485) installed at

BOTH ends of the physical segment?

2. Are repeaters installed as required?

3. If sharing power, is polarity maintained amongst all the

controllers?

4. Is the shield grounded at one or both ends instead of

being terminated at the controller?

5. If sharing the MS/TP network with 3rdparty BACnetcontrollers, make sure that these controllers do not have

EOL termination or biasing enabled unnecessarily

(check literature or rep of 3rdparty equipment).

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Optimizing Performance

1. Follow the max controllers per segment based upon the

selected baud rate.

2. Controllers should follow contiguous addressing starting

at 1.

3. Configure the Max Master and Max Info Frames to suit

the system (set within driver properties of controller)

a. Max Masterthe highest addressed controller

would have this set to his address

b. Max Info Framesspecifies how many requests acontroller can make while he has the token. Defaults

for i-Vu Open devices:

a. Routers are set to 50

b. Controllers are set to 10 45

C S/


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Additional BACnetReference Information

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BAC MS/TP N k


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MS/TP Networking/Wiring BACnet InstallationGuide

The MS/TP Networking/Wiring BACnet InstallationGuide can be found on HVACPartners

ASHRAE BACnet Specification

The BACnet specification is available from ASHRAEat www.ashrae.org


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BAC t MS/TP N t k


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Thank You!

Questions?

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