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Underfloor heating

Discussion in 'Plumbing and Central Heating' started by deuce22, 28 Aug 2010.

  1. Biggles..

    Biggles..

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    Delta

    No i gave a rule of thumb HVAC calculation that is proven for all commercial appliacations and is deemed to be far to high for domestic standards build to current regulations.

    Basic principles would suggest that if the op actually needs more than 100w/sqm then ufh isnt the best option.secondly id assume that the heatloss calc is massively inaccurate.

    most systems we design run with water temp between 45 -60 acheiveing floor temps no greater than 30 with an average room temp at 21. assume 8deg diff between flow and return.

    in practice that means to acheive the ops original 200w/m you would have a room temp of 20,flow temp of 55,100mm spaces, bare concrete,a floor temp of 38 and still not acheiving 200w/m.

    what ufh companies say is they can acheive 100w/m not to design at this figure.

    100mm spacing is normally only needed for low temp inputs ie ashp etc rather than gas/oil fired.

    personally we'd be using 18/22 ufh products.

    have seen,fitted and designed systems that run 12 ports easily and competently over 100m loops with no adverse effects.thats not to say youve seen some that dont, but.same can be said that ive seen plenty of small systems that dont work.

    as for cross connecting thats each to there own,personally i dont like it,id much rather have even loop sizes for easier balancing.

    based on the ops revised figure of 5000watts

    it would be room temp 20,flow temp55,floor temp30,thick wood coverings,200mm spacings.15mm pipe.250m pipe.
     
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  3. looneyfitter

    looneyfitter

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    I assume you mean directly to the concrete? I have as a precaution used the foil insulation i have mentioned as a second insulator and for piece of mind then clipped to that.

    Then do as described.

    I would seriously go for 100 centres and a max of 100lm per 10m2 tho. I have gone for between 130-150centres but that was just how I did it. If i had, more experiance when i did the job on my own house, i would have designed it a little better (layouts etc) so i could reduce my flow temp more.

    But hey it works perfectly well on the set back timers i have, is cheaper than running rads and im happy.

    @ Agile, what are your thoughts on piping a radiator into a UFH manifold to reduce chill points around a window? Just an idea i was thinking about?

    Gareth
     
  4. looneyfitter

    looneyfitter

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    What does OP stand for?
     
  5. Agile

    Agile

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    Mr Deuce is the OP or original poster.

    I do like even heat in a room and that means I like wide single panel rads on two adjoining walls. It gives some of the evenness of UFH without all the bother.

    With good double glazed windows and good UFH then rads under the windows should not be needed but I would not complain if anyone wanted to have them. Feeding them from the UFH manifold would introduce timing errors.

    Part of the mindset of long term plumbers is that you fit the smallest rad that might give enough heat and a narrow double is the easest to handle.

    I use the longest single panel to distribute the heat more evenly.

    Tony
     
  6. deuce22

    deuce22

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    Hi.

    I have just looked at the Polypipe Overlay system that picas posted and I'm assuming that after this gets laid down the laminate floor can be installed directly over the top.

    This will allow me to not have to pin the pipe myself, fix the batten and spread the sand.

    Are there any other brands that make similar products.

    Thanks.
     
  7. looneyfitter

    looneyfitter

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    Yes you could use spreader plates between barrons but that would cost more

    @agile

    What type if timing errors matey?
     
  8. DeltaT

    DeltaT

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    You got it Gareth mate, but keep all the dark arts to yourself..................... ;) :LOL:
     
  9. DeltaT

    DeltaT

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    Of course you can put pipes in at any centres you like, the closer the centres the lower the mean water temperature you require, so the cheaper it is to operate.

    As for glazed areas, common practice is to band the pipes closer together at large glazed areas. Rule of thumb; close band the pipes in front of the window, one third the height of the window.
     
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  11. DeltaT

    DeltaT

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    Thanks lcgs an interesting read as always.

    Another thing to consider with UFH; with radiant heat, 17-18*C will feel like 21*C. The human body loves radiant heat.
     
  12. deuce22

    deuce22

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    Hi.

    The reason I was thinking of the overlay system is that it saves all the work.

    It looks as if it gets laid down, pipe fitted and that's it.
     
  13. Agile

    Agile

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    To give a warm room at 0700hrs the UFH will need to come on at about 0500hrs.

    If there is a rad on the UFH circuit then its heat output will be given from about 0505hrs which will be a waste of heat.

    If there is to be a mix of UFH and conventional rads ( which I like ) then the rads are better on a rad circuit with a higher flow temperature and a later time slot.

    Using UFH more for background heating enables the boiler to be more condensing but also get a rather faster warm up from the rads. The rads can also be controlled to off on their TRVs and so better regulate the room temperature as it warms up outside.

    Tony
     
  14. looneyfitter

    looneyfitter

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    Cheers Tony..... I suspected that was what you meant tbh. If you using rads/ufh i suppose you could still bin the TRV and use the original room stat/programmer but then fit an inline valve and timer to the Rad circuit. That way both individually timed but temp contol would be more accurate.

    Sorry to hijack.. Think its relative

    Deuce the way i have spoken about is the same as overlay in therory only cheaper i would imagine...... Would be interested on m2 costs of that stuff
     
  15. deuce22

    deuce22

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    Hi.

    Sorry to keep going on, but as I already said I have to buy a load of materials on Friday.

    I'm having a good deal with the trade department at B and Q and it's all going on interest free.

    I only have until Friday to make out the list and need to know if I'm going for U/F heating or Rads.

    I've just been in contact with someone who has told me to do it in electric instead of wet.

    He has done about 100 m2 in electric matting at 100 w/m2 and says it plenty.

    He has giving me the web address of a company that gives all the tech specs and it seems OK.

    I initially thought that the running costs would be ridiculous, but after reading through this site it states that "A typical new building would perhaps cost around £3-£4 per sqm per annum to run, so 100sqm free floor area home would cost around £300-£400 per year to heat".

    Even if I went overboard and said £5 per m for myself that would cost around £200 per year for the 40m2 I need to cover, costing around £16/17 per month, which is fine with me.

    I'm assuming that in theory whether it's rated to 100 w/m2 in electric or wet they will both give the same results.

    Is this a possibility or should I get it out of my head.

    Thanks.
     
  16. looneyfitter

    looneyfitter

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    IM not feeling elec underfloor heating. Too much to go wrong in my opinion. At least with a wet system you only have to keep your inhibitors up to date.
     
  17. deuce22

    deuce22

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    Hi looneyfitter.

    Is it right that if they are both rated at 100w m2 then they will perform the same, although it will cost more for electric.

    I've now got so much advice that I'm changing my mind all the time.

    Thanks.
     
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