Underfloor heating problem

[Dannypipe]

Hi all, posting this here as I don't want joe blogs putting in his sixpence.

Under floor heating. I'm having a mare with an existing circuit that I've intergrated to the new heating system we just installed.

Apperently (though this can't be proved) it worked before.

Before it was directly plumbed into the old one pipe system, and the only control was a TRV cut into it as it branched off a rad run.

On our new system we have given it a dedicated pumped manifold, thermostat, zone valve, and programmer. The rest of the system (all new) works a treat. The rest of the system (quite big system 37 rads) is zoned and has a main manifold in the boiler room with a pump on each zone. Followed by a one large circulating pump.

The underfloor heating F & R feel warm. The Flow feels a good bit warmer than the return. I powerflushed the underfloor heating before we connected it, and boy was it black.

My hunch, is that the floor which is tiled, might have a very thick screed in which the pipes are buried and there may be no insulation below it. So I'm fighting a losing battle to get it warm. (It was off the whole winter apparently).

That said, on any new UFH we install the floor warms up pretty quickly. I had this on for 3 hours today and the floor temp' didn't change much if at all. Hard to tell as it's a conservatory and the sun warms the floor in places.

I'm up for any ideas, as I'm fresh out, and this is all that stands between me and a much needed final payment!!

Ta,

Danny

 

[tamz]

Could you shut everything else down so the cons floor is on its own? You know it is clear as you powerflushed it. If it was piped in direct before (no mixer) the water temp would have been a lot higher so you may be right about the about the cover and insulation. You may end up having to crank it up a bit. Not ideal but you may have little choice.

 

[Gray0689]

Danny if it's a very thick screed with no insulation underneath the pipes it will take forever to heat it mate you will need to put it on constant for a day to see if the floor warms up and see if the flow and return stabilise to same temp
Could you take a pic of the set up to let us see
Cheers

 

[Dannypipe]

Cheers Gray.

Really days?! OK.

In that case 3 hours really wasn't going to acheive anything. I've never come across this problem before but from the way the system was controlled previously with a TRV valve, is a good indication that the initial install might not have been gold star quality.

I'm not at the job until wednesday, so I'll switch her on and leave it to see if it gets there eventually. Bit of a pain as I just don't know whats occuring under those tiles.

I've been crawling around on all fours stroking the floor, I must look like a right nut job to the other trades.

I'll take some snaps and put them up. Not much to see though as the boiler-room is in the basement, and all you can see is the 15mm Poly Plumb pipe come out the wall and into the manifold. All I have done is extend the pipes to the basment. I pressure tested the pipework, and then a chippie laid an oak floor over the room I ran the extension through. Extension I added to the pipe was about 2 meters, so not much.

Its got me and the old man scratching our heads, but then we always put celotex down on the slab before the screed is laid, and we know the screed will be 50 - 60mm. I have no idea what I'm dealing with here.

The client is going to want to feel that floor warmed before he parts with his money. I'll report back.

Thanks again.

 

[Dannypipe]

Tamz - I have tried running it with the blending valve switched right up very hot. Just desperate to feel some heat on that floor, and also I had it running on its own for at least an hour. I meant to leave it longer individually but forgot to check the programmer and it brought all the other zones on while I was out. So I got back and the house was tropical.

Its a bit of a funny one, but if it can take all day or longer as Gray said, then it might just be a case of leaving it on day and night.

 

[Gray0689]

Is it an oak floor over underfloor?
Solid wood or engineered?
What size of an area is it?
How many circuits in area?
Does it have it's own pump?
Is the return teed in with the mixing valve and manifold return

 

[tamz]

What can make it worse is people are seldom truthfull about how things actually were before you started.
Goiod luck with it Dan. Hope you get something sorted one way or another.

 

[Gray0689]

Sorry dan missed the pumped manifold

 

[Dannypipe]

Is it an oak floor over underfloor?
Solid wood or engineered?
What size of an area is it?
How many circuits in area?
Does it have it's own pump?
Is the return teed in with the mixing valve and manifold return

The Oak floor is just over the last 2 meters as it runs to the basement via the kitchen. The underfloor heating is in the conservatory leading off the kitchen.

Size, I would say 3 X 5M. It is one single circuit. It does have its own pump a cheap and cheerful Wilo on the manifold. It is also getting a kick up the backside from the main circulating pump on the heating return manifold.

The reurn is teed into the return manifold which is 42mm dropping to 35mm into the boiler.

The manifold is a cheap and cheerful Screwfix job. When I switch the isolation valves off halfway on the manifold you can hear the water gushing past.

Its very hard I know to advise on a tricky problem like this via the internet. Very grateful for the replies. I'm suprised to hear it can take so long for the floor to heat up when there is no insulation. So that has been very enlightening and good ammunition when I have to discuss it with the client, and hopefully get paid. Need it, I'm totally skint.

 

[Dannypipe]

Just realised not all of that makes sense! Shame I can't edit it. Bedtime methinks. Thanks for the advise. Will report back on wednesday.

 

[Gray0689]

Ideally there should be 4 inch of insulation on a ground floor house to stop the heat from heating potential a cold sub floor instead of just heating screed it can take roughly about 4 hours to bring a 4inch sand cement screed up to temp and that depends on how well the room insulation is in Walls how much glass it's all about keeping the heat loss down and of course the correct amount of pipe is in to cover the required heat levels
As you can't see what's under the floor it's a bit of a nightmare I'm afraid mate
When you go back set max mixing valve temp normally range from 25c to 50c set on max and as tamz says make sure nothing else on just underfloor circuit

Hope you get it sorted mate

 

[unguided1]

The other thing is the fact that you do not know what the pipe centres were set at, for example if the origenal installer installed them at 300 centres then you will struggle, what may help is to get a lazer thermometer to check the floor out.

 

[Dannypipe]

I've been using an infrared thermometer. Its very weird. There are little warm spots in the floor. Like I said though, the room is a conservatory, so it could just be warmed by sunlight.

Tomorrow I'm going there first thing in the morning and putting the underfloor heating on. Then going off to another job and I'll check on it at the end of the day.

 

[Dannypipe]

Quick update: The underfloor heating went on at 8.30am and I went and checked it at 6.30pm. The floor was nice and warm. So it looks like the slab did just need a Loooooong time to heat. Having only ever worked with my own installs (done properly with insulation) I had no idea it could take so long.

Cheers for the advise. Logged in the head for next time.

 

[Gray0689]

Glad it's sorted for you mate

 

[PlumbBobBob]

good it's sorted i had visions of it going the same way as that joker a few weeks ago lol