UFH not warm enough

[David78]

Hi all,

 

I'm going to apologise in advance as I have limited technical knowledge on underfloor heating and general construction. 

 

I was hoping to get some advice on our wet underfloor heating installed 3 years ago. Its one system across multiple zones. It works really well in the new extension where we have concrete flooring with a microscreed finish. However in the old part of the house we have a room with a joist flooring and engineered wooden flooring and here the heating is never warming up the room. 

 

The floor boards are always cold and a thermometer in the never shows the temperature going up. I checked the in and out pipes on the manifold and all appear warm. I decided to rent a thermal image camera to see if I could spot any problems. All the pipes are appear to be working but the temperature readings are very small 21C compared to the new extension where we get 25C.. See attached photos 

 

I am wondering if this is a normal or expected output? We as a family freeze in the winter and never tend to stay in the room long because of the cold. 

 

I don't recall how the builder installed the pipes but I do remember some insulation went in first then the pipes and followes by the flooring. I assume this is OK? 

 

I'm wondering maybe the heat is getting lost by the fact we have an external solid wall so insulation in the room is clearly not as good as the new extension but I it does not explain why the floor is stone cold.

 

Any advice? 

 

Ps I did spot the builder placed the pump in the wrong direction so the out flow is going through the in pipes and therefore the flows which are set to max do not register any flow. I'm having this fixed by a heating plumber so that might give us more control. 

 

 

[SteamyTea]

Welcome

 

Without more details, it is hard to tell when is happening.

Is the floor you refer to as joisted, got an air void under it, it is it full of insulation?

What sort of floor covering do you have in the area that works?

What are the general heat losses like for the two different areas?

[ProDave]

I suspect the issue is the floor make up between the new and the old.  The new floor will have been built with proper amounts of insulation.

 

The old floor will probably have less.  Did you see what they did to the old room by way of adding insulation under the floor before laying the pipes?

 

The sollution is likely to be to raise the water temperature by adjusting the blending valve on the manifold, and then slowing down the flow rate to the new rooms so they don't heat up too fast wile leaving the flow rate to the old room as high as possible.

[scottishjohn]

I think your piccie shows exactly what is going on .

new section the pipes are showing very bright and concentrated --other piccie shows the heat dispersed all all round the pipes, so the actual pipes not showing as hot --so its likely you have avoid around pipes so heat is going out the bottom and anywhere it wants to and not being directed upwards only to the floor . 

can you get under the old floor to add insulation to stop heat going down  and block any holes at end of floor joists where it can leak out?

Edited May 21, 2021 by scottishjohn

[David78]

4 hours ago, SteamyTea said:

Welcome

 

Without more details, it is hard to tell when is happening.

Is the floor you refer to as joisted, got an air void under it, it is it full of insulation?

What sort of floor covering do you have in the area that works?

What are the general heat losses like for the two different areas?

The builder to put some insulation between the joists where previously it had an air void. He then pinned the pipes to the insulation and then covered it with engineered wood flooring 15mm thick 

[David78]

3 hours ago, scottishjohn said:

I think your piccie shows exactly what is going on .

new section the pipes are showing very bright and concentrated --other piccie shows the heat dispersed all all round the pipes, so the actual pipes not showing as hot --so its likely you have avoid around pipes so heat is going out the bottom and anywhere it wants to and not being directed upwards only to the floor . 

can you get under the old floor to add insulation to stop heat going down  and block any holes at end of floor joists where it can leak out?

I suspect you are right, I feel a big draft from the tiny gaps between the floor boards a d the skirting board, so there must me some hole. Thanks for the advice, will look into it 

[David78]

4 hours ago, scottishjohn said:

I think your piccie shows exactly what is going on .

new section the pipes are showing very bright and concentrated --other piccie shows the heat dispersed all all round the pipes, so the actual pipes not showing as hot --so its likely you have avoid around pipes so heat is going out the bottom and anywhere it wants to and not being directed upwards only to the floor . 

can you get under the old floor to add insulation to stop heat going down  and block any holes at end of floor joists where it can leak out?

I suspect you are right, I feel a big draft from the tiny gaps between the floor boards a d the skirting board, so there must me some hole. Thanks for the advice, will look into it 

[David78]

I noticed that on the opposite side of wall I have ventilation bricks which is possibly what's creating the draft in the room with underfloor heating. I assume these should not be closed off as the joist need ventilation? 

[SteamyTea]

1 hour ago, David78 said:

The builder to put some insulation between the joists

How much, 50mm, 200mm?

Basic 'Celotex' type insulation has a thermal conductivity of 0.03W/mK

So 50mm will give you a U-Value of 0.6 W/m².K, 200mm 0.15W/m².K

 

1 hour ago, David78 said:

covered it with engineered wood flooring 15mm thick 

Oak (as an example) has a thermal conductivity of 0.17 W/mK, so a U-Value of ~11W/m².K

 

[SteamyTea]

As other have mentioned, if it is draughty, then that is a problem.

