SECTION 9 - MAINTENANCE
JOHNSON CONTROLS
179
Form 201.47-ICOM1
Issue date: 17/11/2022
9
Table 32 - Troubleshooting guide (cont'd)
Problem Possible cause Action
System fault:
High discharge pressure
Coils dirty. Check and clean coils.
Coils are damaged. Comb out ns.
Fans NOT operating.
Check fan fuses.
Check fan rotation.
Check fan motor/blade.
System is overcharged. Remove charge and check subcooling.
System fault:
High discharge temperature
Discharge Temperature Sensor is defective. Check Sensor.
Condenser Fans NOT operating or are run-
ning backwards.
Check Fans.
Coils dirty. Check and clean Coils.
High Superheat.
Measure Superheat with gauges and
thermocouple. Determine cause.
System fault:
High motor temperature
High Motor temperature input from one of the
sensors.
Refrigerant charge low. Check subcooling.
Excess charge in system, High discharge
pressure. Check subcooling.
High Superheat. Drain/Feed Valves NOT
controlling. Isolate cause.
Motor Sensor reading incorrectly. Program
panel to ignore a single sensor.
Economizer Solenoid energized at low
speeds. Valve is leaking through.
System fault:
Low suction pressure
Low charge. Check subcooling.
Transducer reads incorrectly. Check transducer against a gauge.
Suction Temp. Sensor reads incorrectly. Check sensor against a thermocouple.
Low ow. Check ow.
Condenser Drain Valve NOT operating.
Check Drain Valve operation.
Check superheat.
Condenser or Drain Valve defective.
Check Drain Valve operation.
Check superheat.
System fault:
Discharge pressure limiting
Discharge Transducer is defective. Check transducer against a gauge.
Ambient Temp. very high. Normal operation.
Fans not operating. Check fan operation.
Remote or local discharge pressure
load limiting is programmed.
Normal operation.
System fault:
Low economizer superheat
Economizer line temperature sensor is
defective
Check temperature sensor
Economizer transducer is defective Check transducer against a gauge
Economizer feed valve malfunction Check economizer feed valve operation
Economizer line solenoid purge valve mal-
function
Check economizer line solenoid purge
valve operation
Note: Always remove power to the chiller and ensure the DC Bus voltage has bled o.
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