Central Heating F&E TANK OVER FLOWING

[malooga]

Hi everyone,
Wondering if anyone out there knows the answer to my problem.
The small F&E tank for the central heating is filling up with hot water ( Guess system is venting back into f&e tank, and the overflow is freezing up outside when the water cools down causing the tank to overflow into the attic.
PLEASE has enyone got a suggestion on how i can sort out this over venting.
Many Thanks

 

[45yearsagasman]

Thisis caused by a blockage near the cold feed and vent connections in your system pipework.Only way is to cut out and clean or replace affected pipework.

 

[spraggo]

The small F&E tank for the central heating is filling up with hot water (

This could be caused by water passing into the inner coil of the indirect cylinder, which would mean a new cylinder. Can you see water dropping from the ball valve in the larger tank after no hot water tap has been turned on for an hour or so?.

 

[45yearsagasman]

If it only happens when your system is running then its as I suggested.Thats the most common reason for your symptoms.

 

[malooga]

Thanks 45yearsagasman, having read a couple of previous posts as well you are confirming what seems to be the cause.
Yep it does only happen when i run the central heating. It does'nt do it when only the hot water is running.
I thought that it was venting out of the vent pipe into the F&E but the hot water was pushing back up the cold water pipe from the F&E.
The only thing that puzzles me is that in the maze of pipe work in my airing cupboard i found a gate vabe that was shut ( sort of spurring off before the 2 port valve) I opened it up fully and got a lot of gurgling noise, the rads cooled down (did'nt go cold) but the cold water pipe from the small F&E went back to running cold and has'nt expanded any water into the tank.
Now i've just closed the gate valve bach down to nearly shut, the rads have heated back up but at the moment the cold feed is still cold from the F&E?
Will keep an eye on it.
Thanks for your help.
If my last explanation has given you any other indications that it could possibly be something else then i would welcome your comments.

Once again cheers.

 

[malooga]

Thanks spragggo, your suggestion is right up there with 45yearsagasman. There seems to be a few causes to this prob and both of you are confirming that it is definatley a blockage or leak in the coil in the cylinder.
There's no drip from the cold feed in the header tank though if i have'nt used the hot water for a while.

Thanks.