YORK YMC2 — VSD - PRECHARGE - LOW DC BUS VOLTAGE 1

The display reads VSD - PRECHARGE - LOW DC BUS VOLTAGE 1, exactly as the manuals print it; no alternate variants are listed. The YMC2 manual places the message among the cycling shutdown messages, and it belongs to the pre-charge stage of the VSD.

This cycling shutdown is generated by the VSD when a pre-charge attempt does not bring the DC bus voltage up in time. During pre-charge, the DC bus voltage must reach the minimum threshold determined by the Line Voltage Setpoint within 4 seconds after the pre-charge signal has been commanded. If the voltage does not meet that condition within those 4 seconds, this shutdown is generated.

• The DC bus voltage did not reach at least the low threshold, which is determined by the Line Voltage Setpoint, within 4 seconds after the pre-charge signal was commanded.

• Minimum DC bus voltage threshold during pre-charge, by Line Voltage Setpoint: 460 V — 50 V; 380/415 V — 41 V; 230 V — 25 V.
• Time allowed to reach the threshold after the pre-charge signal is commanded: 4 seconds.
• Wait before the fault is cleared and another pre-charge is allowed: 10 seconds.
• Consecutive pre-charge-related faults allowed before the safety shutdown: three.

Recovery from this shutdown is automatic and timed by the VSD logic board. The logic board waits 10 seconds before clearing the fault and allowing another pre-charge to start; during that time the VFD's fan(s) and water pump(s) remain energized. If pre-charge fails again, the cycle repeats — up to three consecutive pre-charge-related faults are allowed. After the third consecutive pre-charge-related fault, the Safety Shutdown message VSD - PRECHARGE LOCKOUT is generated.