Hayward HeatPro Troubleshooting Guide
The Hayward HeatPro is a titanium heat exchanger heat pump covering models HP20654T through HP21104TC and related variants. It runs on R-410A refrigerant and operates on 240V AC. This guide covers every common error code and failure mode a pool service technician will encounter in the field, with direct links to step-by-step articles for each problem.
Safety First
HeatPro units operate on 240V AC and contain R-410A refrigerant under pressure. Only trained, EPA-certified technicians should diagnose refrigerant-side faults or open the electrical panel. Always disconnect power at the breaker before touching internal components. Contact Hayward Technical Service at 908-355-7995 for factory support.
Quick Reference: Error Codes
LP — Low Pressure
The low pressure switch has opened because refrigerant pressure dropped below 80 PSI. Most commonly caused by a refrigerant leak. Auto-resets at 120 PSI.
Diagnose LP ErrorHI / HP — High Pressure
The high pressure switch opened because discharge pressure exceeded 590 PSI. Restricted water flow is the most common cause. Auto-resets at 440 PSI.
Diagnose HI/HP ErrorPO / OP — Open Water Temp Sensor
The water temperature sensor circuit is open (infinite resistance). The HeatPro uses a 10k ohm sensor. Check wiring and sensor resistance against the temp/resistance chart.
Diagnose PO/OP ErrorFlo / PS — No Flow
The water pressure switch is open, indicating no or low water flow through the heat exchanger. Pump off, dirty filter, or closed bypass valve are the most common causes.
Diagnose Flo/PS ErrorPc / SH — Shorted Water Temp Sensor
The water temperature sensor circuit is shorted (near-zero resistance). Same 10k ohm sensor as PO/OP. Check for shorted wires or damaged sensor before replacing the control board.
Diagnose Pc/SH ErrorFs / dEF — Freeze / Defrost
The heat pump is in defrost mode. Normal when ambient temps are in the mid-50s or below. Abnormal defrost in warm weather indicates a failing defrost temperature sensor.
Diagnose Fs/dEFBlank Display — No Power
No low voltage reaching the control board. A tripped breaker or blown 1-amp fuse on the HeatPro interface board is the most common cause.
Diagnose Blank DisplayNot Heating / Slow Heat Gain
Heat pump runs but pool temperature does not rise. Covers ambient temperature limits, undersized units, low refrigerant, and air temperature differential diagnostics.
Diagnose Heating ProblemsHow the HeatPro Works
The HeatPro is a vapor-compression heat pump. The fan pulls ambient air across the evaporator coil, where R-410A refrigerant absorbs heat from the air and vaporizes. The compressor pressurizes the refrigerant vapor, which flows through the titanium heat exchanger where it transfers heat to the pool water. The refrigerant then expands through the TXV and the cycle repeats.
Normal low-side pressure is 125–135 PSI. Normal high-side pressure is 290–400 PSI. Normal air temperature differential across the coil is 15–20°F. These three readings are your baseline for any refrigerant-side diagnosis.
The heat pump has a built-in 5-minute delay on startup — no operation will occur during this period. This is intentional and protects the compressor from short cycling. The same delay applies any time power is interrupted.
Before You Diagnose: Check These First
- Is the pool pump running? The HeatPro will not operate when the pool pump is off. Confirm pump is running and filter is clean before diagnosing any error code.
- Is the thermostat set above water temp? The unit will not call for heat if the setpoint equals or is below the current pool temperature.
- Is the 5-minute startup delay still active? After power restoration or a trip event, wait at least 5 minutes before diagnosing a no-heat complaint.
- Is the unit in remote/standby mode? If a ProLogic or other automation is connected, the unit must be in standby mode (three scrolling dots) for remote control to work.
Normal Condensation vs. Refrigerant Leak
HeatPro units produce 3–5 gallons of condensation per hour in humid conditions — this is normal and not a leak. To distinguish condensation from a refrigerant-induced water leak: condensation will stop within a few hours of the unit shutting off, while a true leak continues when the unit is not running. Test suspect water with a chlorine strip — pool water will show measurable chlorine; condensation will not.