YORK YCAV — SYS X VSD RUN RELAY

The panel prints SYS X VSD RUN RELAY; X is the system number. The manual's fault tables show the entry with a placeholder between the system number and the message, and the manual states that this position reads FAULT when the condition restarts once cleared or LOCKOUT when the unit is locked out. The message is one of the VSD safeties (faults) of this chiller.

This is a software-generated VSD run relay fault: the hardware and software run signals did not match within the 5-second window. On 2-compressor units it is a system fault; on 3- and 4-compressor units it is combined as a 1/3 or 2/4 system fault. If the chiller is running when it trips, it shuts down with a controlled ramped shutdown. The status carried in the message tells you whether the unit is in a FAULT condition, which restarts when cleared, or in LOCKOUT.

• A 5-second timer starts when either run command is received — there are two types, hardware and software. The system faults if the missing run signal is not asserted inside that 5-second window.
• If either run signal is disabled while the VSD is running, the remaining run signal has to be disabled within 5 seconds of the VSD shutdown; if it is not, the system faults.

1. Identify the two run signals being compared: the hardware run signal, which comes from the SYS X VSD Run Signal to the VSD Logic Board, and the software run signal, which arrives through the comms from the Chiller Control Board.
2. Confirm that the run signal that was missing asserts within the 5-second window after the run command.
3. Where one signal dropped while the VSD was running, confirm that the remaining run signal is disabled within 5 seconds after the VSD is shut down.

• 5-second window — time allowed for the missing run signal to assert after the run command is received.
• 5 seconds after VSD shutdown — time allowed for the remaining run signal to be disabled when the other dropped while running.
• 120-second anti-recycle timer — the delay the auto-restart waits out before the unit autostarts.
• 3rd fault in 90 minutes — the repeat count within this period that produces a lockout.

This is an auto-restart safety: the unit autostarts after the 120-second anti-recycle timer times out. It locks out on the 3rd fault in 90 minutes. A lockout will not restart until the operator clears the fault using the keypad.