Worcester Bosch
Plate Heat Exchanger Partially Blocked
Intermittent hot water temperature: water runs hot then cold on a Worcester Bosch combi.
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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
Limescale build-up in plate heat exchanger, Sludge contamination from heating circuit, Faulty DHW temperature sensor
How to Fix / Troubleshooting
Safety first: Isolate power and water. Surfaces and water may be hot; allow to cool.
User actions:
- Check that cold water inlet pressure is stable and that all isolation valves are fully open.
Engineer actions:
- Isolate and remove the plate heat exchanger from the boiler.
- Visually inspect for scale and sludge; chemically descale using an appropriate descaling solution or replace the exchanger if heavily fouled.
- Flush the heating system and fit an in-line magnetic filter to prevent recurrence.
- Check the DHW NTC sensor for correct operation and replace if necessary.
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Repair Difficulty
Hard
4/5
Required Part
Plate Heat Exchanger
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