York YK-EP Operation And Maintenance Manual page 219

the total RMS value of all the harmonic current supplied by the main power to the VSD divided by
the chiller Full Load Amps, in percent. A standard VSD, less the optional filter typically has an input
current TDD level on the order of 28-30%. The chiller can be started after the Operator presses the
WARNING RESET button.
VSD – Low Frequency Detected
After a 20 second bypass after entering System Run, if the VSD frequency decreases to below 1 Hz
less than the minimum allowed frequency for 25 continuous seconds, this shutdown is initiated.
The minimum allowed frequency for the VSD is 25 Hz for 50 Hz units; 30 Hz for 60 Hz units. The
Operator must press the WARNING RESET button to reset the fault.
YK-EP Style B Centrifugal Chiller 219