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Video - infrequent rumbling noise from WB combi boiler

View the thread, titled "Video - infrequent rumbling noise from WB combi boiler" which is posted in Boiler Advice Forum on UK Plumbers Forums.

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ph0u203d

Hi, as part of some building work last summer I had a Worcester Bosch Greenstar 37 CDI combi boiler (about 4 years old at the time) moved from one wall (since knocked down) to another in my kitchen. Ever since, but very infrequently (1-2 times every 2 weeks), it makes a loud rumbling noise that can be heard throughout the house. It sometimes last for a few seconds but other times continues until I turn on the hot water tap. See this video for an example from a few nights ago:

tinypic.com/r/241ul2v/9

It's definitely coming from the boiler and not radiator TRVs. When it does happen it tends to be between 10 and 11 pm. The wireless CH thermostat times off at 10 pm but I've noticed that the green burner light is on when the noise occurs. In fact for the first time a few nights ago I was next to the boiler when the noise occurred - I heard it fire up just before the noise started. It does also occur (although much less frequently) when the CH thermostat is timed on but the set room temperature has been reached. It's happened once or twice in the middle of the night too.

I've asked the fitter that moved the boiler to come and look at it, but from the video and description he didn't have any immediate ideas as to what could be causing the noise. I'm not planning to tinker with anything myself but I was wondering if the video and description rang any bells, or if anyone had any ideas that could explain the problem? This might help the fitter to make a diagnosis. If not I can arrange for a WB engineer to come and look at it.

Any help would be much appreciated.
 
i would say when was it last serviced? and worcester fixed price repair is very good
 
Can't play the video...

Is it the hot water pre-heat? That's the only reason the boiler would be firing with no demand etc
 
Has it had the mini expansion vessel fitted on the mains inlet? Perhaps it had one fitted and when they moved the boiler, they didn't fit it back on. Sounds like water hammer
 
Just to update... The fitter came round and ran a few tests. He noticed the supply pressure at the meter was a bit low. Transco came our and fitted a new regulator. In the 2 weeks since we haven't heard the rumbling noise. Happy days! And yes it already had a mini expansion vessel. Thanks for your suggestions.
 

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