1. i-Vu Open System
BACnet MS/TP Networks
Bus Wiring

2. BACnet MS/TP Networks
What will we cover?
We will cover Carrier’s 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

3. BACnet MS/TP Networks Planning & Working With BACnet MS/TP Networks
We will cover:
MS/TP Network Requirements
MS/TP Network Devices
Creating a simple BACnet MS/TP network

4. BACnet MS/TP Networks A note about BACnet network definitions
Some of the definitions you may know from the CCN world are somewhat different in the BACnet world. Also, certain MS/TP network terms have no CCN equivalent. 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 the primary and secondary bus does not exist in MS/TP networking A Node refers to an Addressable Controller A Physical Segment of an MS/TP network is a contiguous length of medium to which BACnet addressable controllers (nodes) are attached A Segment of an MS/TP network is one or more Physical Segments connected by repeaters

5. MS/TP Network Planning
BACnet MS/TP Networks
MS/TP Network Planning

6. BACnet MS/TP Networks Network Devices & Tools
i-Vu User Interfaces (i-Vu Open server, Field Assistant) Network devices (i-Vu Open routers and links) Zoning Controls (factory & field installed) Application Specific Controllers Programmable Controllers & Expanders Ancillary 485 boards

7. BACnet MS/TP Networks i-Vu Open Network Controller Requirements
Maximum of 750 Controllers (nodes) for an entire i-Vu Open System Maximum of 60 nodes per MS/TP Network A <2000 foot network can have 32 nodes (no repeaters required) A repeater (REP485) is required after every 31 devices, or after 2000 feet (a repeater does not count as node) Each node on the MS/TP network must have unique MS/TP MAC address
Network and System requirements for a BACnet MS/TP network.

8. BACnet MS/TP Networks MS/TP Network Design Guidelines
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 the guidelines below to optimize MS/TP network performance.
Baud Rate
Maximum number of controllers per MS/TP network
76.8 kbps 60
38.4 kbps 30
19.2kbps/ 9600 bps 15

9. BACnet MS/TP Networks MS/TP Segment Requirements
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
Explain that this is the segment requirements of a BACnet MS/TP network.

10. Communications Wiring
BACnet MS/TP Networks
Communications Wiring

11. BACnet MS/TP Networks Recommended wiring specs and vendors
Source: MS/TP Networking/Wiring Installation Guide

12. BACnet MS/TP Networks Description
Single twisted pair, low capacitance, CL2P, 22 AWG (7x30), TC foam FEP, plenum rated cable
Conductor
22 AWG (7x30) stranded copper (tin plated) in. (0.762 mm) O.D.
Insulation
Foamed FEP in. (0.381 mm) wall 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) in. ( mm) wall in. (4.445 mm) O.D.
Halar (E-CTFE) in. (0.254 mm) wall in. ( 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
These are the specs for our recommended cable. Alternate cables should closely match these requirements.

13. BACnet MS/TP Networks Communication Wiring Recommendations
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 :
Communication wire should not touch the cable’s foil shield, shield wire or metal surface other than the terminal block
Do not ground the shield to earth ground or to the controller’s power ground.

14. BACnet MS/TP Networks MS/TP Network Shielding Details + - shield
Shield is always connected at the controller/device

15. BACnet MS/TP Networks Sensor Wiring
RNET Network 115 kbps baud 500 ft max length 4 conductor, unshielded 18 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.

16. Daisy Chain Network Topology
BACnet MS/TP Networks
Daisy Chain Network Topology

17. BACnet MS/TP Networks Sample MS/TP Network Segment1 3 2
Physical Segment
Physical Segment
Physical Segment
A Typical MS/TP network
Note: This example shows a network segment consisting of 3 physical segments joined by two repeaters

18. Ancillary RS485 Network Hardware
BACnet MS/TP Networks
Ancillary RS485 Network Hardware

19. BACnet MS/TP Networks i-Vu Open Ancillary RS485 Network Hardware
Terminating Resistors P/N# TERM485 (26-pack) Terminating Boards P/N# BT485 (16-pack) Repeater P/N# REP485 Protection Board P/N# PROT485
Nodes

20. BACnet MS/TP Networks What Is A TERM485
The TERM485 is a 120 ohm, ½ watt resistor that is attached to the controller at the beginning and the end of each physical segment to terminate the physical segment per the BACnet spec.
The TERM485 is installed across the NET+ and NET- terminals on the end controllers on each physical segment.

21. BACnet MS/TP Networks What Is A BT485?
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
Purpose: The BT485 is a device that you attach to the controller at the beginning and the end of each physical segment to add bias and to terminate the physical segment

22. BACnet MS/TP Networks
What is the difference between a BT485 and a Terminating Resistor?
The BT485 provides network bias and termination, the terminating resistor only provides network 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.
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.

23. BACnet MS/TP Networks BT485 and Line Terminators – Application Notes
A MS/TP network segment should have either of the following in order or priority:
1. A BT485 at 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.

