YORK YK — VSD - DC bus lockout - Do not cycle power

The panel shows VSD - DC bus lockout - Do not cycle power. This is the only wording the manual gives for the message; there are no variants. It belongs to the variable speed compressor drive safety fault messages of the YORK YK and applies to HYP model drives. The manual treats it as a shutdown, and the message itself carries the instruction not to cycle power.

The drive monitors the DC bus voltage whenever the unit is stopped in a mode where no command exists to energize the DC bus. Every 5 min it checks the monitored voltage against a threshold of 100 VDC. If the DC bus voltage is higher than the threshold value, the drive generates this shutdown. Read together, the message reports that DC bus voltage above 100 VDC was measured in a stop mode where no command exists to energize the DC bus, and it warns at the same time against removing and reapplying power, which the manual says makes the damage to the drive and the cost of the repair worse.

• HYP model drives: the unit is stopped in a mode where no command exists to energize the DC bus, and the DC bus voltage monitored every 5 min is higher than the 100 VDC threshold value.

1. Do not remove and reapply power while the message is active. If power is removed, and then reapplied without correcting this problem more damage occurs to the drive, and the repair is more costly.
2. Have the VSD rectifier modules tested; the manual makes this testing a condition for starting the chiller again.

• DC bus voltage threshold: 100 VDC — the level the monitored DC bus voltage is checked against.
• Check interval: 5 min — the DC bus voltage is monitored and checked against the threshold every 5 min while the unit is stopped in a mode where no command exists to energize the DC bus.
• Applicability: the manual ties this monitoring and this shutdown to HYP model drives.

The manual describes no reset procedure for this message, and it forbids the usual move of cycling power. The chiller can be started again only after the condition has cleared and the VSD rectifier modules have been tested: When the condition clears and the VSD rectifier modules are tested, then the chiller can be started. Removing and reapplying power without correcting the problem is not a reset — it causes more damage to the drive and a more costly repair.