E20
Main
Air Pressure Switch Stuck or Out of Range
Boiler shows E20, fan may run but ignition does not occur
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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
Failed air pressure switch, Blocked sensing tubes, Incorrect flue installation, Fan not achieving required speed
How to Fix / Troubleshooting
Safety: Flue and combustion safety components must be serviced by a competent engineer. Isolate power and gas.
- Check flue terminal: Ensure the Main flue outlet is not obstructed and that any plume management kit is correctly fitted.
- Engineer checks:
- Inspect and clear silicone tubes between the fan/venturi and air pressure switch.
- Test the air pressure switch operation with a manometer and multimeter.
- Verify fan speed and replace the Main fan or air pressure switch as required.
- Confirm flue length and configuration are within Main’s specified limits.
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Repair Difficulty
Professional Required
5/5
Required Part
Air Pressure Switch
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