YORK YMC2 — VSD - DC BUS PRE-REGULATION LOCKOUT

The control display reads VSD - DC BUS PRE-REGULATION LOCKOUT. The manuals list this text among the safety shutdown messages, and it appears in this exact wording only.

This shutdown means the third consecutive pre-charge/pre-regulation fault has occurred. The unit failed to complete DC bus pre-regulation — each failure being a VSD - DC BUS PRE-REGULATION fault — and after the third consecutive failure the VSD generates this lockout. If the third fault occurred during pre-regulation, the VSD logic board also disables the boost rectifier's IGBT gating signals.

• The unit failed to complete pre-regulation due to a VSD - DC BUS PRE-REGULATION fault. After such a failure, the unit must repeat pre-charge in order to attempt another pre-regulation.
• Following a failed attempt, the VSD logic board waits 10 seconds before clearing the DC-link voltage pre-regulation fault and allowing another pre-charge to start; the unit's fans and water pumps remain energized during this wait time.
• The VSD allows up to three consecutive pre-charge-related or pre-regulation-related faults; after the third consecutive fault, this shutdown is generated.

• 10 seconds — the wait time after a failed pre-regulation before the VSD logic board clears the DC-link voltage pre-regulation fault and allows the next pre-charge to start. The fans and water pumps stay energized during this wait.
• Three consecutive faults — up to three consecutive pre-charge-related or pre-regulation-related faults are allowed; the third one generates this shutdown.

The action given for this message is: When the condition clears, the chiller can be started after the CLEAR FAULTS button is pressed. No other reset steps are described for this lockout.