Poolworld
Unintended Firing / Control Logic Fault
Heater turns on even when there is no call for heat from the pool controller
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Stuck relay on control board, Miswired external control, Shorted thermostat input, Faulty temperature sensor reading low
How to Fix / Troubleshooting
Safety first: Turn OFF power and gas if the heater is firing unexpectedly.
- Verify setpoint: Check that the set temperature is not inadvertently set very high and that the mode is correct.
- Disconnect external control: Temporarily disconnect any external thermostat or automation wires and see if the issue persists when using only the local controls.
- Check sensor readings: Compare displayed water temperature to an external thermometer. If the heater thinks the water is much colder than it is, the sensor may be faulty.
- Inspect control board: If the heater still fires with no call for heat, the main control board relay may be stuck and should be replaced.
Warning: Unintended firing is a serious safety issue; do not leave the heater powered until the cause is corrected.
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Repair Difficulty
Hard
4/5
Required Part
Main Control Board
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