H11
Worcester Bosch
Flow Switch / DHW Demand Detection Fault
Boiler shows H11, may not respond to hot water demand or may give priority issues.
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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 or turbine, Blocked inlet filter, Wiring fault to flow sensor
How to Fix / Troubleshooting
Safety first: Isolate power and water. Be prepared for water spillage when removing sensors.
Engineer actions:
- Check the DHW flow sensor/turbine for free movement and clean any debris.
- Inspect and clean the cold water inlet filter to the boiler.
- Test the sensor output (pulse or resistance) during water flow and compare with specifications.
- Replace the DHW flow sensor if faulty.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor
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