WORCESTER BOSH GREENSTAR 28i JUNIOR

[sourcebranch]

I have come across two banging problems on these.

1. resonating external bypass valve. Obviously this would not happen if the heating was off.

The other one, which alot of people are mentioning was the expansion vessel but not the usual problem!!! I have come across this on two seperate boilers.
LOOSE EXPANSION VESSEL.

On the worcester, the vessel just sits in the back. What I found was the vessel was intermitantly vibrating. Which was causing a few different noises including humming.

This also happened at night whilst the boiler fired up on preheat.

The way I cured this was to push the vessel over to the side so it would wedged itself. I have not been called back to either of them.

Hopefully this is of use to you.

 

[MARTIN927]

I have given up, the worcester engineer doesn't know, the water board engineer doesn't know, the men who fitted the boiler have been back and checked everything, they don't know what the dull thud is.
I will take a look at the expansion vessel as recommended by 'sourcebranch' if that doesn't work there is only one thing left to do - move house or buy ear plugs..
Thanks everyone for your contributions.