Carrier 50TFQ008-012 specifications Heating and Cooling Troubleshooting

Table 28 — Heating and Cooling Troubleshooting

PROBLEM	CAUSE	REMEDY
Compressor and Outdoor Fan	Power failure.	Call power company.
Will Not Start.	Fuse blown or circuit breaker tripped.	Replace fuse or reset circuit breaker.
	Defective thermostat, contactor, transformer, or	Replace component.
	control relay.
	Insufficient line voltage.	Determine cause and correct.
	Incorrect or faulty wiring.	Check wiring diagram and rewire correctly.
	Thermostat setting too high.	Lower thermostat setting below room
		temperature.
	High-pressure switch tripped.	See problem ‘‘Excessive Head Pressure.’’
	Low-pressure switch tripped.	Check for leaks, repair, and recharge.
	Freeze-up protection thermostat tripped.	See problem ‘‘Suction Pressure Too Low.’’
Compressor Will Not Start But	Faulty wiring or loose connections in compressor	Check wiring and repair or replace.
Outdoor Fan Runs.	circuit.
	Compressor motor burned out, seized, or internal	Determine cause. Replace compressor.
	overload open.
	Defective overload.	Determine cause and replace.
	One leg of 3-phase power dead.	Replace fuse or reset circuit breaker.
		Determine cause.
Compressor Cycles (Other Than	Refrigerant overcharge or undercharge.	Recover refrigerant, evacuate system, and
Normally Satisfying Thermostat).		recharge to nameplate.
	Defective compressor.	Replace and determine cause.
	Insufficient line voltage.	Determine cause and correct.
	Blocked outdoor coil or dirty air filter.	Determine cause and correct.
	Defective overload.	Determine cause and replace.
	Defective thermostat.	Replace thermostat.
	Faulty outdoor-fan (cooling) or indoor-fan (heating)	Replace.
	motor or capacitor.
	Restriction in refrigerant system.	Locate restriction and remove.
Compressor Operates Continuously.	Dirty air filter.	Replace filter.
	Unit undersized for load.	Decrease load or increase unit size.
	Thermostat set too low.	Reset thermostat.
	Low refrigerant charge.	Locate leak, repair, and recharge.
	Leaking valves in compressor.	Replace compressor.
	Air in system.	Recover refrigerant, evacuate system, and
		recharge.
	Outdoor coil dirty or restricted.	Clean coil or remove restriction.
	Dirty air filter.	Replace filter.
Excessive Head Pressure.	Dirty outdoor coil.	Clean coil.
	Refrigerant overcharged.	Remove excess refrigerant.
	Air in system.	Recover refrigerant, evacuate system, and
		recharge.
	Condensing air restricted or air short-cycling.	Determine cause and correct.
Head Pressure Too Low.	Low refrigerant charge.	Check for leaks, repair, and recharge.
	Compressor valves leaking.	Replace compressor.
	Restriction in liquid tube.	Remove restriction.
Excessive Suction Pressure.	High heat load.	Check for source and eliminate.
	Compressor valves leaking.	Replace compressor.
	Refrigerant overcharged.	Recover excess refrigerant.
Suction Pressure Too Low.	Dirty air filter (cooling) or dirty outdoor coil	Replace filter or clean coil.
	(heating).
	Low refrigerant charge.	Check for leaks, repair, and recharge.
	Metering device or low side restricted	Remove source of restriction.
	Insufficient indoor airflow (cooling mode).	Increase air quantity. Check filter and replace if
		necessary.
	Temperature too low in conditioned area.	Reset thermostat.
	Field-installed filter drier restricted.	Replace.
	Outdoor ambient temperature below 25 F.	Install low-ambient kit.
Compressor No. 2 Will Not Run.	Unit in economizer mode.	Proper operation; no remedy necessary.

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