30
Table 16 - Troubleshooting (cont’d)
Fault
Heating
Cooling
Possible cause
Solution
Only compressor runs
X
X
Thermostat wiring
Check G wiring at heat pump. Jumper G and R for fan operation.
X
X
Fan motor relay
Jumper G and R for fan operation. Check for line voltage across BR
contacts.
Check fan power enable relay operation (if present).
X
X
Fan motor
Check for line voltage at motor. Check capacitor.
X
X
Thermostat wiring
Check Y and W wiring at heat pump. Jumper Y and R for compressor
operation in Test mode.
Unit does not operate
X
Reversing valve
Set for cooling demand and check 24 V a.c. on RV coil and at control.
in cooling
If RV is stuck, run high pressure up by reducing water flow and while
operating, engage and disengage RV coil voltage to push valve.
X
Thermostat setup
Check for ‘O’ RV setup not ‘B’.
X
Thermostat wiring
Check O wiring at heat pump. Jumper O and R for RV coil ‘Click’.
Insufficient capacity/not
X
X
Dirty filter
Replace or clean.
cooling or heating properly
X
Reduced or no airflow in heating
Check for dirty air filter and clean or replace.
Check fan motor operation and airflow restrictions.
External static too high. Check blower Table 4.
X
Reduced or no airflow in cooling
Check for dirty air filter and clean or replace.
Check fan motor operation and airflow restrictions.
External static too high. Check blower Table 4.
X
X
Leaky ductwork
Check supply and return air temperatures at the unit and at distant duct
registers if significantly different, duct leaks are present.
X
X
Low refrigerant charge
Check superheat and subcooling Table 9.
X
X
Restricted metering device
Check superheat and subcooling Table 9. Replace.
X
Defective reversing valve
Perform RV touch test.
X
X
Thermostat improperly located
Check location and for air drafts behind thermostat.
X
X
Unit undersized
Recheck loads and sizing check sensible cooling load and heat pump
capacity.
X
X
Scaling in water heat exchanger
Perform scaling check and clean if necessary.
X
X
Inlet water too hot or cold
Check load, loop sizing, loop backfill, ground moisture.
High head pressure
X
Reduced or no airflow in heating
Check for dirty air filter and clean or replace.
Check fan motor operation and airflow restrictions.
External static too high. Check blower Table 4.
X
Reduced or no water flow in cooling
Check pump operation or valve operation/setting.
Check water flow; adjust to proper flow rate. See Table 8.
X
Inlet water too hot
Check load, loop sizing, loop backfill, ground moisture.
X
Air temperature out of range in heating
Bring return air temperature within design parameters.
X
Scaling in water heat exchanger
Perform scaling check and clean if necessary.
X
X
Unit overcharged
Check superheat and subcooling. Reweigh in charge.
X
X
Non-condensables in system
Vacuum system and reweigh in charge.
X
X
Restricted metering device
Check superheat and subcooling per Table 9. Replace.
Low suction pressure
X
Reduced water flow in heating
Check pump operation or water valve operation/setting.
Plugged strainer or filter. Clean or replace.
Check water flow adjust to proper flow rate.
X
Water temperature out of range
Bring water temperature within design parameters.
X
Reduced airflow in cooling
Check for dirty air filter and clean or replace.
Check fan motor operation and airflow restrictions.
External static too high. Check blower Table 4.
X
Air temperature out of range
Too much cold vent air. Bring entering air temperature within design
parameters.
X
X
Insufficient charge
Check for refrigerant leaks.
Low discharge air
X
Too high airflow
Check blower Table 4.
temperature in heating
X
Poor performance
See ‘Insufficient Capacity’.
High humidity
X
Too high airflow
Check blower Table 4.
X
Unit oversized
Recheck loads and sizing check sensible cooling load and heat pump
capacity.
Legend
RV - Reversing valve
