York YCAL0019 Installation, Operation And Maintenance Manual page 213

FORM 150.67-NM1
ISSUE DATE: 4/28/2017
TABLE 37 - TROUBLESHOOTING
PROBLEM
HIGH DISCHARGE PRESSURE FAULT
LOW LIQUID TEMP FAULT
MP / HPCO FAULT
COMPRESSOR(S) WON'T START
JOHNSON CONTROLS
CAUSE
1. Condenser fans not operating or
operating backwards.
2. Too much refrigerant.
3. Air in refrigerant system.
4. Defective discharge pressure
transducer.
1. Improperly adjusted leaving chilled
liquid temperature cutout (glycol only).
2. Micro panel setpoint/range values
improperly programmed.
3. Chilled liquid flow too low.
4. Defective LWT or RWT sensor.
(assure the sensor is properly
installed in the bottom of the well with
a generous amount of heat conductive
compound).
1. Compressor internal motor protector
(MP) open.
2. External overload tripped.
3. HPCO switch open.
4. Defective HPCO switch.
5. Defective CR relay.
1. Demand not great enough.
2. Defective water temperature sensor.
3. Contactor/Overload failure.
4. Compressor failure.
SECTION 9 – SERVICE AND TROUBLESHOOTING
SOLUTION
1. Check fan motor, fuses and
contactors. Assure fan blows air
upward.
2. Remove refrigerant.
3. Evacuate and recharge system.
4. Replace discharge pressure
transducer. Refer to Service
section for pressure/voltage
formula.
1. Re-program the leaving chilled
liquid temperature cutout.
2. Re-adjust setpoint/range.
3. Increase chilled liquid flow –
refer to Limitations in Installation
section.
4. Compare sensor against a
known good temperature
sensing device. Refer to Service
section for temperature/ voltage
table.
1. Verify refrigerant charge is not
low. Verify superheat setting of
10° - 15°F (5.6° - 8.3°C). Verify
correct compressor rotation.
Verify compressor is not over
loaded.
2. Determine cause and reset.
3. See High Press. Disch. fault.
4. Replace HPCO switch.
5. Replace relay.
1. No problem. Consult Installation
Manual to aid in understanding
compressor operation and
capacity control.
2. Compare the display with a
thermometer. Should be within
plus or minus 2 degrees. Refer
to Service section for RWT/LWT
temperature/voltage table.
3. Replace defective part.
4. Diagnose cause of failure and
replace.
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