York YCWL0056SE Installation Operation & Maintenance page 166

SECTION 9 – SERVICE AND TROUBLESHOOTING
TABLE 26 - TROUBLESHOOTING (CONT'D)
PROBLEM
HIGH DISCHARGE PRESSURE FAULT
LOW LIQUID TEMP FAULT
MP / HPCO FAULT
COMPRESSOR(S) WON'T START
166
CAUSE
1. Tower fans not operating
2. Too much refrigerant.
3. Air in refrigerant system.
4. Defective discharge pressure trans-
ducer.
5. Dirty condenser tubes
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.
(assure the sensor is properly in-
stalled 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.
FORM 201.26-NM1
ISSUE DATE: 1/19/2018
SOLUTION
1. Check tower.
2. Remove refrigerant.
3. Evacuate and recharge system.
4. Replace discharge pressure
transducer. Refer to Service sec-
tion for pressure/voltage formula.
5. Clean condenser tubes.
1. Re-program the leaving chilled
liquid temp. cutout.
2. Re-adjust setpoint/range.
3. Increase chilled liquid flow –
Refer to Limitations in
SECTION 4 - INSTALLATION.
4. Compare sensor against a
known good temperature sens-
ing device. Refer to Service sec-
tion 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 understand-
ing 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./volt-
age table.
3. Replace defective part.
4. Diagnose cause of failure and
replace.
JOHNSON CONTROLS