Pentair UltraTemp Heat Pump Troubleshooting Guide
The Pentair UltraTemp is a high-efficiency heat pump designed for pool and spa heating. Like all heat pumps, it has a sophisticated control system that monitors operations and displays alarm codes when issues are detected.
This guide covers all UltraTemp alarm codes and common troubleshooting scenarios to help pool service professionals diagnose and resolve issues in the field.
Understanding the Control Panel
The UltraTemp features a digital control panel with:
- LCD Display: Shows temperature, mode, and alarm messages
- Power LED (Green): Indicates unit is powered on
- Service LED (Red): Lit when an alarm condition exists
- ON/OFF Button: Powers the heat pump on/off and clears alarms
UltraTemp Alarm Codes
Temperature Sensor Alarms
HIGH WATER TEMP
Water temperature is above 108F (42.2C).
Causes: Bad thermistor or control board malfunction
Solution: Test actual water temperature. Use 10K ohm resistance test to verify thermistor. Replace thermistor if bad, or control board if thermistor tests good.
LOW WATER TEMP
Water temperature is below 40F (4.4C).
Causes: Bad thermistor, control board, or debris shorting connections
Solution: Test actual water temperature. Use 10K ohm resistance test to verify thermistor. Remove debris or replace components as needed.
WATER THERM SHORT
Water temperature sensor circuit is shorted.
Solution: Use 10K ohm resistance test. If shorted, replace thermistor. If good, replace control board.
WATER THERM OPEN
Water temperature sensor circuit is open.
Solution: Use 10K ohm resistance test. If open, replace thermistor. If good, replace control board.
SUCTION TH SHORT
Defrost refrigerant temperature sensor circuit is shorted.
Solution: Use 10K ohm resistance test. If shorted, replace thermistor. If good, replace control board.
SUCTION TH OPEN
Defrost refrigerant temperature sensor circuit is open.
Solution: Use 10K ohm resistance test. If open, replace thermistor. If good, replace control board.
Flow and Pressure Alarms
LOW WATER FLOW
The pressure switch sensing water flow is open.
Common Causes:
- Water circulation pump not on
- Insufficient water flow (dirty filter, clogged skimmers)
- External bypass valve open
- Bad water pressure switch
Solution: Verify pump is running, clean filters, close bypass valves, and test pressure switch with water flowing.
HIGH REFRIG
Refrigerant high pressure switch is open.
Common Causes:
- Insufficient water flow through heat exchanger
- External bypass open
- Bad refrigerant high pressure switch
- TXV stuck closed
- Unit overcharged
- Compressor thermal protector tripped
Solution: Check water flow, verify bypass closed, test pressure switch. May require HVAC technician for refrigerant issues.
LOW REFRIG
Refrigerant low pressure switch is open.
Common Causes:
- Low refrigerant (leak)
- Air/water temperatures too cold
- Bad refrigerant low pressure switch
- Faulty fan motor or capacitor
- TXV stuck closed
- Insufficient airflow through coil
Solution: Check for leaks, verify fan operation, clear debris from coil. May require HVAC technician.
Electrical Alarms
BROWNOUT
The 24 VAC supply voltage to the control board is low.
Causes: Bad transformer or insufficient supply voltage
Solution: Check supply voltage (should be 208-260V). Transformer should output 24-28V. A boost transformer may be needed.
Other Alarms
REMOTE POOL SPA
Pool and Spa remote inputs are simultaneously energized.
Solution: Modify automation control output so only pool/common OR spa/common terminals are energized, not both.
LOW AMBIENT TEMP
Air temperature is too low for heat pump operation. Defrost cycle did not complete within allotted time.
Solution: Wait until ice melts from evaporator coil and air temperatures rise. Check suction thermistor with 10K ohm test.
FIVE ALARMS
Indicates 5 faults have occurred within 1 hour. This alarm automatically resets in one hour or can be manually reset.
Solution: Press ON/OFF button to clear. Monitor heat pump to identify which alarm is recurring.