Noisy Combi Boiler

[hammersgirl]

For the last 3 weeks we have had buiders in to convert our en-suite into two en-suites. The plumber took some time running the new pipes for the shower, sink and toilet, mostly working evenings and weekends. Oh, and he had to remove a couple of radiators when walls were demolished. Obviously the (Vaillant) Combi Boiler and the water has been on and off repeatedly.
The heating is set to come on at 7am, but at 6.15 every morning there is a loud clunk and a repeated banging noise coming from somewhere round the boiler. My husband leaps out of bed to see if he can locate the precise location but no lluck so far. Does anyone know what could cause the noise when no-one is using the water at that time, and the heating has been off since 10pm? The noise does not happen at any other time.
Thanks

[matt1e]

sounds like "water hammer"
could be either trapped air in the system
or poorly clipped pipes
but then I'm a sparky and there are people on here more qualified than I am to advise you

[LibsW]

This sounds like something that happened with my combi which made similar noises to the ones you describe when it was either firing up the heating or the hot water. I got an engineer in who could tell just from looking at it that the burner had gone (i.e. it should look like a rectangular metal plate with tiny holes in but in firing it up the boiler had blown several large holes in it, which is what the banging noise was!). I would suggest getting someone in to take a look and perhaps give it a service at the same time, or wearing ear plugs!

[gucciman]

what model of vaillant is it

it could be that your boiler has a pre-heat on the water i.e. it fires up to pre-warm the water so when you turn a tap on you get hot water quicker
it does sound as though the problem could be air related or it could be the water in the heat exchanger boiling due to poor water circulation.
when your hubby checks the boiler is the burner on?