E16
Alpha
External Control / Thermostat Fault
Boiler displays E16; may occur when external controls are calling for heat.
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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
Incorrect room thermostat wiring, Faulty external programmer, Shorted control terminals, Open-circuit demand signal
How to Fix / Troubleshooting
Safety: Turn off power before working on control wiring.
- Check control settings: Ensure the room thermostat and programmer are set to call for heat and that any batteries are fresh.
- Inspect wiring at boiler: Remove the boiler's lower cover to access the control terminal block. Verify that external controls are wired according to the Alpha wiring diagram.
- Bypass test (qualified person): Temporarily link the boiler's room thermostat terminals to simulate a call for heat. If the boiler runs without E16, the external controls or wiring are faulty.
- Correct polarity: Ensure live and neutral are correctly connected at the boiler supply; incorrect polarity can cause control errors.
Persistent E16 may require an electrician or heating engineer to rewire or replace external controls.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat / External Controls
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