York YCAL Series Installation Operation & Maintenance page 155

FORM 150.66-NM3
ISSUE DATE: 09/25/2020
TABLE 32 – TROUBLESHOOTING (CONT'D)
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 temp. cutout (glycol only).
2. Micro panel setpoint/range values
improperly programmed.
3. Chilled liquid flow too low.
4. Defective LWT or RWT sensor.
(ensure 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. Ensure 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 temp. 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 temp./
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
+/- 2 degrees. Refer to "Service"
section for RWT/LWT temp./
voltage table.
3. Replace defective part.
4. Diagnose cause of failure and
replace.
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