Carrier 48/50HJ004-014 specifications Heating and Cooling Troubleshooting, Problem Cause Remedy

Table 3 — 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, con-	Replace component.
	trol relay, or capacitor.
	Insufficient line voltage.	Determine cause and correct.
	Incorrect or faulty wiring.	Check wiring diagram and rewire correctly.
	Light Commercial Thermidistat program in UC1	Check Light Commercial Thermidistat program. See Step 5
	or UC2 mode.	— Conduct Light Commercial Thermidistat Start-Up and
		Checkout on page 33.
	Defective fan motor.	Replace fan motor.
Compressor will not start but	Faulty wiring or loose connection 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 run/start capacitor, overload, start relay,	Determine cause and replace.
	Time Guard® device.
	No DEHUM signal from Light Commercial	Check for DEHUM signal on Light Commercial Thermidistat
	Thermidistat.	LCD display.
	Time Guard device not timed out.	Allow time for Time Guard device to recycle unit.
Compressor cycles (other	Refrigerant overcharge or undercharge.	Recover refrigerant, evacuate system, and recharge to
than normally satisfying		nameplate.
thermostat).	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 run/start capacitor, overload, or start	Determine cause and replace.
	relay.
	Faulty outdoor-fan (cooling) or indoor-fan (heat-	Replace.
	ing) motor or capacitor.
	Restriction in refrigerant system.	Locate restriction and remove.
Suction pressure greater than	Defective TXV.	Replace TXV.
100 psig in Cooling mode.
Excessive head pressure.*	Dirty air filters.	Replace filters.
	Dirty coils.	Clean coils.
	Refrigerant overcharged.	Recover 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 filters or coils.	Replace filter, clean coils.
	Low refrigerant charge.	Check for leaks; repair and recharge.
	Metering device or low side restricted.	Remove source of restriction.
	Insufficient indoor airflow.	Increase air quantity. Check filter and replace if necessary.

LEGEND

TXV — Thermostatic Expansion Valve

*Energy recovery section uses TXVs with a 100 psig maximum operating pressure (MOP) feature to limit suction pressure in Cooling mode at high temperatures. Always consult charging chart for correct operating pressures.

Table 4 — Supply-Air Damper Troubleshooting

PROBLEM	CAUSE	REMEDY
Damper does not open; fan(s) off.	OCR not energized (thermostat in Unoccupied	Check Light Commercial Thermidistat program
	mode).	settings (see Step 5 — Light Commercial Thermi-
		distat Start-Up and Checkout section, page 33).
	OCR defective.	Replace OCR.
	Damper jammed.	Free damper.
	Damper motor defective.	Replace damper motor.
	Loose wiring.	Check wiring and correct.
Damper will not close.	Damper jammed.	Free damper.
	Motor return spring broken.	Replace motor.
LEGEND
OCR — Occupied Relay

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