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SWA in U/F floor slab

whjohnson
Got a job where a new submain - approx 25 metre run in 16mm 3 core SWA. Embedded directly into a new concrete floor where wet U/F heating will be installed. Am trying to work out the best order of installation - that is, should the cable go in first, then the insulation, followed by the U/F pipework,and finally followed by the slab. Am not sure what order the u/f heating side will be installed and am also thinking about how if any correction factors may need to be applied for the current carrying capacity. I have sized the cable with a little overhead in mind in terms of actual final demand, but am still a little concerned about final slab operating temperature

Comments welcome.

PS - Am not liking this new format - it is like writing inside a letterbox when compiling posts!
  • Former Community Member
    0 Former Community Member
    davidwalker2:

    My own UFH system is wet.  It comprises concrete slab, insulation, UFH tubing, engineered wood floor.  It is driven directly from a combi boiler, the boiler water i.e. the UFH water, cycles between 35 degrees C and 45 degrees C, the thermal inertia of the floor smooths this out and the floor is pleasantly warm to the foot, probably around 38 - 39 degrees.

     


    That's incredibly hot for UFH - BS EN 1264 Part 2 provide maximum foot comfort temperature of 29°C for living areas and 33°C for wet rooms


    OMS


  • 0
    Indeed. My electric UFH is set to limit the board temperature to 23 degrees and that is as hot as I can stand. (the room temperature stat is set to 21 degrees)

    Most tile adhesives have maximum recommended temperatures of 26-27 degrees.


    regards
  • 0
    Oh!  My 38 degrees was a guess based on it feeling warm to the touch - I have measured it in the bathroom (porcelain tiles and easier to measure) and it is 28 degrees.  Now I think about it, bath and shower water is around 38 degrees.  My mistake and shows the danger of guessing.


    David
  • 0
    Had a chat with UFH people about final slab temp.

    They said -
    1. Max operating temperature of slab?
    Answer - Do you mean the floor/screed? If so the flow temperature of the water will vary between 25 – 45 degrees C which will give an average floor temperature of 5 – 25 degrees C.

    They also said that they run the pipework aroiund 100mm from walls, so I guess I have that to play with for my cable.

    UFH pipework is fixed at 150 centres elswhere so I might ask if they come another 50mm away from my cable run.
  • 0
    sounds like there will be a concrete slab, then insulation, then ufh coils clipped to the insulation then a screed poured. The cable would live very nicely in the concrete slab no problems. The screed will have perimeter insulation fitted, so running it in the screed at the edge will make little difference to heat loss of the cable.

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