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  • UFH maximum sqm per loop?
  • Premier Icon 5plusn8
    Free Member

    The excellent plumber has advised that my 20.14m2 extension will need two loops (on one thermostat) to keep the temp even -apparently longer loops – bigger area will lose heat from one side to the other.
    However everything I have read is that 20m2 is the max for one loop- and I am just bang on it.

    Risk it with one loop or crack on to two?

    Premier Icon leffeboy
    Full Member

    i’m not sure how true that is.  When I did ours it runs in a sort of spiral round the outside 0f the room in to the centre and then back out along the same spiral so it is it isn’t a case of one side being colder but rather from outside to inside and even then it should spread a bit as the pipe runs back along the same route.  It might depend on the system you are using for holding the pipes in place and the sort of pipe.  Ours was thick plastic pipe that you pushed onto a ‘lego brick’ type of plastic pad on the floor.  Covers just over 20m2 as well

    I would crack on with one BUT I can’t see that it would cost much more to do the two.

    Premier Icon lesgrandepotato
    Full Member

    If it’s what the plumber wants, it’ll cost a couple of quid more on the manifold if anything. I’d do it his way. If it doesn’t work otherwise it’s not going to be a good conversation.

    Premier Icon 5plusn8
    Free Member

    The manifold is installed already, with a spare loop ready for the new extension when its built. It would mean scrapping it and buying a new manifold.

    Premier Icon Stoner
    Full Member

    the limitation is not square metres as such, but total length of pipe.

    The length of pipe in a zone will be a function of the laying density (i.e. pipe centre to centre measurement in whichever configuration you choose – I favour flow and return spiral)

    The recommended maximum pipe run is 100-110m

    If you do 200mm spacing, you will need c.5m of pipe for each m2, so 20m2 will be 100m and so should be doable with 1 circuit.

    However the spacing is a function of the heating requirements – total KW or BTU of energy for calculated as necessary to heat the space required, which is a calc your plumber should be able to provide based on the u value of the walls, ceilings/roof, and floor of the extension.

    In a well insulated  new extension you might be looking for say, 100W m2 and at 50deg water you might need 100mm pipe spacing to achieve that depending on the system installed (rails, staple or grids) in which case its 2 circuits not 1.

    Premier Icon 5plusn8
    Free Member

    OK, now I understand. Thanks for the detailed explanation.

    Premier Icon Bear
    Free Member

    You’re also need to be careful to not have the surface of the floor too hot which too much pipe might do.

    Stoner – well insulated buildings will be way lower than 100W per m2. Should be half that.

    Premier Icon Stoner
    Full Member

    indeed, It’s about 65w/m2 isnt it?

    I thought that looked a bit high from the ref I was reading.

    Good to see you still around Bear 🙂

    Premier Icon 5plusn8
    Free Member

    The new extension will all be to modern building regs – eg walls are block internal, cavity with insulation, brick external, roof is part glass 28mm thick and part flat roof with 150mm insultation. Its 4.9 by 4.6 internal as measured this morning which is actually more than the plumber measured  22.54m2 .

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