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Poor data communications, communications failure or packet being corrupted

Issue

Poor communications, communications failure or packet being corrupted

Environment

Communications networks, BACnet MSTP, LON FT10, Infinet, Modbus RTU, Ethernet, EMC (Electromagnetic compatibility)

VSD Variable Speed Drive, VFD Variable Frequency Drive, Inverter Drive

Cause

Electrical Interference from Inverter (variable speed drives or VSD)

Radiated or Induced RFI (Radio Frequency Interference)

Resolution

A VSD has the potential to create a large amount of electrical noise, to avoid causing issues it is vital they are installed as the manufacturer's instructions.  (Other devices also have this potential)

Our systems are often used to control VSDs on fan motors, so if poor communications is found during the commissioning process, then try stopping all the fans in the area then re-testing the communications.

A recent example was seen where LON FT10 communication was working ok until some VSDs were started, at this point LON devices and Object went offline intermittently.
When the all the VSDs were stopped the communication become completely stable.
It was then easy to find which VSD was causing the problem and correct the VSD installation.
In this case a LON analyzer would also have helped diagnose the issue.

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Last update:
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