[scottishjohn]

you could use a space blanket under and across the joists+tape joints-something to stop heat and drafts getting from under house to inside your house through the floor --if you can get to underside of joists--underside of joist needs sealing somehow  as the insulation is obviously not a good tight fit to joists --maybe even spray foam --all depends if you can get to underside of floor

then  can you push celotex+UFH piping up hard to your wood floor and pin it there and seal all edges with tape or something ?

Edited May 21, 2021 by scottishjohn

[Carrerahill]

4 hours ago, David78 said:

The builder to put some insulation between the joists where previously it had an air void. He then pinned the pipes to the insulation and then covered it with engineered wood flooring 15mm thick 

So there is just a gap with pipes in it, then wooden floor? 

 

We have CH pipes running along under our FF hall floor, when the heating is on the floor is warm, when the heating is off the floor is cool - if I was to encase those pipes in something like concrete or biscuit mix and bring that mass up to temp, that same floor would feel warm much longer. I think your floor makeup is not ideal for UFH - we have suspended timber floors - I was going to put in UFH but to do it right and make it work well it was going to need much work - the only way I'd have gone for it was with biscuit mix surrounding the pipes, then I needed to consider loadings on the joists and all sorts. I didn't bother. 

 

If you keep the CH on full time and crank the temp right up does your room ever get warm enough? What are the flow and return temps on the pipes and the flow rate?

 

 

Edited May 21, 2021 by Carrerahill

[Carrerahill]

2 hours ago, David78 said:

I noticed that on the opposite side of wall I have ventilation bricks which is possibly what's creating the draft in the room with underfloor heating. I assume these should not be closed off as the joist need ventilation? 

Correct, buildings must breath or you will be signing large cheques to cover rot issues and damp and all sorts.

 

 

[Temp]

We found our rooms with engineered oak needed higher flow temperatures than tiled rooms. 

 

Whats the heat source? ASHP? Gas? Oil?

Edited May 21, 2021 by Temp

[Temp]

18 hours ago, David78 said:

Ps I did spot the builder placed the pump in the wrong direction so the out flow is going through the in pipes and therefore the flows which are set to max do not register any flow. I'm having this fixed by a heating plumber so that might give us more control. 

 

Is that the manifold loop pump? 

 

[David78]

11 minutes ago, Temp said:

We found our rooms with engineered oak needed higher flow temperatures than tiled rooms. 

 

Whats the heat source? ASHP? Gas? Oil?

Gas

[David78]

56 minutes ago, Temp said:

 

Is that the manifold loop pump? 

 

I'm not technical but I believe so, its attached to the manifold, see photo

[Temp]

Is that temperature gauge reading 50? 

 

Can you take a pic of the whole manifold.

Edited May 21, 2021 by Temp

[recoveringbuilder]

I agree with @Carrerahill, our last house had joists, the ufh pipes had a biscuit mix over them before flooring 

[David78]

15 hours ago, Temp said:

Is that temperature gauge reading 50? 

 

Can you take a pic of the whole manifold.

I hope that helps, I was told by someone that the pump is the wrong way round which makes sense as the out pipes are warmer than then in pipes. Will be looking to change this

[PeterW]

Pump looks upside down - UPS2 has an arrow cast in the body of the pump (not the motor) and I bet that is pointing upward. In this case it should be downward. 
 

10 minute job to switch it over if you can isolate the two pipes into the bottom right of the mixer. 
 

TBH I am surprised it has worked so far as it is pushing against the flow valves and is pulling the wrong way through the mixer. 
 

Out of interest which of the two bottom pipes gets hot first ..? Which is the boiler supply ..??

[JFDIY]

Mixer looks to be in wrong way round or manifolds mixed up.

 

Check supply and return from boiler are correct first, If so easiest fix is to swap upper and lower manifolds over, check pump casting for flow direction arrow as mentioned by Peter.

 

You might need to turn the image below upside down to match yours, but you'll see what I mean.

 

https://www.colglo.co.uk/file.php?filename=UFCHF5530%2F970035.pdf

 

 

Edited May 22, 2021 by JFDIY

[PeterW]

@JFDIY thanks for finding that ..! I agree - manifolds wrong way up ..!

 

@David78 you need to get the plumber to switch the manifolds over - Polypipe System isn’t too complicated and it’s a case of swapping the flow and return manifolds and their controls or putting the pump etc on the other end which tbh is probably a bigger job assuming the boiler flow is into the bottom pipe of the mixer. 

[David78]

On 22/05/2021 at 11:12, PeterW said:

Pump looks upside down - UPS2 has an arrow cast in the body of the pump (not the motor) and I bet that is pointing upward. In this case it should be downward. 
 

10 minute job to switch it over if you can isolate the two pipes into the bottom right of the mixer. 
 

TBH I am surprised it has worked so far as it is pushing against the flow valves and is pulling the wrong way through the mixer. 
 

Out of interest which of the two bottom pipes gets hot first ..? Which is the boiler supply ..??

The bottom pipe is the one which gets hot first. Is that correctly setup? 

[PeterW]

Yes - bottom right should be boiler feed. One up is boiler return. 
 

I am wondering how they got this so wrong ..!!!

 

@David78 is there anything on the left end of the manifold..? Or is it just caps..?