Worcester Bosch Inconsistent DHW Temperature Control

Hot water temperature fluctuates, running hot then cold, especially at low flow rates.

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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 flow turbine, Gas valve modulation issues

How to Fix / Troubleshooting

Safety first: Water may become very hot unexpectedly; test with care.

  • Run tap fully: Open the hot tap fully to ensure adequate flow through the boiler; very low flow can cause cycling.
  • Check cold mains: Ensure cold water pressure is stable and other outlets are not being used heavily at the same time.
  • Engineer tasks: An engineer should check DHW sensor readings, clean or replace the plate heat exchanger, inspect the flow turbine, and verify gas valve modulation.
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Repair Difficulty

Hard 4/5

Required Part

Plate Heat Exchanger (DHW)
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