NO I AM NOT AN UNDERFLOOR HEATING EXPERT!

[Harvest Fields]

I am no underfloor heating expert. But would be grateful for any help. Can someone tell me why when the UFH is on and nothing else is on. The radiators get hot. And no it's not the 2 port valves. They are both cold both sides? But somehow the return pipe for the heating gets hot? I'm thinking reversed circulation but cannot see where?

 

[SimonG]

Sounds like reverse circulation. Can only be that if the 2 ports are cold.

 

[Harvest Fields]

Any ideas where I should be looking?

 

[SimonG]

Between the underfloor return and rad return.

 

[Old Account]

Good question though, never came across this type of issue. But if You both think it's the reverse circulation then how does that work

 

[Harvest Fields]

No idea mate. That's why I'm on here

 

[Harvest Fields]

Between the underfloor return and rad return.

I can see where all 3 returns meet as all the valves and the unvented are in the loft with the boiler. How do o fix it mate?

 

[SimonG]

Easiest is to put a non return valve on the heating circuit return just before it tees back on.

My responses are a little slow and out of sink as my posts have to be ok'd.

 

[deg]

Non return valve between the two should do the job if the returns are exposed.

 

[Harvest Fields]

Easiest is to put a non return valve on the heating circuit return just before it tees back on.

My responses are a little slow and out of sink as my posts have to be ok'd.

No worries mate. Been a naughty boy?

 

[Harvest Fields]

I'll give it a go and see what happens.

 

[Harvest Fields]

So I have been back and fitted the non return valves. The rads are still coming on when the UFH is on? Any more ideas?

 

[townfanjon]

Blimey weird one this , is there a pump on the heating and one on the UFH or has sombody tried to use just one ? Bypass anywhere ?

 

[Stigster]

Good question though, never came across this type of issue. But if You both think it's the reverse circulation then how does that work

Here is an example of a system in backflow condition. It's not the same as OP's problem exactly but it does show how it happens in this diagram.

http://www.hertsboilers.co.uk/tech/backflow.jpg

 

[Harvest Fields]

Here is an example of a system in backflow condition. It's not the same as OP's problem exactly but it does show how it happens in this diagram.

http://www.hertsboilers.co.uk/tech/backflow.jpg

Cheers mate. I get the concept. Just don't get why it's doing it now. When it has not for the last 6 years. The owner has not had any work done either.

 

[ShaunCorbs]

Is it all the rads or just some ?

 

[Harvest Fields]

Just some mate.

 

[ShaunCorbs]

Just some mate.

When the underfloor comes on does the flow or return get hot first

 

[Chalked]

I would bet the underfloor return is teed into the heating return. Then teed into the main return.
I should have a dedicated flow and return from the mains.
And so should all other zones too

 

[Harvest Fields]

When the underfloor comes on does the flow or return get hot first

Need to go back and check as it was late and left the owner to test. But have fitted non return on all returns as the are all exposed in the loft. So doubt it is the returns getting hot.

 

[ShaunCorbs]

Need to go back and check as it was late and left the owner to test. But have fitted non return on all returns as the are all exposed in the loft. So doubt it is the returns getting hot.

Unless the rads are on the manifold it's got to be coming through the return

 

[Harvest Fields]

That's is exactly what I am thinking. But I cannot see where. I will go back and check however all three returns are all on the pipework back to the boiler in the loft next to the cylinder

 

[Stigster]

Cheers mate. I get the concept. Just don't get why it's doing it now. When it has not for the last 6 years. The owner has not had any work done either.

That was for Matchless because he asked how reverse circulation works so I just put up a quick post to the diagram. I hope you find what's going on with your problem, it's a bit baffling for sure.

 

[Harvest Fields]

That was for Matchless because he asked how reverse circulation works so I just put up a quick post to the diagram. I hope you find what's going on with your problem, it's a bit baffling for sure.

No worries my post sounded harsh but was not meant in that was either

 

[GH77]

Do you have access to Thermal imaging? ... I've got a FLIR that plugs into the bottom of my phone, use it on UFH all the time, will show you where and how the heat is moving around, if you let the system all go cold then return the next day hopefully that will shed some light on the problem