Constant circulation noise, no leaks help please

[emmgemuk]

Hi I am hoping I can draw on your experiences to fix my central heating problem.
We have an 18 month old saunier duval f 30 e combi.
We have been hearing a water circulating noise from our pipes which serve the taps ,for about a week, when the heating was off and there were no taps running. Yesterday we awoke to a cold house, after some fiddling with the boiler (ie turning it off and on again) it eventually fired up, only to cut out again within seconds. There is no error code displayed and the pressure is steady at 1.1 bar which I believe means there is no leak in the radiator system.
I did get it to come on twice yesterday, but it only stayed on for about an hour before cutting out, the hot water was instant.
Concerned that our turning it on and off again wasnt doing it any good I turned it off. We could still hear a water circulating noise and when I checked the water meter it was whirling like mad, so I turned the stopcock off and this stopped. Indicating that there is no leak between the supply and the stopcock.
We have scoured all around the house and there is no leak. The overflow is bone dry.
Our plumber is away, and I am hoping that someone will have an idea of what the problem is so that we can explain it to a plumber thus cutting down on his labour time!!!
Many thanks in advance

 

[JohnD]

Can you identify the filling loop on the boiler?

do you have radiator or other pipes under the floor?

 

[emmgemuk]

Many thanks for replying
Yes I have traced the filling loop, from the stoptap to the boiler and out again, and followed it all around the house.
There are radiator pipes under the floors, however the circulating noise isnt coming from those pipes, it the ones that lead to the upstairs taps.
There are no patches anywhere on ceillings or floors, and from looking at the meter the amount of water that was going in there would be big eveidence by now. Would a valve inside the boiler be stuck on causing it to contstantly pull water through?

 

[JohnD]

the filling loop is (usually) a flexible piece of hose with a braided steel cover, with a valve at each end. It is used to pressurise the boiler, and carries water at mains pressure. Have another look.

It is supposed to be turned off and disconnected when the boiler is not being topped-up. If it is left connected and turned on, or even leaking slightly, it can cause excessive water pressure inside the radiator pipes, and maybe a burst or leak.

I assume you have no pipes or tanks in the loft.