York YK-EP Operation And Maintenance Manual page 205

If the Half DC Link Voltage does not remain within plus or minus 106VDC of the DC Link Voltage
divided by 2 during the pre-charge interval, this shutdown is performed.
VSD – High Internal Ambient Temperature
The ambient temperature monitored is actually the temperature detected by a component
mounted on the VSD Logic Board. The high ambient trip threshold is set for 140°F. Some potential
causes for this shutdown are: internal VSD fan failure, VSD water pump failure or an entering
condenser water temperature that exceeds the allowable limit for the job. Additional causes for the
shutdown are:
• Plugged Strainer – The standard 1.5" Y-strainer contains a woven mesh element with 20
stainless steel wires per inch. This has been found to work adequately on most applications.
Some users may have very dirty condenser water, which can cause the strainer to plug.
Locations with special conditions may want to consider a dual strainer arrangement with
quarter turn valves, to permit cleaning of one strainer with the unit still on line.
• Plugged Heat-exchanger – In cases where the strainer plugs frequently, the heat-exchanger
may eventually plug or become restricted to the point of reduced flow. At this point, we
suggest you back-flush the heat-exchanger by reversing the two rubber hoses which supply
condenser water to-from the heat-exchanger. If the rust cannot be back-flushed the heat-
exchanger might have to be replaced.
• Low Condenser Flow – The VSD system requires 8 feet of pressure drop across the heat
exchanger to maintain adequate GPM. If the pressure drop is less than 8 feet, it will be
necessary to correct the flow problem or add a booster pump as is applied on retrofit chillers.
VSD – Invalid Current Scale Selection
Since the part number of the VSD Logic Board is the same on all horsepower sizes, the position
of Program Jumpers tells the Logic Board the size of the VSD employed. This allows the VSD to
properly scale the output current. If the jumper configuration is invalid, a shutdown is performed
and this message is generated. Refer to Variable Speed Drive – Service Instructions (Form 160.00-M1).
VSD – Low Phase A Inverter Heatsink Temperature
(Style D VSD)
A heatsink temperature sensor indicating a temperature less than 37°F will cause the chiller to shut
down and display this message. In most cases, the problem will be an open transmitter or broken
wiring to the transmitter. The normal transmitter resistance is 10K ohms at 77°F.
VSD – Low Phase B Inverter Heatsink Temperature
(Style D VSD)
See Low Phase A Inverter Heatsink Temperature message above.
VSD – Low Phase C Inverter Heatsink Temperature
(Style D VSD)
See Low Phase A Inverter Heatsink Temperature message above.
VSD – Low Converter Heatsink Temperature
If VSD part number is 371-02767-XXX (60 Hz) or 371-03700-XXX (50 Hz), a heatsink temperature
sensor indicating a temperature of less than 37°F will cause the chiller to shutdown and display
this message. In most cases, the problem will be an open transmitter or broken wiring to the
transmitter. The normal transmitter resistance is 10K ohms at 77°F.
VSD – Low Phase A Inverter Baseplate Temperature
(VSD part number 371-03789-xxx (503 HP 60 Hz; 419 HP 50 Hz)
YK-EP Style B Centrifugal Chiller 205