Overflowing Central Heating F+E Tank
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Overflowing Central Heating F+E Tank

by andrew-webber » Mon Dec 15, 2008 4:48 pm

I wonder if somebody could please enlighten me as to how my central heating system actually works and so also be able to point me in the right direction with regards to a solving a problem that I am having with it.

I think that I have an open vented , pumped system, if that is the correct terminology!! There are 2 tanks in the loft, one small feed and expansion tank for the central hearing and another large tank to hold the cold water for the hot water cylinder feed.
The boiler is an old Glowworm space saver 30!! There is a single motorised valve (only 2 way) in the pipework and I think that this means that I can either have the radiators on or the hot water on, or both, but if I have the central heating on the water in the hot water cylinder is also heated. Finally there is the pump.

The problem that I am having is that every few days the feed and expansion tank for the boiler / radiators will start to overflow. Checking the contents of the small feed and expansion tank confirms that the water level is just over the overflow pipe level.

I have checked the ball vale and this seems to be operating correctly and shuts off ok. I have taken the surplus water out of the feed and expansion tank on a couple of occasions and all seems ok for a few days, until it fills up again of course!!

I thus assume that the water must be coming back into the F+E tank from the boiler / radiator pipe work? Is this the only possibility? (I have read elsewhere about coils in HWC cracking, but I think that this would cause the cold water tank to fill up, not the F+E tank for the central heating?).I have ran the system for a couple of hours or so and checked the expansion pipe going into the F+E tank in the loft but nothing seems to be coming out of it and the level in the F+E tank seems to be staying the same. It seems to just creep up over a few days, so maybe I need to keep a closer eye on the level on a more regular basis.

Any pointers would be much appreciated, as this is driving me crazy!!

Many Thanks


Steve the gas
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by Steve the gas » Tue Dec 16, 2008 5:45 am

Hi Andrew,

Please adjust the ball valve, adjust the screw with locknut, screwing inwards reduces level. Rough plumbers would bend the arm if metal, downwards into the water.


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