Heat Controller A-13 Symptom, Possible Cause, Remedy, Cooling Trouble Shooting Chart

COOLING TROUBLE SHOOTING CHART

!WARNING

DISCONNECT ALL POWER TO UNIT BEFORE SERVICING. CONTACTOR MAY BREAK ONLY ONE SIDE. FAILURE TO SHUT OFF POWER CAN CAUSE ELECTRICAL SHOCK RESULTING IN PERSONAL INJURY OR DEATH.

SYMPTOM		POSSIBLE CAUSE		REMEDY
Unit will not run	•	Power off or loose electrical connection	• Check for correct voltage at compressor contactor in control
				box
	• Thermostat out of calibration-set too high		•	Reset
	•	Failed contactor	• Check for 24 volts at contactor coil - replace if contacts are
				open
	•	Blown fuses	•	Replace fuses
	•	Transformer defective	•	Check wiring-replace transformer
	• High pressure control open (if provided)		• Reset-also see high head pressure remedy-The high pressure
				control opens at 610 PSIG
	• Interconnecting low voltage wiring damaged		•	Replace thermostat wiring
Condenser fan runs, compressor	•	Run or start capacitor failed (single phase only)	•	Replace
doesn’t	•	Start relay defective 9single phase only)	•	Replace
	•	Loose connection	• Check for correct voltage at compressor -
				check & tighten all connections
	• Compressor stuck, grounded or open motor winding		• Wait at least 2 hours for overload to reset.
		open internal overload.		If still open, replace the compressor.
	•	Low voltage condition		At compressor terminals, voltage must be within 10% of rating
				plate volts when unit is operating.
	•	Low voltage condition	• Add start kit components
Insufficient cooling	•	Improperly sized unit	•	Recalculate load
	•	Improper airflow	• Check - should be approximately 400 CFM per ton.
	•	Incorrect refrigerant charge	• Charge per procedure attached to unit service panel.
	• Air, non-condensibles or moisture in system		• Recover refrigerant, evacuate & recharge, add filter drier
	•	Incorrect voltage	• At compressor terminals, voltage must be within 10% of rating
				plate volts when unit is operating.
Compressor short cycles	•	Incorrect voltage	• At compressor terminals, voltage must be ± 10% of
				nameplate marking when unit is operating.
	•	Defective overload protector	• Replace - check for correct voltage
	•	Refrigerant undercharge	•	Add refrigerant
Registers sweat	•	Low evaporator airflow	• Increase speed of blower or reduce restriction - replace air
				filter
High head-low vapor pressures	•	Restriction in liquid line, expansion device or filter drier	• Remove or replace defective component
	• Flow check piston size too small		• Change to correct size piston
	•	Incorrect capillary tubes	•	Change coil assembly
	• TXV does not open		•	Replace TXV
High head-high or normal vapor	•	Dirty condenser coil	•	Clean coil
pressure - Cooling mode	•	Refrigerant overcharge	•	Correct system charge
	• Condenser fan not running		•	Repair or replace
	• Air or non-condensibles in system		• Recover refrigerant, evacuate & recharge
Low head-high vapor pressures	•	Defective Compressor valves	•	Replace compressor
	•	Incorrect capillary tubes	•	Replace coil assembly
Low vapor - cool compressor -	•	Low evaporator airflow	• Increase speed of blower or reduce restriction - replace air
iced evaporator coil				filter
	• Operating below 65°F outdoors		• Add Low Ambient Kit
	•	Moisture in system	• Recover refrigerant - evacuate & recharge - add filter drier
High vapor pressure	•	Excessive load	•	Recheck load calculation
	•	Defective compressor	•	Replace
Fluctuating head & vapor	•	TXV hunting	• Check TXV bulb clamp - check air distribution on coil - replace
pressures				TXV
	• Air or non-condensibles in system		• Recover refrigerant, evacuate & recharge
Gurgle or pulsing noise at	•	Air or non-condensibles in system	• Recover refrigerant, evacuate & recharge
expansion device or liquid line
Circulating air blower & inducer	•	Manual reset overtemperature control	•	Reset or replace
run continuously,	•	tripped
compressor will not start	•	Wire loose in limit circuit	•	Check wiring

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