On the display
The panel shows UNIT VSD COMMUNICATIONS FAILURE. This is a unit-level safety from the YVAA's unit safeties group.
What it means
The Chiller Control Board has lost communications with the VSD Logic Board. If the Chiller Control Board never initializes communications with the VSD Logic Board, the fault prevents the unit from trying to run. If communications are lost while the chiller is operating, all compressors shut down with a controlled ramped shutdown. The unit is inhibited from starting until communications is established, and the Chiller Control Board continues to send messages to the VSD while the fault is active.
Why it appears
- On power-up, the Chiller Control Board fails to initialize communications with the VSD Logic Board — no reply from the VSD Logic Board within 8 seconds.
- During normal operation, the Chiller Control Board receives no valid response to messages for 8 seconds.
Setpoints and thresholds
- 8 seconds — on power-up, the fault occurs if the VSD Logic Board has not replied within this time.
- 8 seconds — during normal operation, the fault occurs if no valid response to messages is received for this long.
- 3 VSD unit faults within 90 minutes — the unit locks out on the last fault.
Reset and restart
The fault resets automatically: it clears as soon as the Chiller Control Board receives a valid response from the VSD for a data request, and the unit can then start again. If any 3 VSD unit faults occur within 90 minutes, the unit locks out on the last fault. A VSD lockout requires a manual reset using the system switches — both system switches must be cycled OFF and ON to clear
.
Questions engineers ask
What does UNIT VSD COMMUNICATIONS FAILURE mean on a YORK YVAA?
It means the Chiller Control Board has lost communications with the VSD Logic Board. The unit is inhibited from starting until communications is established, and an operating unit shuts down all compressors with a controlled ramped shutdown.
Why does my YVAA show a VSD communications failure?
Either the VSD Logic Board did not reply within 8 seconds on power-up, or during normal operation the Chiller Control Board received no valid response to its messages for 8 seconds.
How do I clear UNIT VSD COMMUNICATIONS FAILURE on a YVAA?
It resets automatically when the Chiller Control Board receives a valid response from the VSD for a data request. If the unit is locked out after 3 VSD unit faults within 90 minutes, cycle both system switches OFF and ON to clear the lockout.
Does the YVAA lock out after repeated VSD faults?
Yes. If any 3 VSD unit faults occur within 90 minutes, the unit locks out on the last fault, and clearing it requires a manual reset by cycling both system switches OFF and ON.
Messages next to this one
The same message on other models
Source
Written from the manufacturer's manuals for the YORK YVAA; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YVAA messages: fault codes · YORK YVAA documentation · YORK manuals