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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!
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    Do you have any idea of the operating temperature for the UFH? Mine works at just below 40 degrees (and barely perceptible on the floor surface) - but that's under timber floors in a well insulated house - under concrete it could be a fair bit higher especially if the thermal insulation of the building in general isn't great. Even at 40 degrees there's be reasonable de-rating factor (compared with the tabulated ambient of just 20 degrees for a buried cable).


    I'm not sure how much benefit there's be putting the cable below the insulation - it should be a little cooler there of course, but with insulation and a higher temperature layer above and a long way sideways to free air it's hard to see where the heat will go (other than downwards into the ground). It's not that long ago building regs didn't require insulation for floors with a large area compared to their perimeter - since once it had warmed up the heat loss downward into the ground was considered small.


    There's no alternative route, I suppose?


        - Andy.
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  • 0
    Do you have any idea of the operating temperature for the UFH? Mine works at just below 40 degrees (and barely perceptible on the floor surface) - but that's under timber floors in a well insulated house - under concrete it could be a fair bit higher especially if the thermal insulation of the building in general isn't great. Even at 40 degrees there's be reasonable de-rating factor (compared with the tabulated ambient of just 20 degrees for a buried cable).


    I'm not sure how much benefit there's be putting the cable below the insulation - it should be a little cooler there of course, but with insulation and a higher temperature layer above and a long way sideways to free air it's hard to see where the heat will go (other than downwards into the ground). It's not that long ago building regs didn't require insulation for floors with a large area compared to their perimeter - since once it had warmed up the heat loss downward into the ground was considered small.


    There's no alternative route, I suppose?


        - Andy.
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