Underfloor heating not receiving hot water

[240514]

Could someone please help me identify the issue with water filled underfloor heating system which seems to be circulating water through all pipes on the manifold but the water being circulated is cold even though pipes that come out from boiler and connected to the UFH system are very hot.

Here are pictures of the system:



(more pictures of the whole boiler setup below - really don't understand why there is also a water tank if it is a sealed system - both pipes going to and from the tank seem to be just connected to the same supply pipe coming out of the boiler - what is the purpose of this?
can anyone understand how this whole thing supposed to work?)










I had expensive local plumbing company looking at it, they flushed all pipes with an external pump to make sure there is no air in the manifold but it didn't help at all.
When the Grundfos pump is running I could see all flow meters showing steady 1-2 L/min flow in all sections, however, it seems to be just pumping cold water around.
Both top and bottom pipes to the right of that valve with red head are very hot but none of the hot water seems to be getting into the manifold connected to the left of the pump on those pictures. The only non-standard configuration here seems to be that the pump is about 5 meters away from where the actual manifold begins i.e. the top picture and the one below are in different rooms.

So, the question is what's wrong here - could it be that the mixing valve is faulty or something is not right with that Honeywell thermo-switch connecting top and bottom pipes from the boiler (I already tried removing it completely with no effect)? or is it something else entirely?

Thank you to anyone who could explain in details how this is supposed to work anyway i.e., how is the hot water supposed to get into the manifold at all and what could prevent it from doing this.

 

[kris]

If the water is coming near the manifold hot id bet instead of entering manifold its circulating through the bypass but youd have to look at why its not entering manifold. Theres no way every actuators not working so my guess is what evers powering the actuators is faulty and none of them are lifting. This would be either zoned stats or somthing else.

 

[kris]

What type of control or room stats have you got installed for controlling your heat output for each room/zone??

 

[SimonG]

You have connected the flow and returns the right way round, from the boiler?

 

[240514]

You have connected the flow and returns the right way round, from the boiler?

I didn't change anything - this system was installed 9 years ago when the building was built, I just bought a flat with it recently and found UFH not working. Although, neighbors have exactly the same system and they claim it is working at their flats.

 

[kris]

Good one simon that would defo cause it. I suppose there are guys out there dumb enuf to do this.

 

[240514]

If the water is coming near the manifold hot id bet instead of entering manifold its circulating through the bypass but youd have to look at why its not entering manifold. Theres no way every actuators not working so my guess is what evers powering the actuators is faulty and none of them are lifting. This would be either zoned stats or somthing else.

well, i would say the hot water is NOT coming near the manifold. It doesn't get passed the pump...

i did remove all actuators to test that it is not them

 

[kris]

Who ever did it isnt very neat as still green flux on fittings yuk.

 

[Ermintrude]

Bypass possibly . As the flow meters showing a flow my money on the bypass of the red blending valve being set wrong or just kaput.

It's been set up wrong. The blending vale is in wrong place in respect to pump. Which nugget set this up?

 

[Ermintrude]

Connect top rhs pipe to the red (hot) side of the blending valve (red top) connect the return from the manifold (bottom left) to the other side of blending valve. The outlet of blending valve goes onto pump inlet and then pump outlet onto top left. Set the white head on to a branch off of the bottom left on to the bottom right. Boom it works like it should.

I can come and do it for £1200 and commission or just do as I say and you will be a happy bunny!

 

[Ermintrude]

Actually first off the top pipe into the white valve needs to be blanked off and the white valve connected to the top left pipe before the blue valve (left hand side of the valve)

So the white pipe will link top left to bottom right. Just to test this theory put a gate valve in place of the white head , set gate valve to 1/2 closed and run system. If this works put white head back in .

Try this first.

 

[240514]

Actually first off the top pipe into the white valve needs to be blanked off and the white valve connected to the top left pipe before the blue valve (left hand side of the valve)

Try this first.

Thanks, can you please explain the reasoning behind this - what will this achieve?

 

[SimonG]

Good one simon that would defo cause it. I suppose there are guys out there dumb enuf to do this.

Yes, me once

 

[Ermintrude]

Thanks, can you please explain the reasoning behind this - what will this achieve?

Look at the pump basically it's a closed loop, the tmv and Honeywell are irrelevant as the flow is going to go through pump. When the tmv opens up for cold it's not got any where for the water to go.

I'm assuming that the Honeywell white valve opens when one of the pipe stats is cold thus creating a route out of the system. ?
Just looks a bit of a hash to me.

Also fit an ISo just before where the Honeywell joins the pipe from tmv, so that all the water from the tmv passes on to the pump.

What are those two limbs of brass above and below pump supposed to do? Differential flow?

 

[240514]

What are those two limbs of brass above and below pump supposed to do? Differential flow?

No idea, they have no markings other than labels: supply (bottom) and return (top).

It seems to me that pump+tmv+those brass limbs are part of one pre-assembled unit like they are selling now for example:
theunderfloorheatingstore.com / manifold-pump--mixing-valve-unit-2669-p.asp

but older version with larger tmv... in which case the tmv is to the right side of the pump, wouldn't you agree?

 

[bmwamac]

Gents, I would suggest that unless it's been modified (and why should it have been) then the piping would be correct. I had a very similar experience about 2 years ago. It turned out to be the mixer valve broken. The spring was damaged and the seal badly worn. In the end it was a trip to poly plumb for a complete new manifold, mixer and pump.

 

[Ermintrude]

Assumed it was a new fix. Bizzar arrangement.

 

[bmwamac]

Assumed it was a new fix. Bizzar arrangement.

You may be correct I just assumed it was existing. I'm sure we'll get to know shortly.

 

[Ermintrude]

No your set up looks similar and appeared to work with just valve change. Might be bypassing through white head. Or tmv set wrong or even backtofront. Just looks poor design and pita !

 

[240514]

Gents, I would suggest that unless it's been modified (and why should it have been) then the piping would be correct. I had a very similar experience about 2 years ago. It turned out to be the mixer valve broken. The spring was damaged and the seal badly worn. In the end it was a trip to poly plumb for a complete new manifold, mixer and pump.

Thank you, may I ask what was the reason for changing everything?
Did you try the valve first but it didn't solve the problem?
Just trying to decide whether to proceed with just valve change or go straight for valve and pump replacement.... my pump seems to be working though.

 

[kris]

http://s7g3.scene7.com/is/image/ae235?$p$&layer=0&size=281,281&layer=1&size=281,281&src=ae235/78267_P
http://www.ukplumbersforums.co.uk/a...t-receiving-hot-water-img_20140524_102408.jpg

see difference

 

[kris]

oops mistake

 

[kris]

Im with ermi on this it looks like its been asssembled wrongly,

 

[kris]

JG Speedfit Pump & Mixing Valve | NoLinkingToThis

 

[240514]

Im with ermi on this it looks like its been asssembled wrongly,

Thanks, so if it was wrongly assembled it means it has never worked - what are the chances that no one noticed it in the last 9 years it's been there?

Unfortunately I cannot contact previous owners to confirm whether it has ever worked but presumably it was approved by NHBC when the building was commissioned...