Worcester boiler 28cdi banging noise.

23 Nov 2011
Reaction score
United Kingdom
When operating hot tap banging noise coming from boiler, it's an intermittent fault. Investigations to possible problem diverter valve check operation ok, plate to plate heat exchanger removed, cleaned & refit. Gas to water heat exchanger removed & refit checked out ok. Checked continuity of wiring to DWH & CH found to be ok, checked gas inlet pressure 21.5 m/bar to 22 m/bar. Burner pressure 15 m/bar should be 15.5 m/bar, tried to adjust unresponsive.
Followed domestic hot water procedure, mode switch minimum setting no response, no drop in pressure, maintained 15 m/bar with tap running. Boiler cycles CH off 2 min 25 secs on 41 secs.
Any ideas, any Worcester experts out there - any help appreciated?
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Water is clear throughout the system DHW & CH no contamination either side, heat exchanger intact.
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Think'n back I remember the pump get'n excessively hot,so I switch off the boiler,then after afew minutes switched it back on,the pump ran and the tempreture came down to normal about 60c.

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