Expansion tank overflow now that new condensing boiler has been fitted.

[WickedestSound]

Hello.

I've just been reading through this great site and thought I'd post my issue here to see if anyone can help please?

We have an open vented, fully pumped (I could be wrong) central heating / hot water system and just before Christmas our 20+ year old bolier started leaking at the heat exchanger. We called in a friend who has a plumbing business and had the boiler replaced with a GlowWorm condensing boiler. I don't think the old boiler was a condensing one. He also flushed the system with flux and sludge remover, fitted a gold magnetic filter to the return pipe near the boiler and all was well.

After a couple of days we started noticing water outside on the patio. It turns out this has been coming from the feed and expansion tank overflow pipe.

What is now happening is that once the pump shuts off, roughly half a pint of water is coming out of the vent pipe which goes up and then down over the expansion tank. It only happens after the system has run and the pump shuts off. After a while the level in the expansion tank rises enough that it just reaches the overflow and hence the water outside.

The system worked fine before the boiler switch over. Things that have been tried are opening a bypass valve (I'm sorry but not sure what this is) and also turning down the pump from 3 to 2 but the problem still exists.

We are in a bungalow that has had 3 rooms built into what was the loft space. The layout of the system is the boiler on the ground floor with the hot water storage tank above it in the same cupboard, and then upstairs in what's left of the loft we have the cold water storage tank and the feed and expansion tank. 3 radiators upstairs and 7 downstairs.

The heating and hot water works fine, all radiators get fully hot but there's this water from the vent after the pump shuts off. The water is clear and cold.

Sorry to go on a bit but we can't seem to pinpoint what might be causing it.

I know it's hard to comment without actually seeing it but if anyone can offer any advice on this please then I'd be really grateful.

Thanks for reading.

Alex

 

[doitmyself]

Could be the feed pipe from the F&E tank to the boiler flow pipe is blocked.

Lock your motorized valves in the MAN position then drain some water out of the system (drain cock usually on the last radiator) while someone watches the water level in the F&E tank. If the level does not drop and the ball valve open, the pipe is definitely blocked.

If no blockage, let the water cool down and then check how deep the water is in the F&E tank. It should only be about 2 inches above the bottom outlet. You can change this by bending the ball valve arm. Check by draining some water and noting where the ball valve opens. Make sure it is before the water level reaches the outlet.

 

[WickedestSound]

Thanks doitmyself.

I don't think it's a blocked cold feed as he can drain down the system and then fill it up again. We have the heating on at the moment but if memory serves when the system is cold the F&E tank is only 1/3 full and roughly 2 inches above the cold feed outlet.

Any other suggestions please?

Many thanks

Alex

 

[Paulus]

I racked my brains over exactly the same problem. One of the guys on here (sorry I can't remember who) finally suggested a new float valve in the f&e tank and was spot on. I cleaned out the tank, fitted a new valve and reduced the amount of water in the tank slightly and have had no problem since.

It may be worth a try. .

 

[doitmyself]

The water level rises when heated up.

Is it a combi boiler (no HW cylinder)? If yes, turn the pump down from 3 to 2.

 

[jtsplumbing]

Can you let us know what model glow-worm boiler has been fitted ? then we may have a better idea what is going on ! eg; hxi / sxi / Flexicom / Betacom but more information on boiler type will be helpfull.
:sleep1:

If it is a combi you should not have a expansion tank (fix`d speed pump you can-not slow it down) :8:

 

[WickedestSound]

OK sorry for the delay getting back. Thanks for all the replies.

It's a Glow-Worm Flexicom 18hx which I think is a condensing boiler. I don't think the old one was a condensing one.

The pump was set to 3 so as suggested I changed it to 2 and while it made the system quieter the water still comes from the vent pipe.

Today I have tied off the float valve and reduced the water level in the expansion tank so that the water level is just 2 inches over the top of the feed pipe. It was about 5 inches before I reduced it.

I ran the system tonight on it's hour program but alas once again once the pump shut off the water came out of the vent pipe.

My plumber's not getting back to me about it either which isn't helping.

Does anyone have any other suggestions please?

Thanks again.

 

[dancinplumba]

did water level still rise ?

 

[WickedestSound]

I actually can't say hand on heart that it did. It looked as though it was higher but I didn't measure the level as I did when I took some out this afternoon. I think it was a bit higher though.

Sorry I can't say for sure...

 

[dancinplumba]

leave ball valve tied up for a while, make 100% sure its not passing/dripping and see if it rises, if it does, could be leak on dhw heating coil, if it doesnt, could be you have too much resistance on heating circuit, does it do it on dhw heating only as well ?