Hi,
Its been a long time since I have posted here, I have had British Gas down allot, trying to figure this out and for the moment they can't.
They thought pumping over at first, but changed the circulation pump on the boiler circuit (not the radiator circuit) and checked again and with further investigation it appears the dripping is not actually linked with the boiler or pumps running at all!!
As a test I ran both hot water and/or the radiator circuit to lower the temp in the tank. I tried both seperately, and both together. I also turned the tank thermostat down so the boiler did not kick in.
What happens is basically the tank drops temperature, and when its dropped a bit, usually over 10 degrees c the dripping will start. Its as though when the tank cools there is new water introduced into the system.
I cannot figure it out, and neither can BG. They replaced the ball valve and cock to rule that out and its still doing it.
>What make of store is it for starters and can you post a pic.
I am not sure what the make is, see these pics for some clues?
http://img413.imageshack.us/img413/9621/img0098ji3.jpg
http://img110.imageshack.us/img110/4815/img0099sf8.jpg
(ps: ignore the water marks around the Thermostatic Valve, this was leaking when I bought the house but I replaced the fibre washers and its been fine since, although thats on the mains pressure circuit anyway)
>Reading the posts again (hence the mod) pumping over could be an >option although not one I fancy. If the DHW is causing the valve to run, >then you must have a connection between the tank and the dhw.
BG thought this originally, but since the dripping is NOT when any pump is running they don't think its the case.
>I still think the coil has gone, is there a non return valve on the cold >mains to/from the tank.
When I said about the coil in tank and or boiler gone they seemed to suggest if that was the case "I would know about it. If in the tank, I would get mains pressure water leaking into the tank and that would cause the overflow to go."
Then when I said why not the boiler "I would see leaking at the boiler itself".
I am not sure thats right or not, the guy does seem knowlegable on these systems. I kinda see his point about the tank, and with respect to the boiler I am still not sure, whats thrown me is the fact it drips when the tank temp drops a fair amount (normal boiler cycling doesn't seem to trigger it) through use of hot water or central heating. It seems to be only when the drop is quite a lot after I have ran the heating for a while or ran hot water for a while.
I dont think there is a non-return valve, although not sure what it would look like. There doesnt seem to be anything like that in my pic.
>Is the hot water supplied at mains pressure and heated by passing >through the thermal store?
Yes
>Apart from the F&E tank on the top of the thermal store, do you have >any other "tanks"?
Nope
>Is your boiler a pressurized system boiler with a gauge on the front?
Its not a sealed system.
They also checked for leaks, he came one morning at 8am turned off the ballvalve to the F/E tank, then came the same day at about 5pm after a normal days running and no water was added to the system.
They thought a leak, but I cant see how a leak can be ONLY when the temperature in the tank drops.
They were not convinced to changed the ballcock/valve. Still the same.. I am going mental with this now.
Going to ring BG tomorrow again as when they fitted the new ballvalve 2 weeks ago it was fine, but I think thats because he topped up the water level in the F/E tank.
Cheers,
Mike