On the display
The panel reads UNIT VSD COMMUNICATIONS FAILURE. The manuals list this fault among the unit safeties and give only this one wording of the message.
What it means
The Chiller Control Board has either never established communications with the VSD Logic Board or has lost them while the chiller was running. It is a unit-level safety whose job is to stop the unit from trying to run when communications never initialize. If it trips during operation, all compressors shut down with a controlled ramped shutdown; if communications never came up at power-up, the chiller is kept from operating at all.
Why it appears
- At power-up the Chiller Control Board opens an initialization exchange with the VSD Logic Board in which it asks for the number of compressors and the VSD software version; if this connection fails to occur, the chiller is blocked from operating.
- During normal operation the Chiller Control Board receives no valid response to its messages for 8 seconds, so the unit shuts all compressors down on a Comms fault.
Setpoints and thresholds
- 8 seconds — the longest the Chiller Control Board can go without a valid response to its messages during operation before all compressors are shut down on a Comms fault.
Reset and restart
The fault is self-clearing: The fault automatically resets when the Chiller Control Board receives a valid response from the VSD for a data request.
Until communications is established, the unit is inhibited from starting, and the Chiller Control Board continues to send messages to the VSD while the fault is present.
Questions engineers ask
What does UNIT VSD COMMUNICATIONS FAILURE mean on a York YCAV?
The Chiller Control Board never initialized communications with the VSD Logic Board, or received no valid response to its messages for 8 seconds during operation. All compressors shut down with a controlled ramped shutdown.
How do I reset a VSD communications failure on a YCAV chiller?
The fault resets automatically once the Chiller Control Board receives a valid response from the VSD to a data request. Until communications is established, the unit is inhibited from starting.
Why does my YCAV show UNIT VSD COMMUNICATIONS FAILURE?
Either the power-up initialization — in which the Chiller Control Board asks the VSD Logic Board for the number of compressors and the VSD software version — never completed, or the board got no valid response to its messages for 8 seconds while running.
Can the chiller run while UNIT VSD COMMUNICATIONS FAILURE is showing?
No. The unit is inhibited from starting until communications is established; in the meantime the Chiller Control Board continues sending messages to the VSD.
Messages next to this one
The same message on other models
Source
Written from the manufacturer's manuals for the YORK YCAV; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YCAV messages: fault codes · YORK YCAV documentation · YORK manuals