Single Room Underfloor Heating

[audis]

Hi All,

I have installed UFH in my kitchen extension. Problem is to get it started. I can feel that hot water is going trough pump, but no heat water is coming back. So I thought either it's connected wrong or I have a air in the system. Please see file attached with pipework explained. So this circuit is connected where old radiator used to be. Rest of the system, I mean radiators is working brilliant. Just wanted to make sure everything is connected correctly. Although I tried to get some air out by unscrewing nut in the middle of the pump, as far as I can see only water coming out, no air. Please please if you know anything let me know. It's getting colder soon, don't want to freeze pipework. Thanks a lot.

 

[gassafe]

Is the pump running... Have you set the blending valve correctly?

How was it commissioned, I like to flush water through the loop to get all the air out!

 

[Ermintrude]

Air lock. Turn off flow and return, fit a drain cock on the return (perm) and run off about 20L .

Also the floor will take up to 4 days to get warm initially

 

[audis]

Even if it need up to 4 days to heat up, I still should feel hot water on my UFH return pipe? I will do like you said. Does it looks like everything is connected corectly?

 

[audis]

Yes, pump is running. I did run water for a while through the loop before closing isolating valves, in theory there shouldn't be any air locks.

 

[Sharp Point]

Yes, pump is running. I did run water for a while through the loop before closing isolating valves, in theory there shouldn't be any air locks.

First of all what size is the room and how long is the pipe length?

 

[Chalked]

Single zone sould not be connected yo radiator circuit.

It should be piped back to the main flow amd return from the boiler. The problems you have are twofold.
One . As above,you need to clear the air.
Two . pipe back to mains. Underfloor needs a constant supply. Every time your time clock, or room thermostat turns off you will loose any heat scorce.

 

[audis]

Room is about 12 Sq.m and pipe lenght was around 60-70 metres.

 

[audis]

Single zone sould not be connected yo radiator circuit.

It should be piped back to the main flow amd return from the boiler. The problems you have are twofold.
One . As above,you need to clear the air.
Two . pipe back to mains. Underfloor needs a constant supply. Every time your time clock, or room thermostat turns off you will loose any heat scorce.

My mate connected the same way as I did and it works fine for him.

 

[audis]

First of all what size is the room and how long is the pipe length?

Room is 12 Sq.m and pipe lenght was around 70 m.

 

[Sharp Point]

Room is 12 Sq.m and pipe lenght was around 70 m.

What pipe centres, the distance from pipe to pipe ? What insulation have you used underneath?

 

[audis]

What pipe centres, the distance from pipe to pipe ? What insulation have you used underneath?

It was around 15cm between pipes, and I used 100mm Kingspan insulation.

 

[Sharp Point]

It was around 15cm between pipes, and I used 100mm Kingspan insulation.

Well, you've ticked the boxes for me. Like what said previously, it needs to come off main circs from boiler and zoned. Also it's okay to just connect onto old rad pipes, but those rad pipes could come from an undersized heating system pipe work.

 

[audis]

Well, you've ticked the boxes for me. Like what said previously, it needs to come off main circs from boiler and zoned. Also it's okay to just connect onto old rad pipes, but those rad pipes could come from an undersized heating system pipe work.

By undersized you mean if pipework for old radiators would be microbore 8mm or 15mm pipes?

 

[Sharp Point]

By undersized you mean if pipework for old radiators would be microbore 8mm or 15mm pipes?

Them pipes you connected to may be already branched off other 15 mm pipe that serves anywhere from 1-6 rads for example, so the water is undiluted with heat....if you get me?

 

[audis]

Them pipes you connected to may be already branched off other 15 mm pipe that serves anywhere from 1-6 rads for example, so the water is undiluted with heat....if you get me?

Got it! Will check, need to lift some floorboards! Question, if my boiler flow to UFH loop comes very hot it wouldn't be the case this time?

 

[Sparkgap]

Single zone sould not be connected yo radiator circuit.

It should be piped back to the main flow amd return from the boiler. The problems you have are twofold.
One . As above,you need to clear the air.
Two . pipe back to mains. Underfloor needs a constant supply. Every time your time clock, or room thermostat turns off you will loose any heat scorce.

If you've already run water through the circuit there shouldn't be any airlocks.
There shouldn't be any problems connecting to a rad circuit provided the main pump and feed pipe sizes are sufficient to get the required amount of hot water to the manifold. Don't forget the mixing valve will drop the water temp to something like 40C and UFH systems are normally sized to give about 5C difference, so the return will be 35C once it's up to temperature.
It looks like 15mm pipe so if you've got 70m of it I'd estimate about 7 mins before the hot water you stuck in at one end comes out the other. Unfortunately, this water will have given up all its heat to the slab so will still seem cold. You'd need to have the heating on for several days before you'll find the return temp rising.
Another thought, if this is the first time its being used you should really bring the heat on gradually by turning the mixing valve down and slowly increase the temp over following days by about 1C per day. Stops the screed cracking, but this is mainly on commercial installs, you might be okay with such a small room.

 

[audis]

Thanks all for replies!! Was really helpful! I think it was just the case where I expected return flow from UFH be quite warm after short term! Now I turn the UFH on for 1 hour and already can feel the floor warming up, will give you more update later on how it works!
Question, if the concrete is about 4 months old, it still should be ok to start heating it up with like 40C as the curing period for concrete was done after first 28 days off it's life, is that ok? Or it could still cause cracks?

 

[PlumbBobBob]

no it still could cause cracks. you need to increase the temperature slowly over several days if not weeks really.

 

[audis]

no it still could cause cracks. you need to increase the temperature slowly over several days if not weeks really.

Thanks, will fallow this guide.