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Drain Down and Refill Combi

Discussion in 'Plumbing and Central Heating' started by pdfctu, 15 Mar 2005.

  1. pdfctu

    pdfctu

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    Really could do with some help.
    Have to drain down central heating which uses Combi Boiler, so no header tank. Can anyone explain step by step of wot to do and where to find things (keep reading bout filler loop? / and air vents and ensuring getting air out of boiler etc)
    thanks in advance

    Also refill process - thanks
     
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  3. drip

    drip

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    why do you need to drain it down what make of combi is it and model
     
  4. pdfctu

    pdfctu

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    Presume I need to drain it down to move a n area of heating pipework for radiator - not moved in yet so dont know the make or model - I stupidly assumed that the drain / fill procedure would be the same for all Combis (sorry) should i find out first or can you help with a general gide
     
  5. kevplumb

    kevplumb

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    1 find drain cock
    2 attach hose and open same
    3close drain cock
    4 now the fun start's
    5 refill and vent system (silver braided pipe under boiler )
    6post when you hit a snag ;)
     
  6. PEDANTICVINDICTIVEMAN

    PEDANTICVINDICTIVEMAN

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    1 make sure boiler is off at the electric main so boiler wont try to fire up.
    2 find drain cock
    3 fit hose and open cock, hope washer doesnt't stick.
    4 open all air vents on radiators to let air in so system will drain properly.
    5 carry out pipework alteration.
    6 close all air vents on rads.
    7 put recomended rust inhibitor in system via a radiator.
    8 fill system as per boiler makers instructions and open any air vents asked for..
    8 vent all radiators.
    9 switch on boiler and be ready to switch it off quick if it starts banging due to air lock and overheating.
    10 pay yourself £40.00 an hour
    11 let us all know how you get on so we can all laff at you.
     
  7. pdfctu

    pdfctu

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    Thanks for your help so far. Will let you know.
    You mention air locks etc, and banging, is this down to radiators not bled properly, or is there more to it (or again does it depend on make of boiler)
    Thanks again
     
  8. ChrisR

    ChrisR

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    It being a pressurised system you shouldn't have trubble with air locks.
    Instead of opening/draining all the rads, you could shut their valves so you keep the water in. Then you only need to drain the pipes, and one rad ( eg by the drain cock) so flow and return from the boiler are connected. There will be an auto air valve on the boiler, which should always be open. Its position depends on the boiler.
     
  9. PEDANTICVINDICTIVEMAN

    PEDANTICVINDICTIVEMAN

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    Yea but no but yea but no but, half the time the auto air vents on the boiler are seized and the boiler wont vent properly hence the banging because the boiler isn't vented, ooooohhhhhh aaaaaahhhhhhhh ooooohhhhhhhhh aaaaahhhhh missis, oh please yourselves.
     
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  11. pdfctu

    pdfctu

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    Thanks to all for advise - can i just recap to ensure I have it right
    1. turn off stop cock
    2. turn off boiler at switch next to it
    3. turn off flow and return valves if it has them
    4. ensure auto vent on boiler is open???
    5. close off all rads
    6. drain off from lowest rad with drain off.
    7. close drain off
    8. do work.
    9. turn on stop cock.
    10. turn on flow and return valves. (now wot with auto vent??)
    11. open filler loop?? to fill system (to wot pressure before turning off)
    12. open rad valves. - bleed /vent rads (downstairs first or second??)
    14 re open filler loop (continue filler loop and bleed until all rads done?)
    15. wot should final pressure be before turning on boiler.
    16 turn on boiler?

    really sorry to be so naive, but a final check of my checklist would be a great help - thanks all again
     
  12. kevplumb

    kevplumb

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    1 no need
    2 yes
    3 no real need
    4yes
    5yes both ends
    6 yes
    7 yes
    8 yes
    9 no need
    10 no need
    11 yes pressure to app 2 bar to vent
    12 yes the only air will be in the pipework so run the system before venting
    14 yes
    15 1.2 cold
    16 bleed pump
    17 it help's ;)
     
  13. pdfctu

    pdfctu

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    thanks kevplumb - re stop cock - does that mean that no water can get into the heating pipes untill the filler loop is opened??

    where do i find the auto vent on boiler and wot does it look like?
    when i have refilled the pipes but not opened rad valves you said run the system. do you mean switch boiler onto run heating, or something else?
    should i bleed up or down first, and how do i bleed pump

    so sorry !
     
  14. kevplumb

    kevplumb

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    yes no water gets in till you open the loop

    auto air vant looks like a little black bottle with either a red or black valve type cap on

    open the rad valves then bleed the air that will push into the rads then run the heating for a bit

    up or down dont matter with a pressurised system

    big screw in the middle of the motor casing

    dont be ;)
     
  15. pdfctu

    pdfctu

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    thanks a million - will let you know how it goes
     
  16. Daz-

    Daz-

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    Hi

    Do you have to bleed pump in a combi boiler?
     
  17. ChrisR

    ChrisR

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    NOt normally but it's hardly worth asking - it takes 2 seconds!
     
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