Carrier 50HQP072-120 specifications Troubleshooting, Fault Heating Cooling Possible Cause Solution

Table 18 — Troubleshooting

	FAULT	HEATING	COOLING	POSSIBLE CAUSE	SOLUTION
Main Power Problems		X	X	Green Status LED Off	Check line voltage circuit breaker and disconnect.
					Check for line voltage between L1 and L2 on the contactor.
					Check for 24-vac between R and C on controller.
					Check primary/secondary voltage on transformer.
HP Fault — Code 2			X	Reduced or no water flow in	Check pump operation or valve operation/setting.
High Pressure				cooling
					Check water flow adjust to proper flow rate.
			X	Water temperature out of	Bring water temperature within design parameters.
				range in cooling
		X		Reduced or no airflow in	Check for dirty air filter and clean or replace.
				heating	Check fan motor operation and airflow restrictions.
					Dirty air coil — construction dust, etc. Perform preventative mainte-
					nance; Clean air coil.
					High external static. Check duct design and downstream interference.
		X		Air temperature out of range	Bring return-air temperature within design parameters.
				in heating
		X	X	Overcharged with refrigerant	Check superheat/subcooling vs. typical operating condition.
		X	X	Bad HP switch	Check switch continuity and operation. Replace.
LP Fault — Code 3		X	X	Insufficient charge	Check for refrigerant leaks.
Low Pressure/Loss of		X		Compressor pump down at	Check charge and start-up water flow.
Charge
				start-up
FP1 Fault — Code 4		X		Reduced or no water flow in	Check pump operation or water valve operation/setting.
Water Freeze Protection				heating
					Plugged strainer or filter. Clean or replace.
					Check water flow adjust to proper flow rate.
		X		Inadequate antifreeze level	Check antifreeze density with hydrometer.
		X		Improper freeze protect set-	Clip JW3 jumper for antifreeze (–12.2 C) use.
				ting (–1.1 C vs –12.2 C)
		X		Water temperature out of	Bring water temperature within design parameters.
				range
		X	X	Bad thermistor	Check temperature and impedance correlation.
FP2 Fault — Code 5			X	Reduced or no airflow in	Check for dirty air filter and clean or replace.
Air Coil Freeze				cooling	Check fan motor operation and airflow restrictions.
Protection
					High external static. Check duct design and downstream interference.
			X	Air temperature out of range	Too much cold vent air. Bring entering-air temperature within design
					parameters.
			X	Improper freeze protect set-	Normal airside applications will require –1.1 C only.
				ting (–1.1 C vs –12.2 C)
		X	X	Bad thermistor	Check temperature and impedance correlation.
Condensate Fault —		X	X	Blocked drain	Check for blockage and clean drain.
Code 6		X	X	Improper trap	Check trap dimensions and location ahead of vent.
			X	Poor drainage	Check for piping slope away from unit.
					Check slope of unit toward outlet.
					Poor venting. Check vent location.
			X	Moisture on sensor	Check for moisture shorting to air coil.
Over/Under Voltage —		X	X	Under voltage	Check power supply and 24-vac voltage before and during operation.
Code 7					Check power supply wire size.
(Auto Resetting)
					Check compressor starting.
					Check 24-vac and unit transformer tap for correct power supply voltage.
		X	X	Over voltage	Check power supply voltage and 24 vac before and during operation.
					Check 24-vac and unit transformer tap for correct power supply voltage.
Performance Monitor —		X		Heating mode FP2> 51.7 C	Check for poor airflow or overcharged unit.
Code 8			X	Cooling mode FP1> 51.7 C	Check for poor water flow or airflow.
				OR FP2< 4.4 C
No Fault Code Shown		X	X	Compressor overload	Check and replace if necessary.
		X	X	Control board	Reset power and check operation.
Unit Short Cycles		X	X	Dirty air filter	Check and clean air filter.
		X	X	Unit in Test mode	Reset power or wait 20 minutes for auto exit.
		X	X	Unit selection	Unit may be oversized for space. Check sizing for actual load of space.
		X	X	Compressor overload	Check and replace if necessary.
Only Fan Runs		X	X	Thermostat position	Ensure thermostat set for heating or cooling operation.
		X	X	Unit locked out	Check for lockout codes. Reset power.
		X	X	Compressor overload	Check compressor overload. Replace if necessary.
		X	X	Thermostat wiring	Check Y and W wiring at heat pump. Jumper Y and R for compressor
					operation in Test mode.
	LEGEND
FP	— Freeze Protection
HP	— High Pressure
LED — Light-Emitting Diode
LP	— Low Pressure
RV	— Reversing Valve

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