YORK YK — VSD - Precharge lockout

The panel reads VSD - Precharge lockout — this is the only wording the manual prints for the message. It is listed with the variable speed compressor drive safety fault messages, and the control center classifies it as a safety shutdown message, so it appears when the unit has tripped and locked out.

The VSD has failed to make precharge. On each failed attempt the precharge relay drops out for 10 s, and during that drop-out period the VSD fans and water pumps remain energized so that the precharge resistors can cool. After the 10 s cool-down the drive initiates precharge again, and it attempts precharge three consecutive times. If the VSD fails to make precharge on three consecutive tries, the unit shuts down, locks out and displays this message. The manual applies this to all model drives.

• The VSD fails to make precharge.
• Failed attempts repeat: the precharge relay drops out for 10 s while the VSD fans and water pumps stay energized to permit the precharge resistors to cool, and precharge is initiated again after the cool-down period.
• The safety shutdown message is generated after the third consecutive precharge-related fault — precharge failing on three consecutive tries.

The unit stays shut down and locked out until the event is cleared from the control center. The manual's instruction: The chiller can be started after the Clear button is pressed next to the listed event on the Systems Details screen.