E17
Main
Flow Switch or Turbine Fault (DHW Flow Detection)
Boiler intermittently shows E17, especially during hot water use with combi models
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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
Sticking DHW flow switch, Blocked flow turbine, Limescale in DHW inlet, Faulty flow sensor wiring
How to Fix / Troubleshooting
Safety: Isolate power and close cold water inlet before removing any DHW components. Water may be under pressure.
- Check DHW flow: Open a hot tap fully and confirm that water flow is strong. Weak flow may indicate a blocked inlet filter or scale.
- Clean inlet filter: Many Main combi boilers have a filter on the cold inlet. Isolate the cold feed, remove the filter, and rinse debris.
- Engineer checks:
- Inspect and clean the DHW flow turbine or paddle switch inside the Main boiler.
- Test the flow sensor signal at the PCB while running a tap.
- Descale the DHW side of the plate heat exchanger if scale is suspected.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor
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