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Form QTC4-NM2
Issue date: 05/12/2023
Table 35 - Troubleshooting guide, cont'd
Problem
System fault:
high discharge pressure
System fault:
high discharge temperature
System fault:
high motor temperature
System fault:
low suction pressure
System fault:
discharge pressure limiting
System fault:
low economizer superheat
Note: Always remove power to the chiller and ensure the DC Bus voltage has bled off.
Quantech
Possible cause
Coils dirty
Coils are damaged
Fans not operating
System is overcharged
Discharge Temperature Sensor is defective
Condenser Fans not operating or are run-
ning backwards
Coils dirty
High superheat
High motor temperature input from one of the
sensors
Low charge
Transducer reads incorrectly
Suction temp. sensor reads incorrectly
Low flow
Condenser drain valve not operating
Condenser or drain valve defective
Discharge transducer is defective
Ambient temp. very high
Fans not operating
Remote or local discharge pressure
load limiting is programmed
Economizer line temperature sensor is
defective
Economizer transducer is defective
Economizer feed valve malfunction
Economizer line solenoid purge valve
malfunction
Section 9 - Maintenance
Action
Check and clean coils
Comb out fins
Check fan fuses
Check fan rotation
Check fan motor/blade
Remove charge and check subcooling
Check sensor
Check fans
Check and clean coils
Measure superheat with gauges and
thermocouple. Determine cause
Refrigerant charge low. Check subcooling
Excess charge in system, High discharge
pressure. Check subcooling
High Superheat. Drain or 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
Check subcooling
Check transducer against a gauge
Check sensor against a thermocouple
Check flow
Check drain valve operation.
Check superheat
Check drain valve operation
check superheat
Check transducer against a gauge
Normal operation
Check fan operation
Normal operation
Check temperature sensor
Check transducer against a gauge
Check economizer feed valve operation
Check economizer line solenoid purge
valve operation
9
177
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