Reverse circulation?

[elczkc]

Just had extension built with 1 new rad and 1 plumbed in towel rail. Since this was connected I have had problems with radiators getting hot with only the HW on.

Have checked the motorised TWV and this appears to be OK. I have tested for reverse circulation in an existing upstairs radiator and it was clearly present. However the plumber is adamant that this could not be caused by their work.

At his request I checked to see if the newly added radiators got warm with HW only on - they did, but only after some time. Downstairs radiators got hot first. Also the flow in the new radiators does not seem to be reversed, i.e. when I put the CH on the same pipe on the new rad that was getting warm slowly now gets hot fast. My assumption is that this means the reverse flow is going all the way through the other radiators and back to the TWV from where it then goes through the feed to the new radiator and back to the return pipe. From what I've read it sounds like this might occur if they teed into the return pipe after the return from the rest of the system, would this make sense?

Are there any other possibilities that anyone can suggest?

Any help much appreciated - he is pretty confident that it's not his problem and it must have been there all along, but I've lived in the house for 12years and I think I'd have noticed by now! Just want to get my facts straight before I get into a technical discussion!

Cheers,
Martin

 

[ShaunCorbs]

Easy way to tell turn this two rads off and see if the problem goes away / doesn’t happen no more

 

[Deleted member 120897]

Is the TWV a 2 port? Put hot water on and feel the open side of the 2 port valve (if that’s what it is), if it’s hot/warm then I’d say you have let by of that valve.

 

[elczkc]

Thanks for the suggestion - can't believe I didn't think of this.

So, with new rads off problem magically goes away. Think plumber has some work to do...

We're also getting water coming out of the overflow pipe (a stream not just drips) when HW is on, this is coming from the expansion tank not the CW tank. Float valve is closed and underwater! Could this be linked.

Thanks again

Easy way to tell turn this two rads off and see if the problem goes away / doesn’t happen no more

 

[ShaunCorbs]

If you can try removing water from the tank so the ball is not under water nest way keep removing water until the ball valve starts to dribble in and then leave it and monitor could be the level was set too high or the valve has failed best to drain the tank when the system is cold eg no heating on etc

 

[John.g]

Thanks for the suggestion - can't believe I didn't think of this.

So, with new rads off problem magically goes away. Think plumber has some work to do...

We're also getting water coming out of the overflow pipe (a stream not just drips) when HW is on, this is coming from the expansion tank not the CW tank. Float valve is closed and underwater! Could this be linked.

Thanks again

Was there a new circ pump installed or was the setting changed in a existing pump?
Can you show the vent and cold water feed to/from the Feed &expansion tank and where it connects into the system.

 

[elczkc]

Thanks for the suggestion - can't believe I didn't think of this.

So, with new rads off problem magically goes away. Think plumber has some work to do...

We're also getting water coming out of the overflow pipe (a stream not just drips) when HW is on, this is coming from the expansion tank not the CW tank. Float valve is closed and underwater! Could this be linked.

Thanks again

Just quick update. Plumber denied any responsibility at all. Says if there is any back circulation it must have been present already before they did anything.

He showed me where the new rads teed into the return. The pipe they go into appears to be the main return to the boiler - it goes straight up into the loft and back to the boiler with no other tees that I can see. This tee is physically above the HW cylinder so it must be after the HW return tees in.

I asked where the existing rads teed into the return and he said he didn't know and it didn't matter.

I think this is barn door for reverse circulation, anyone have any other ideas?

Thanks, Martin

 

[John.g]

Definitely shouldnr T in above the cylimder, normally the flow/return manifolds would be side X side alongside the HW cylinder (if upstairs). years ago got my attic converted and they Teed in above the cylinder with the flow piipes from the vent pipe and I was getting all sorts of weird circulation until I modified it myself.

 

[ShaunCorbs]

There’s your issue should be before the hot water cylinder return tee eg so cylinder tee is the last tee into the boiler

100% he’s done wrong if it’s the last tee before the boiler