York YK Style H Operation Manual page 180

actual Bus Voltage Imbalance conditions are caused by a shorted capacitor or a leaky or shorted
IGBT transistor in an output phase bank assembly. This usually indicates the VSD requires service.
VSD – DC Bus Voltage Imbalance
(575V/60 Hz applications)
If the Half DC Link Voltage does not remain within plus or minus 106 VDC of the DC Link Voltage
divided by 2 while running, this shutdown is performed.
VSD – Precharge – DC Bus Voltage Imbalance
This message indicates the same as the VSD-DC Bus Voltage Imbalance message above, except the
condition occurred during the prelube period.
VSD – Precharge – DC Bus Voltage Imbalance
(575V/60 Hz applications)
If the Half DC Link Voltage does not remain within plus or minus 106 VDC 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 (60°C). 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 in. (3.81 cm) 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.
180 Model YK Style H Centrifugal Liquid Chillers with OptiView Control Center