24. BACnet MS/TP Networks Application of a BT485 Terminator
i-Vu Open Router
REP485

25. BACnet MS/TP Networks What Is A PROT485?
The PROT485 has two replaceable .5 A fuses
Purpose: It is a surge suppressor, and guards against large electrical surges on the communications network. It does not count as a network node

26. BACnet MS/TP Networks PROT485 Installation and Wiring
Mount at each place where
communication bus enters or exits the building
Install at least one PROT485 within 250 feet of every controller
Use the same polarity throughout the network segment
Purpose: Protects against large electrical surges on the communications network

27. BACnet MS/TP Networks Grounding the PROT485 – Controller within 6 feet
Female spade connector:
3M Corporation P/N
FD C or equivalent
Chassis Ground
6 feet long
6 feet long
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

28. BACnet MS/TP Networks
Grounding the PROT485 – No controller within 6 feet of PROT485
6 feet long
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

29. BACnet MS/TP Networks Sample PROT485 Network
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

30. BACnet MS/TP Networks What Is A REP485?
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-directional isolated ports that can communicate at baud rates from 1200bps to 156kbps
A network of <2000 feet can have 32 nodes (no repeater required)
The REP485 is not addressable

31. BACnet MS/TP Networks Using A REP485 (cont)?
On a network longer than 2,000 feet, place a REP485 after 2,000 feet regardless of the number of controllers (Segment A) Each REP485 counts against the 32 nodes/segment rule (Segment B) On a network with more than 32 controllers, place a REP485 after 32 nodes regardless of the length of the network (Segment C)
2000 ft
Segment A 6 1 2 3 4 5 7 8 9
1200 ft
Segment B 30 29 28 3 2 1
600 ft
Segment C 1 2 3 30 31
Nodes

32. BACnet MS/TP Networks REP485 Hardware Detail Network B Network A
Female spade connector
3M Corporation P/N
FD C or equivalent
Connect Earth Ground terminal
with a piece of 12 AWG ( no longer 2 feet )
Power: 24Vac 6VA)
BT485
Network A
Network B
Power Jumper
LED’s
Power
Network A blink when receiving data
Network B blink when receiving data

33. BACnet MS/TP Networks REP485 Wiring Terminations
Connect Earth Ground terminal
with a piece of 12 AWG (2 feet maximum). Use spade connector: 3M Corporation P/N
FD C or equivalent
Power: 24Vac 6VA)

34. BACnet MS/TP Networks REP485 - Power Wiring
Place the power jumper in the OFF position
Remove 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 verify that the voltage is within the operation range of 21.6 – 26.4 Vac.
Connect the EARTH GRND terminal with 12 AWG wire (2 feet 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 you maintain the same polarity and use the power supply only for i-Vu Open controllers

35. BACnet MS/TP Networks REP485 - Communication Wiring
Connect the communications wiring to the REP485’s Network A and Network B connectors. Add BT485 to each side of the repeater Verify communication with the network by viewing module status reports (modstat) in i-Vu or Field Assistant for controllers beyond the REP485.

36. Hybrid Network Topology
BACnet MS/TP Networks
Hybrid Network Topology

37. BACnet MS/TP Networks Star Network Topology1 4 5 6 3
Physical Segment
Physical Segment 2
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 on physical segment #2.

38. BACnet MS/TP Networks Star Network Topology 1 2 5 3 6 7 8 4
Physical Segment
Physical Segment
Physical Segment 3
Physical Segment
Physical Segment
Note: This example shows a network segment consisting of 8 physical 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 center physical segments (#5, 6, 7), and the physical segment on the bottom (#8) are the branches of the Star.

39. BACnet MS/TP Networks Rules Governing Hybrid Network Layouts
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)

40. BACnet MS/TP Networks Summary
Made up of various MS/TP networks back-boned by an IP network Each i-Vu Open server USB based MS/TP Network can have a maximum of 60 nodes. Each MS/TP network is made up of segments. Maximum length of one segment is 2000 feet with 32 devices max per segment. An i-Vu Open router will increase the capacity of the system, allowing up to 60 more MS/TP nodes per router to be connected to the network. On any given MS/TP network, a message from any controller cannot pass through more than 4 repeaters in order to reach its destination.
1-31
controllers
controllers

41. BACnet MS/TP Networks MS/TP Best Networking Practices
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 segment requires end-of-line termination for proper operation of the network.

42. BACnet MS/TP Networks MS/TP Best Networking Practices
Avoid running communications wiring or sensor input wiring next to AC power wires or relay wires.
MS/TP networking cable is comprised of a single twisted pair of wires (NET+ and NET-) and a shield (Alternatives are listed in the installation guide)

43. BACnet MS/TP Networks
TroubleShooting Tips

44. BACnet MS/TP Networks Communications Issues related to wiring:
Is EOL termination (BT485 or TERM485) installed at BOTH ends of the physical segment?
Are repeaters installed as required?
If sharing power, is polarity maintained amongst all the controllers?
Is the shield grounded at one or both ends instead of being terminated at the controller?
If sharing the MS/TP network with 3rd party BACnet controllers, make sure that these controllers do not have EOL termination or biasing enabled unnecessarily (check literature or rep of 3rd party equipment).

45. BACnet MS/TP Networks Optimizing Performance
Follow the max controllers per segment based upon the selected baud rate.
Controllers should follow contiguous addressing starting at 1.
Configure the Max Master and Max Info Frames to suit the system (set within driver properties of controller)
Max Master – the highest addressed controller would have this set to his address
Max Info Frames – specifies how many requests a controller can make while he has the token. Defaults for i-Vu Open devices:
Routers are set to 50
Controllers are set to 10

46. Additional BACnet Reference Information
BACnet MS/TP Networks
Additional BACnet Reference Information

47. The BACnet specification is available from ASHRAE at www.ashrae.org
BACnet MS/TP Networks
MS/TP Networking/Wiring BACnet Installation Guide
The MS/TP Networking/Wiring BACnet Installation Guide can be found on HVACPartners
ASHRAE BACnet Specification
The BACnet specification is available from ASHRAE at

48. BACnet MS/TP Networks
Thank You!
Questions?