11
TROUBLE SHOOTING ANALYSIS TABLE
COMPLAINT
PROBABLE CAUSE
REMEDY
1. High Head Pressure
1. Excessive charge of refrigerant in system.
2. Inadequate supply of air across the
condenser coil.
3. Non-condensate gases in the system.
1. Purge or pump-down excessive charge.
2. Make certain that coil is not fouled in any
way, or that air is not re-circulating.
3. Purge these gases from the system.
Recharge system, if necessary.
2. Low Head Pressure
1. System low on refrigerant.
2. Compressor valves broken.
1. Charge system until sight glass is clear of bubbles.
2. Replace compressor.
3. Low Suction Pressure
1. Liquid line valve closed.
2. Restricted liquid line.
3. The bulb of the thermal expansion valve
has lost its charge.
4. System low on refrigerant.
5. Dirty filters.
6. Coil frosted up.
7. Flash gas in the liquid line.
8. Quantity of air through evaporator not
adequate.
1. Open the liquid line valve.
2. Replace filter-dryer.
3. Detach the bulb from the suction line and hold
in one hand. If no liquid refrigerant goes through
the valve, replace the valve.
4. Test the unit for leaks. Add refrigerant until sight
glass is free from bubbles, after repairing leak.
5. Clean or replace filter.
6. Defrost and clean coil. Clean or replace filters.
7. Excessive liquid line drop. Check liquid line size.
8. Increase the blower speed.
4. High Suction Pressure
1. Expansion valve stuck open.
2. Expansion valve bulb not in contact with
suction line.
3. Suction and/or discharge valve leaking or
broken.
1. Correct valve action or replace the valve.
2. Fasten bulb securely to suction line.
3. Replace compressor.
5. Compressor will not
start.
1. Disconnect switch open.
2. Blow fuse or fuse at disconnect switch.
3. Thermostat set too high.
4. Selector switch in "Off" position.
5. Contactor and/or relay coils burned out.
6. Loose or open electrical connection in either
the control or power circuit.
1. Close the disconnect switch.
2. Check the cause of failure and replace the fuse.
3. Adjust to lower temperature.
4. Turn selector switch knob to "Cool" position.
5. Replace contactor and/or relay.
6. Inspect and secure all electrical connections.
The following information is intended for qualified service companies only.
Common causes for unsatisfactory operation of heat pumps in the heating mode include:
Dirty Filters
Dirty filters or inadequate airflow through the indoor coil. Failure
to keep clean filters and adequate airflow (375-425 CFM/ton) will
cause excessive discharge pressures that may cause the high-
pressure switch to function.
Low Return Air Temperatures
Return ductwork temperatures that are less than 60°F will cause
low discharge pressure, low suction pressure and excessive
defrost cycling.
Undercharging
An undercharged system will cause low discharge pressure, low
suction pressure and an accumulation of frost on the lower section
of the outdoor coil.
Poor Termination of Defrost
The defrost sensor must make good contact with the outside coil
return bend or a non-termination of defrost may occur.
Reversing Valve
A reversing valve may not function correctly for the following
reasons:
1.
Solenoid does not energize when voltage is present
Replace the reversing valve.
2.
No voltage to the solenoid
Check the wiring.
3.
The valve will not shift
a. Undercharged
Check for leaks
b. Valve body damage
Replace the reversing valve
c. Valve sticking
Replace the reversing valve
TROUBLESHOOTING ANALYSIS TABLE - COOLING
TROUBLESHOOTING ANALYSIS - HEATING