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Table 39 — WSHP Troubleshooting (cont)
LEGEND
FAULT HEATING COOLING POSSIBLE CAUSE SOLUTION
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 performance per
Tables 11-13.
X Reduced or no water flow in cool-
ing
Check pump operation or valve operation/setting.
Check water flow adjust to proper flow rate. See Tables 19 and 31.
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 condenser cleaning.
X X Unit overcharged Check superheat and subcooling. Reweigh in charge.
X X Noncondensables in system Remove refrigerant, evacuate system and charge unit.
X X Restricted metering device Check superheat and subcooling per Tables 20-30. 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 performance per
Tables 11-13.
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
Temperature in Heating
X Too high airflow Check blower performance per Tables 11-13.
X Poor performance See “Insufficient Capacity.”
High Humidity X Too high airflow Check blower performance per Tables 11-13.
X Unit oversized Recheck loads and sizing check sensible cooling load and heat pump
capacity.
Low Refrigerant Suction
Pressure
X Normal operation Check/compare with Tables 20-30.
X Reduced water flow Check pump operation.
Check strainer or filter.
Improper flow regulator. Replace flow regulator.
X Water temperature out of range Bring water temperature within proper range.
X Scaling in water to refrigerant
heat exchanger
Conduct water quality analysis.
X Reduced airflow Check for dirty air filter.
Check for dirty air coil.
Check fan motor operation.
External static pressure exceeds fan operating parameters.
X X Return air temperature below
minimum
Space temperature too cold. Increase space temperature.
Excessive fresh air. Reduce amount of fresh air exposure.
X Supply air bypassing to return
airstream (zone systems)
Check for leaking ductwork.
X X Insufficient refrigerant charge Locate and repair leak.
X X Improperly located TXV sens-
ing bulb
Locate bulb on suction line between reversing valve and compressor.
X X Failed or restricted metering
device
Failed TXV power head, capillary or sensing bulb. Replace.
Plugged TXV strainer. Unplug TXV strainer.
High Refrigerant
Superheat
X X Insufficient refrigerant charge Locate and repair leak.
X X Improperly located TXV sens-
ing bulb
Locate bulb on suction line between reversing valve and compressor.
X X Failed or restricted metering
device
Failed TXV power head, capillary or sensing bulb. Replace.
Plugged TXV strainer. Unplug TXV strainer.
High Refrigerant
Subcooling
X X Excessive refrigerant charge Remove refrigerant as needed.
X X Failed or restricted metering
device
Failed TXV power head, capillary or sensing bulb. Replace.
Plugged TXV strainer. Unplug TXV strainer.
TXV and/or Low Pressure
Tubing Frosting
X Normal operation May occur when entering water temperature is close to minimum.
X X Insufficient refrigerant charge Locate and repair leak.
X X Failed or restricted metering
device
Failed TXV power head, capillary or sensing bulb. Replace.
Plugged TXV strainer. Unplug TXV strainer.
Equalizer Line
Condensing or Frosting
X X Failed or restricted metering
device
Failed TXV power head, capillary or sensing bulb. Replace.
Plugged TXV strainer. Unplug TXV strainer.
LED — Light-Emitting Diode
RV — Reversing Valve
TXV — Thermostatic Expansion Valve