Biasi
No Central Heating Output
Boiler produces hot water but central heating does not come on, even though 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
Room thermostat or programmer fault, Diverter valve stuck in DHW position, Pump not running, Motorised valve fault on system boilers
How to Fix / Troubleshooting
Safety: Isolate power before accessing wiring or valves.
- Check controls: Ensure the programmer is set to heating ON and the room thermostat is turned up.
- Feel CH flow pipe: If the boiler fires but the CH flow pipe remains cool, the diverter may not be sending water to the radiators.
- Inspect external valves (system boilers): For Biasi system boilers with external motorised valves, check that the CH valve is opening when there is a call for heat.
- Engineer repair: A technician can test control circuits, replace faulty thermostats or valves, and service the diverter valve or pump.
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Repair Difficulty
Medium
3/5
Required Part
Room Thermostat
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