Carrier 30HW018-040, 30HL050, 30HK040-060 Ð Troubleshooting, Compressor cycles control

COOLING LOAD SATISFIED Ð Unit shuts down if cool- ing load is satis®ed. Unit restarts if required after comple- tion of 5-minute timer cycle.

THERMISTOR FAILURE Ð If thermistor fails in open mode, the temperature controller shuts down the unit in an out-of- range condition. Replace the thermistor. Unit restarts auto- matically after completion of a 5-minute timer cycle, and when the leaving cooler chilled ¯uid temperature rises above the upper deadband limit of the temperature controller.

NOTE: If the thermistor fails in closed mode, the tempera- ture controller keeps trying to load up.

If unit stoppage occurs more than once as a result of any of the safety devices listed, determine and correct cause before attempting another restart.

Table 14 Ð Troubleshooting

SYMPTOMS	CAUSE	REMEDY
Compressor does	Power line open	Reset circuit breaker.
not run
	Control fuse or circuit breaker opens	Check control circuit for ground or short. Reset breaker
		and replace fuse.
	Compressor overtemperature sensor open	Find cause of high temperature and reset controls.
	Tripped power breaker	Check the controls. Find the cause of trip and
		reset breaker.
	Condenser circulating pump not running	Power off Ð restart.
		Pump binding Ð free pump.
		Incorrect wiring Ð rewire.
		Pump motor burned out Ð replace.
	Loose terminal connection	Check connections.
	Improperly wired controls	Check wiring and rewire if necessary.
	Low line voltage	Check line voltage Ð determine location of voltage drop
		and remedy de®ciency.
	Compressor motor defective	Check motor winding for open or short. Replace
		compressor if necessary.
	Seized compressor	Replace compressor.
Compressor cycles	Loss of charge control erratic in action	Repair leak and recharge.
off on loss of
		Replace control.
charge
	Low refrigerant charge	Add refrigerant.
	Low suction temperature	Raise cooler leaving ¯uid temperature set point.
	Compressor suction valve leaking	Replace valve plate.
	Plugged compressor suction strainer	Clean or replace strainer.
	Compressor suction shutoff valve partially closed	Open valve.
Compressor cycles	Thermistor failure	Replace thermistor.
off on out of range
	System load was reduced faster than	Unit will restart after ¯uid temperature rises back into the
condition
	controller could remove stages	control band. Avoid rapidly removing system load.
Compressor cycles control	Temperature controller deadband setting is	Raise deadband setting.
steps rapidly	too low
Compressor shuts	High-pressure control acting erratically	Replace control.
down on high-
	Compressor discharge valve partially closed	Open valve or replace (if defective).
pressure control
	Air in system	Purge system.
	Condenser scaled/dirty	Clean condenser.
	Receiver not properly vented Ð refrigerant	Repipe as required to provide adequate venting.
	backs up into evaporator condenser
	Condenser water pump or fans not operating	Start pump Ð repair or replace if defective.
	System overcharged with refrigerant	Reduce charge.
Unit operates too long	Low refrigerant charge	Add refrigerant.
or continuously
	Control contacts fused	Replace control.
	Air in system	Purge system.
	Partially plugged or plugged expansion valve	Clean or replace as needed.
	or ®lter drier
	Defective insulation	Replace or repair as needed.
	Service load	Keep doors and windows closed.
	Inefficient compressor	Check valves, and replace if necessary.
Unusual or loud system	Piping vibration	Support piping as required.
noises
		Check for loose pipe connections.
	Expansion valve hissing	Add refrigerant.
		Check for plugged liquid line ®lter drier.
	Compressor noisy	Check valve plates for valve noise.
		Replace compressor (worn bearings).
		Check for loose compressor holddown bolts.

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