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

[LeakFinder's]

get a local plumber to complete a pressure test on the domestic hot if it holds pressure fine get the heating set up as a pressurised system as it could be purely pumping over. if it fails get the coil on the cylinder bypassed and see if it still occurs. if it stops then likely a perforated coil and needs the cylinder replaced.

 

[doitmyself]

What is the vertical distance from the pump to the water level in the F/E tank?

2 metres

That's good.

What is the vertical distance from the water level to the top of the bend in the vent pipe?

30cm

That's not enough. It needs to be at least 45cm and preferably nearer 60cm.

 

[jtsplumbing]

Has the installer wired the pump back to the new boiler ?? dont think the old fuelsaver had pump overrun !!

 

[rocketmanbkk]

sounds like one pipe circulation to me?

 

[WickedestSound]

Hello again,

After reading the replies here and a bit more research online I am starting to agree that the top bend of the vent pipe is not high enough and therefore the vent pipe cannot retain the surge water when the pump stops.

The F&E tank in our loft is fairly close to the pitched roof. As the vent pipe cannot be extended vertically much higher than it is already can it be raised if it followed one of the rafters up at say 45 degrees (or thereabouts) until it reached 60cm please? And then bend around in a U shape and come back down over the F&E tank please? At the moment it comes up at 45 degrees and just has a right angle bend in it so it then goes down at 45 degrees and sits over the tank.

Also I am attaching a picture of what I believe is the cold feed and vent pipe above the pump as one of you asked to see this. I believe the cold feed is the smaller diameter pipe and the vent pipe is the larger one.

Hope this helps!

Thanks for reading.

 

[WHPES]

Is there an automatic bypass valve fitted? (If not there should be)

I had this problem once - Put your motorised valve(s) to the manually open position (lever on the side and locking lug) and see if the problem still happens then. If not it could be a wiring / electrical issue.

 

[rocketmanbkk]

from the top of the tank where the pipe comes out, the pipe should extend at least 450mm and then the vent pipe should go to the F & E in the loft, any less is no good as you will (may) get one pipe circulation, take a photo of the top of teh tank and post it here, we need to see it, measure it also and tell us how long it goes alsong until the vent is cut in.

 

[WickedestSound]

Thanks rocketmanbkk. OK, here's the pictures of the F&E tank. The first picture shows the F&E tank with the vent pipe over the side. There is only 30cm from the top of the bend to the waterline in the tank. People have said this is too low.

The second picture shows the back of the F&E tank with the vent pipe going down almost 80cm where it comes alongside the cold feed pipe. The third picture shows both the cold feed and vent pipe running next to each other on a downward slope over to the corner of the house (run must be 2.5 - 3m).

The last picture then shows the cold feed and vent pipes comes down through ceiling and then over to meet the rest of the pipework just before the pump.

I hope this helps.

Thanks again...

 

[rocketmanbkk]

OK, but the water vessel in the airing cupboard, the hot water pipe come out the top (?), it should the immediately at 90 degrees branch of, then, at a minimum distance of 450mm the vent pipe should going to the F & E tank, is the 450mm there? If not, water will go back in the water vessel (maybe) but it will also go up the vent pipe as its an easier route, it must extent 450mm minimum before you can cut the vent pipe in.

What is the measurement?

 

[rocketmanbkk]

sorry about my spelling! note to self, remember to spell check!

 

[WickedestSound]

Rocketmanbbk - Sorry, I'm confused now. You're saying that the hot water tank in the airing cupboard should vent into the central heating F&E tank?

 

[dancinplumba]

OK, but the water vessel in the airing cupboard, the hot water pipe come out the top (?), it should the immediately at 90 degrees branch of, then, at a minimum distance of 450mm the vent pipe should going to the F & E tank, is the 450mm there? If not, water will go back in the water vessel (maybe) but it will also go up the vent pipe as its an easier route, it must extent 450mm minimum before you can cut the vent pipe in.

What is the measurement?

whats this ? this thread has nothing to do with hot water cylinder

 

[rocketmanbkk]

I apologise, got the wrong end of the, note to self, read threads better!

 

[WickedestSound]

Simon F - I see what you mean about the ports now. We have a 1 x 3 position valve.

The pump seems to be wired to the boiler because the boiler turns off and the pump continues to run for about 5 minutes. The issue of water from the vent pipe only happens for a few seconds once the pump stops.

I think it is just a bounce in the water and as the top of the vent pipe is only 30cm above the water line in the F&E tank a little spills over.

What do you think please?

I'm thinking of getting someone in to raise the vent up.

Thanks all.

 

[WickedestSound]

Sorry for the delay in replying. The plumber came back today and raised the vent pipe up so that the top of the vent pipe is now 60cm above the top of the F&E tank and about 70cm above the water line. The pipe then comes back down with the open end about 10mm below the top of the tank (but well clear of the waterline).

No water comes from the vent at all now, either at system switch on, while running or at switch off.

Many thanks to all who helped on here. Raising the vent pipe was the way to go!

We've also left the Grundfos pump on the number two setting as the system works well on it (was on three before).

Alex

 

[Boilerbud]

Is your pump correctly wired? Your boiler might have pump over run build in but if it is incorrectly wired it wont work. Look at installation instructions for pump wiring. Might work to make open vent pipe higher as no pump over run on your boiler.