Buderus
Unwanted Heating / Valve Bypass
Radiators get hot even when there is no call for heating
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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
Stuck open diverter valve (on combi), Faulty motorized zone valve, Incorrect wiring causing permanent call for heat, Internal leak between heating and DHW circuits
How to Fix / Troubleshooting
Safety: Allow radiators to cool before working on valves.
- 1. Check controls: Ensure the room thermostat and programmer are not calling for heat and that any manual override switches are off.
- 2. Feel pipes: If the flow pipe from the Buderus boiler is hot when there is no demand, the boiler may be receiving a false call for heat.
- 3. Zone valves: Check motorized valves; if the manual lever is stuck in the open position, reset it. Replace faulty actuators.
- 4. Diverter valve (combi): On combi models, a stuck diverter valve can send heat to radiators during DHW demand. The valve assembly may need cleaning or replacement.
- 5. Wiring check: Verify that external controls are wired correctly and not permanently bridging the demand terminals.
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Repair Difficulty
Medium
3/5
Required Part
Diverter Valve / Motorized Zone Valve
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