213
JOHNSON CONTROLS
SECTION 9 – SERVICE AND TROUBLESHOOTING
FORM 150.67-NM1
ISSUE DATE: 4/28/2017
9
TABLE 37 - TROUBLESHOOTING
PROBLEM CAUSE SOLUTION
HIGH DISCHARGE PRESSURE FAULT
1. Condenser fans not operating or
operating backwards.
1. Check fan motor, fuses and
contactors. Assure fan blows air
upward.
2. Too much refrigerant. 2. Remove refrigerant.
3. Air in refrigerant system. 3. Evacuate and recharge system.
4. Defective discharge pressure
transducer.
4. Replace discharge pressure
transducer. Refer to Service
section for pressure/voltage
formula.
LOW LIQUID TEMP FAULT
1. Improperly adjusted leaving chilled
liquid temperature cutout (glycol only).
1. Re-program the leaving chilled
liquid temperature cutout.
2. Micro panel setpoint/range values
improperly programmed.
2. Re-adjust setpoint/range.
3. Chilled liquid ow too low. 3. Increase chilled liquid ow –
refer to Limitations in Installation
section.
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).
4. Compare sensor against a
known good temperature
sensing device. Refer to Service
section for temperature/ voltage
table.
MP / HPCO FAULT
1. Compressor internal motor protector
(MP) open.
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. External overload tripped. 2. Determine cause and reset.
3. HPCO switch open. 3. See High Press. Disch. fault.
4. Defective HPCO switch. 4. Replace HPCO switch.
5. Defective CR relay. 5. Replace relay.
COMPRESSOR(S) WON’T START
1. Demand not great enough. 1. No problem. Consult Installation
Manual to aid in understanding
compressor operation and
capacity control.
2. Defective water temperature sensor. 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. Contactor/Overload failure. 3. Replace defective part.
4. Compressor failure. 4. Diagnose cause of failure and
replace.
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