11
Biasi
Room Thermostat / External Control Fault
Boiler shows error 11, no response to thermostat, display may be normal but no heating demand is recognised.
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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 circuit in room thermostat wiring, Faulty external programmer, Incorrect wiring at boiler control terminals, PCB input fault
How to Fix / Troubleshooting
Safety: Isolate power before accessing the wiring compartment.
- Check controls: Ensure the room thermostat is turned up above room temperature and that any external programmer is calling for heat.
- Inspect wiring: Remove the boiler's lower cover to access the control terminal strip. Check that the thermostat or link wire is correctly connected to the Biasi demand terminals.
- Test with link (engineer): A competent person can temporarily fit a link wire across the demand terminals to simulate a call for heat. If the boiler then fires, the external controls or wiring are at fault.
- Replace faulty control: If the thermostat or programmer is defective, replace with a compatible control following Biasi wiring diagrams.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat
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