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FAULT
POSSIBLE CAUSE
Power Supply Off
Broken or Loose Wires
Voltage Supply Low
COMPRESSOR
DOES NOT
OPERATE
Safety Controls
Compressor Overload Open If the compressor is cool and the overload will not reset, replace compressor.
Compressor Motor
Compressor Windings Open
Discharge Pressure Too
UNIT OFF ON
HIGH-PRESSURE
SWITCH
Refrigerant Charge
High-pressure Switch
Suction Pressure Too Low
UNIT OFF ON
LOW-PRESSURE
SWITCH
Refrigerant Charge
Low-pressure Switch
Unit Oversized
UNIT SHORT
Wiring and Controls
CYCLES
Unit Undersized
Refrigerant Charge
INSUFFICIENT
Reversing Valve
COOLING OR
HEATING
Operating Pressures
Moisture, Noncondensables
Table 12 — Troubleshooting
Apply power, close disconnect.
Blown Fuse
Replace fuse or reset circuit breaker. Check for correct fuses.
Replace or tighten the wires. Check for loose or broken wires at compressor, capacitor, or
contactor..
If voltage is below minimum voltage specified on unit data plate, contact local power
company.
Set controller to "COOL" and lowest temperature setting, the unit should run in the cooling
mode (reversing valve energized). Set unit to "HEAT" and the highest temperature setting,
the unit should run in the heating mode. If the compressor does not run in all cases, the
Controller
controller could be miswired or faulty.To ensure miswired or faulty thermostat verify 24 volts
is available on the unit section low voltage terminal strip between "R" and "C," "Y" and "C,"
and "O" and "C." Replace the controller if defective.
Reset the controller to "OFF." After a few minutes turn to "COOL" or "HEAT." If the
compressor runs, unit was off on one of the safety controls. (See problem for possible
causes).
Internal winding grounded to the compressor shell. Replace compressor. If compressor
Grounded
burnout, install suction filter drier.
After compressor has cooled, check continuity of the compressor windings. If the windings
are open, replace the compressor.
In "COOLING" mode: SOURCE COIL - Lack of or inadequate water flow. Entering water
temperature too warm. Scaled or plugged condenser.
High
In "HEATING" mode: LOAD COIL - Lack of or inadequate water flow. Entering water
temperature too warm. Scaled or plugged load coil.
The unit is overcharged with refrigerant. Recover refrigerant, evacuate and recharge with
factory recommended charge.
Check for defective or improperly calibrated high-pressure switch.
In "COOLING" mode: LOAD COIL - Lack of or inadequate fluid flow. Entering water
temperature too cold. Scaled or plugged load coil.
In "HEATING" mode: SOURCE COIL - Lack of or inadequate fluid flow. Entering water
temperature too cold. Scaled or plugged source coil.
The unit is low on refrigerant. Check for refrigerant leak, repair, evacuate and recharge with
factory recommended charge.
Check for defective or improperly calibrated low-pressure switch.
Recalculate heating and or cooling loads.
Loose connections in the wiring or a defective compressor contactor.
Fluid Volume
Inadequate load side fluid volume.
Recalculate heating and or cooling loads. If excessive, possibly adding insulation and
shading will rectify the problem. Unit may be short of refrigerant.
Unit may be short on refrigerant charge.
Check for defective compressor. If discharge is too low and suction pressure is too high,
Compressor
compressor is not pumping properly. Replace compressor.
Defective reversing valve creating bypass of refrigerant from discharge to suction side of
compressor. Replace reversing valve.
Compare unit operating pressures to the pressure / temperature chart for the unit.
Check TXV (thermostatic expansion valve) for possible restriction or defect. Replace if
TXV
necessary.
The refrigerant system may be contaminated with moisture or noncondensables. Recover
refrigerant, evacuate and recharge with factory recommended charge. Note: a liquid line
drier may be required.
SOLUTION
39
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