Keston
Inadequate or Unstable Domestic Hot Water
Boiler fires but hot water temperature at taps is poor or fluctuates
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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, Partially blocked DHW filter, Diverter valve not fully moving to DHW position
How to Fix / Troubleshooting
Safety: Risk of scalding if temperature suddenly increases. Test water carefully before use.
User actions:
- Open hot taps fully rather than trickling to stabilise flow.
- Avoid running multiple hot outlets simultaneously if the boiler is small relative to demand.
- If temperature swings are severe, stop using hot water from the boiler and call an engineer.
Engineer actions:
- Check DHW flow rate and compare with Keston specifications.
- Clean the DHW inlet filter and descale or replace the plate heat exchanger if restricted.
- Verify correct operation of the diverter valve and replace if it does not fully travel to DHW position.
- Test the DHW NTC sensor and wiring for accurate temperature feedback.
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Repair Difficulty
Medium
3/5
Required Part
Plate Heat Exchanger
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