YORK YK — VSD - Low frequency detected

The control center shows VSD - Low frequency detected. The manuals also print the same message as VSD - Low Frequency Detected; both variants refer to this fault. It belongs to the variable speed compressor drive safety fault messages.

This is a safety fault on the variable speed drive (VSD) output frequency. The drive frequency has fallen more than 1 Hz below the minimum allowed running frequency and the condition has persisted, so the control center initiates a chiller shutdown. Under the current software the drive no longer has to reach the minimum frequency before the fault can be detected: a 20 second bypass and a 25 second detection time were added. Under previous software versions the fault was recognised only when the frequency had first reached the minimum allowed running frequency and then dropped below 1 Hz less than it.

• After the 20 s bypass that follows entry into System Run, the VSD frequency stays more than 1 Hz below the minimum allowed frequency for 25 s continuously. This applies to all model drives.

• Minimum allowed VSD frequency: 25 Hz for 50 Hz units and 30 Hz for 60 Hz units.
• Fault threshold: VSD frequency more than 1 Hz below the minimum allowed frequency.
• Bypass period after entering System Run: 20 s before detection starts.
• Detection time: 25 consecutive seconds below the threshold.

The fault shuts the chiller down, and the message can only be released from a stopped chiller: The message is released when the chiller is in a stopped state and the Clear button is pressed next to the listed event on the Systems Details screen.