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Common tests, results, and potential root causes of issues on BACnet MSTP bus.

 

1. Check Resistance (Set to Ohms)

Common Issues

 O

 

Shield

Normal Reading

0 Ohms

Greater than 3 Ohms: Shield is not grounded.

 O

 

Earth Ground

Less than 3 Ohms when ground is removed: You are grounded in more than one place. Find the extra ground and eliminate it. Only ground once on your network.

 


2. Check DC Voltage | A- and B+ (Set to DC)

Common Issues

 O

A-

Normal Reading

200 MV or 0.2 VDC

Less than 200 MV: A- and B+ are shorted on network.

 O

 

B+

Greater than 500 MV: Either 1) A- and B+ are not connected on one side of the network; or 2) an end of line (EOL) switch is not turned on.

 


3. Check DC Voltage | B+ and Earth GND (Set to DC)

Common Issues

 O

Earth Ground

Normal Reading 2.0 - 2.5 VDC

Less than 700 MV: B+ is shorted to the shield, potentially by a stretched or crushed wire.

 O

B+

Greater than 3 VDC: A NetSensor (SSP or ZS) is shorted on the B+ side.

 


4. Check DC Voltage | A- and Earth GND (Set to DC)

Common Issues

 O

Earth Ground

Normal Reading 2.0 - 2.5 VDC

Less than 700 MV: A- is shorted to the shield, potentially by a stretched or crushed wire.

O 

A-

Greater than 3 VDC: A NetSensor (SSP or ZS) is shorted on the A- side

 


5. Check AC Voltage | B+ and Earth GND (Set to AC)

Common Issues

 O

B+

Normal Reading

Less than 2.0 VAC

Greater than 2 VAC: Some source of voltage is shorted to the COMM.

 O

Earth Ground

Around 24 VAC: A controller is mis-phased.

 


6. Check AC Voltage | A- and Earth GND (Set to AC)

Common Issues

 O

A-

Normal Reading

Less than 2.0 VAC

Greater than 2 VAC: Some source of voltage is shorted to the COMM.

 O

Earth Ground

Around 24 VAC: A controller is mis-phased.

 

  

When wiring an ABB drive up to your BACnet MSTP network make the following connections:

 

Terminal X2

Type

(+)

(-)

Reference

Drive Only

29

30

31

Bypass

27

28

29

 

ABB recommends that when using a two conductor cable with shield that the shields not be connected  to any pin (Note that pin 29 would be unused) but simply connected together with a wire nut. However, they do say that the shields can be connected to pin 29 if the drive communication is intermittent. 

 

  • If the ABB drive does not have an E-Clipse bypass (E-Clipse is the ABB brand name for the bypass portion of the VFD) use the following settings:

 

 Parameter  

Setting

Notes

9802

 BACNET

 Sets the communications protocol of the VFD.

5302

 MAC ID

Create a unique ID. A good practice is to set this to the Infinet ID + 1000. For example, if the Infinet ID is 5 then set this to 1005.

5303

 Baud Rate

 Set the baud rate being used on your BACnet network.

5311

 Device Instance ID                 

 This is the Infinet ID and should be set to an available number between 1-127. This will display as a hexadecimal value in the BACnet side of Cyberstation.

1001

 COMM

 Set this if you want to start & stop the VFD over BACnet.

1103

 COMM

 Set this if you want to control the drive speed over BACnet.

1604

 COMM

 Set this if you want to reset VFD faults over BACnet.

 

  • If the ABB drive does include a bypass the following settings must all be entered (notice that 5302 and 5311 are now specific to the VFD portion of the unit whereas the 5002 and 5011 are specific to the bypass portion) All of these parameters as well as the parameters listed above must be entered at the bypass.

 

Parameter

Setting

Notes

5302

 Drive MAC ID

 Create a unique ID specific to the VFD.

5311

 Drive Device Instance ID

 This is the Infinet ID specific to the VFD.

5002

 Bypass MAC ID

 Create a unique ID specific to the bypass.

5011

 Bypass Instance ID

 This is the Infinet ID specific to the bypass.

 

  •  
    If the ABB drive is ACH550. Then the parameter below need to be set as a minimum. Other points will also need to be set depending on your site requirements, but the ones below will get communications up and running

 

 Parameter  

Setting

Notes

5301

  x5xx

-This parameter indicates the active protocol and its revision. It should read x50xx if BACnet is properly loaded. If this is not the case, confirm that drive parameter 9802 = BACNET (5).

5302

 MAC ID

-This parameter sets the drive’s BACnet MS/TP MAC ID. A temporary value of 0 places the protocol channel in reset.

5303

 Baud Rate

-Set the baud rate being used on your BACnet network.

5304

Set to 0

-This parameter sets the BACnet MS/TP character format as follows: 0 = 8N1 1 = 8N2 2 = 8E1 3 = 8O1.

5311

EFB PAR 11

 - Instance ID part1
This parameter, together with parameter 5317, EFB PAR 17, sets BACnet instance IDs: • For the range 1 to 65,535: This parameter sets the ID directly (5317 must be 0). For example, the following values set the ID to 49134: 5311 = 49134 and 5317 = 0. • For IDs > 65,535: The ID equals 5311’s value plus 10,000 times 5317’s value. For example, the following values set the ID to 71234: 5311 = 1234 and 5317 =7

5317

EFB PAR 17

 - Instance ID part2
This parameter works with parameter 5311 to set BACnet instance IDs. See parameter 5311.

1001

 COMM

-Set this if you want to start & stop the VFD over BACnet.

1103

 COMM

-Set this if you want to control the drive speed over BACnet.

1604

 COMM

-Set this if you want to reset VFD faults over BACnet.

 

BACnet® Protocol ACH550 AC Drives Guide

ABB Document Website