YORK YMC2 — VSD - PRECHARGE LOCKOUT

The control center shows VSD - PRECHARGE LOCKOUT. The manual lists it among the safety shutdown messages for this model and prints it in one form only, so there are no display variants to look for.

This shutdown is generated after the third consecutive pre-charge fault. The fault table gives the meaning as: third consecutive pre-charge fault. The VSD logic board allows up to three consecutive pre-charge-related faults; the first two faults are each cleared after a delay and a new pre-charge attempt, and only the third consecutive fault produces this lockout.

• The unit fails to complete pre-charge. The manual names two messages as the reasons a pre-charge attempt fails: VSD - PRECHARGE - LOW DC BUS VOLTAGE or VSD - PRECHARGE - HIGH DC BUS VOLTAGE.
• After each such fault, the VSD logic board times 10 seconds before clearing the fault and allowing another pre-charge to start; the unit's fan(s) and water pump(s) remain energized during this time.
• The VSD allows up to three consecutive pre-charge-related faults; after the third consecutive pre-charge-related fault, this shutdown is generated.

1. Identify which pre-charge-related message preceded the lockout — VSD - PRECHARGE - LOW DC BUS VOLTAGE or VSD - PRECHARGE - HIGH DC BUS VOLTAGE. One of these is the reason each pre-charge attempt failed.
2. Confirm the condition that produced the pre-charge faults has cleared; the manual permits a start only when the condition clears, so the lockout remains in place until then.

The manual's action for this safety shutdown is: When the condition clears, the chiller can be started after the CLEAR FAULTS button is pressed. The unit therefore does not come back on its own: once the underlying pre-charge condition has cleared, press the CLEAR FAULTS button and start the chiller.