Worcester Bosch
Heating Circuit Flow Problem
Boiler runs but radiators do not get hot, hot water is available on a combi or system boiler.
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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 motorised zone valve, Airlock in heating circuit, Blocked system filter, Pump not circulating to radiators
How to Fix / Troubleshooting
Safety first: Turn off power before working on valves or pump. System water may be hot.
User checks:
- Ensure room thermostat and programmer are calling for heat.
- Check that radiator valves are open.
Engineer actions:
- Check operation of motorised zone valves (e.g., Honeywell or Worcester-branded) and replace heads or valves if stuck.
- Bleed air from radiators and high points in the system.
- Inspect and clean any system filter installed on the return to the boiler.
- Verify pump is circulating water through the heating circuit and not just through a bypass.
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Repair Difficulty
Medium
3/5
Required Part
Motorised Zone Valve
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