Gravity fed heating

Discussion in 'Plumbing and Central Heating' started by smashit, 2 Jul 2011.

  1. smashit

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    Hello again good Forum. :D well its been a year since i was on here for advice :oops: ....anyhow i need advice on a central heating system......Firstly i have just bought a single storey cottage in the Mountains of Romania now here is where the problem is NO ELECTRIC.......so i want to install a woodburner with back boiler and 3 radiators (no hot water tank) :eek: so what i need to know is can i install this with no pump....the header tank would be directly above the fire some 7ft ....am i also correct in thinking i would need to use 22mm copper throughout the system.....and how reliable as a system is it :?: thanks in advance
     
  2. Servotech

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    It's possible, but things have now moved on from the days when gravity ch heating was
    installed.
    Things you will need -
    22mm pipes all round - yes no problem.
    x3 3/4" tapped out radiators - very hard to get hold of these days.
    x6 3/4" - radiator valves - again very hard to find.

    Requirements for gravity circulation -
    Header tank at least 1m above the highest radiator.
    A rise (or level at least) on all flow pipes leading to each radiator.
    A fall (or level at least) on all return pipes from radiators returning to boiler.
    Though you are allowed a small dip on the return it's something like 1/10th of the circulating height (making a underfloor return possible).

    If you can source the materials and meet all the requirements then it will work very well forever more (nothing to go wrong)!
    Good luck,
    servotech,
     
  3. smashit

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    Many thanks for the swift reply, may i ask would any benefit be gained by having the hot send pipes in the loft (lagged) and dropping down to each rad ? the cold return at floor level ?
     
  4. Servotech

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    Sounds like you're using the old one pipe system.
    A good old fashioned way of doing it and you can use the allowed (1/10th of circulating height) dipped return to connect the return at floor level up to the boiler.

    The Expansion/feed tank will need to be (at least 1m) above the heating flow in the loft and the expansion pipe taken from the flow at the highest point will also act as the vent.

    Use straight not angled radiator valves on the flow to each radiator.
    A valve on the radiators return is not really needed on this system.

    It will all work fine, the only problem is sourcing the materials in 2011. There's no demand so no-one bothers to manufacture them!
     
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  5. smashit

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    I was pondering on the one pipe system as i will be adding antifreeze to it for when the property is left alone.....Its good to know that the one pipe system works......as far as getting the fittings that is no problem in Romania (they are not as modern as us) Lots of good old second hand school type rads around for about @ £1 each LOL.......I am building a Russian masonry fire (why we dont have them in UK i dont know) but inside i will fit two boiler jackets to supply the 3 rads only........Can you reduce down to 15mm at the Rads or will that reduce the flow too much.
     
  6. Agile

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    Perhaps I am wrong and if so some of the old boys will correct me.

    But this is a SINGLE story cottage!

    I dont think there is enough vertical height to get any significant gravity flow going with normally used pipe sizes.

    If you calculate the gravity head in a two story building with a 10 C delta T then its more like just 0.1m
     
  7. smashit

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    Hello
    thanks for your reply.....It is a cottage and i have a max of 2.5 m up from the boiler poss 3m max is that enough ?
    thanks again and sorry to be a pain but i need to get it right first time
     
  8. Terrywookfit

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    If you have 1m head above the flow / vent pipe in the loft it will be fine. If the rads are not too large 15mmm will be ok.
    Use swept tees for the drops if you can.
     
  9. Servotech

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    [



    I was pondering on the one pipe system as i will be adding antifreeze to it for when the property is left alone.....Its good to know that the one pipe system works......as far as getting the fittings that is no problem in Romania (they are not as modern as us) Lots of good old second hand school type rads around for about @ £1 each LOL.......I am building a Russian masonry fire (why we dont have them in UK i dont know) but inside i will fit two boiler jackets to supply the 3 rads only........Can you reduce down to 15mm at the Rads or will that reduce the flow too much.[/quote]


    £1 EACH!!! That's really cheap and they sound just the job.
    I cannot recommend reducing down to 15mm to the rads for the reason that you have mentioned - gravity needs large pipes and no restrictions (hence the 22mm radiator valves I've recommended) going down to 15mm would be asking a lot.
    On the other hand increasing the size of the heating main to 28mm would be a plus.
    I'm afraid you've got me with the term boiler jacket! :)
     

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