Bosch
No Domestic Hot Water on Combi Boiler
Boiler heats radiators but does not provide hot water on a combi model.
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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
Faulty DHW flow sensor/turbine, Stuck diverter valve not moving to DHW position, Blocked plate heat exchanger, DHW NTC sensor fault
How to Fix / Troubleshooting
Safety: Turn off power and isolate cold water supply before removing any water components.
Steps:
- Check that the boiler is not in heating‑only mode and that DHW is enabled.
- Open a hot tap fully and observe the boiler: does it register a DHW demand on the display? If not, the DHW flow sensor may be faulty.
- If the boiler fires but water remains lukewarm, the plate heat exchanger may be scaled and require professional descaling or replacement.
- If CH works but DHW does not and the boiler shows DHW demand, the diverter valve may be stuck and needs servicing.
Flow sensor, plate heat exchanger, and diverter valve work should be done by a qualified engineer.
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Repair Difficulty
Hard
4/5
Required Part
DHW Flow Sensor / Diverter Valve / Plate Heat Exchanger
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