EHC
Inconsistent DHW Temperature Control
Boiler hot water temperature fluctuates between very hot and cold during a shower.
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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
Scaled plate heat exchanger, Faulty DHW NTC sensor, Unstable DHW flow rate, Diverter valve modulation issue
How to Fix / Troubleshooting
Safety: Risk of scalding from sudden hot water surges. Use caution.
User checks:
- Ensure shower mixer is suitable for combi boilers and not restricting flow excessively.
- Run the hot tap fully open to stabilise flow and see if temperature improves.
Engineer checks:
- Descale or replace the plate heat exchanger on the EHC combi boiler.
- Check DHW NTC sensor readings and replace if unstable.
- Verify DHW flow sensor operation and that minimum flow rate is achieved.
- Inspect diverter valve for smooth modulation.
Stable flow and clean heat exchange surfaces are key to consistent hot water temperature.
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Repair Difficulty
Hard
4/5
Required Part
Plate Heat Exchanger
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