F20
Aquacomfort
Safety Circuit Open
F20 error; heater will not start and may indicate a safety chain problem.
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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
Open high limit switch, Open pressure/flow switch, Tripped manual reset safety, Broken safety wiring
How to Fix / Troubleshooting
Safety first: Disconnect power and gas. Never bypass safety devices to force the heater to run.
- Trace safety chain: Using the wiring diagram, identify all safety devices in series (high limits, pressure switch, flue sensor, etc.).
- Check each device: With power off, test continuity across each safety device. Any that read open when conditions are normal may be faulty or tripped.
- Reset manual devices: Some high limits or rollout switches have a manual reset button. After the heater has cooled and the cause is addressed, press to reset.
- Repair wiring: Repair or replace any broken or corroded wires in the safety circuit.
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Repair Difficulty
Hard
4/5
Required Part
High Limit Switch
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