UFH Design for extension, UVC? TS?

[jack]

We have an ASHP with flow and return pipes flowing through the EPS underneath it.

 

There are 3 x 100mm layers of EPS under the slab. We cut two channels in the middle layer , deep enough to take polypropylene push fit pipes. Can't remember the size - 60mm? 

 

I went with polypropylene because it was cheap and handles high temps pretty well. The highest temp it will see is 55 deg C from an ASHP, which is well within limits. I bent one end up into the plant room on a long radius.

 

We foamed those place, then covered with the top EPS layer. 

 

We used (from memory) 28mm Hep2O barrier pipe, to which I stuck strips of thin nitrile insulation - 3mm or something like that, I think it was. Then I threaded that through a length of cheap plastic film tubing. A touch of washing detergent on the outside of that and it pulled through pretty easily.

 

Seems to work well for us, for both UFH and DHW. If you're just using it for UFH, the extra stuff I did is probably overkill. In fact, if I were doing it again I'd consider just pulling the Hep2O pipe straight through without all the extra insulation and tubing. 

 

14 minutes ago, Tin Soldier said:

The reason I ask about a conduit is that I would need the ends of the pipes to be exposed by about 8 meters at the edge of the new slab, to allow me to channel out an insulated route through the existing slab, once we break through.

 

Not sure I follow this. Could you explain a bit more what you're doing?

[Tin Soldier]

I'm building a house sized extension adjacent to an existing property.

 

The founds/slab and blockwork are going in January - February, prior to the panel company erected the extension in april

 

I will be opening up the existing property to accept the union with the new extension in March. it requires the wall to be raised, rsj in etc.

Once I'm into the existing property the intention was to channel the UFH Manifold Flow and return and flow pipes into the existing slab all the way to the thermal store- circa 8 meters.

I'd rather not open the house to the elements whilst the groundworks are being done, so I'm looking at ways of laying the pipe/conduit in the insulation,so I can get to it when I'm opening up

 

I don't know if its possible, but I can hope

[Tin Soldier]

jack, any chance you could point me in the direction of this 60mm pipe?

 

from what I can find its normal to run 22mm pipe flow and return to UFH Manifold

 

are you saying that these pipes are run through a 60mm conduit?

[Nickfromwales]

3 hours ago, Tin Soldier said:

From what I can find its normal to run 22mm pipe flow and return to UFH Manifold

 

are you saying that these pipes are run through a 60mm conduit?

22mm is the norm. 

22mm pipe will need a 60mm conduit all to itself if it's to be pulled in / out.

Tbh the Hepworth pipe can sit directly in the insulation, as @jack suggests he may do if ever building again, but I'd advise against that as the clicking / creaking noise of the pipe moving against the EPS may drive you nuts. My mate foamed his pipes into IWI covered walls and the noise of them when the heating is cycling is very apparent .  

[Tin Soldier]

Ok definitely conduit

 

so each 22mm pipe needs its own 60mm conduit?

 

is the conduit like unperforated land drain coil (black ribbed stuff?) struggling to tiny 60mm conduit otherwise

[jack]

I suspect it was 50mm drain pipe, something like this: https://www.drainagecentral.co.uk/50mm-Push-Fit-Waste-Pipe-x-3m-W9800

 

Just to be clear, I'd still use this if I were doing it again. I just wouldn't bother with the strips of insulation and plastic tubing.