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Discuss Changing to pressurised system in the Central Heating Forum area at

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  1. Stants

    Stants Member

    Hi I'm thinking/ wanting to change
    From a Vented to pressurised
    I understand a few basics ( CW tank goes + Cylinder, Pump,gate valve goes
    Replaced by a mega flow or similar ) the boilers in kitchen and cylinder in bathroom ( directly above Boiler on 1st floor ) I'd like to move everything into the loft
    1 is there a huge amount of pipe work that needs changing ?
    I know I need a gas supply to go up and upgrading of the cold water supply into the loft I've done a check on the pressure it's just under 4 bar as it is ( I will upgrade if necessary though ) I've got more to ask ( sorry )
    I'm guessing / hoping there's a few q,s I need to explain
    Ps I've a good route for any additional pipe work to go up where the existing is now
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    What's your litres per min ?
    • Like Like x 1
  3. Ted808

    Ted808 Plumber GSR

    Is that static pressure?
    Ditto Shaun
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  4. steadyon

    steadyon Active Member

    1. As stated above you need a good dynamic cold water pressure (I'd suggest 2 bar minimum) and a good flow rate (20 litres / minute) or better.
    2. Shouldn't be huge pipework changes. You'll probably need to change the cold water rising main from 15 mm to 22mm, a provide a 22mm hot feed back to the connection point in the old airing cupboard, increase the size of the gas pipe and re-route it, and you'll need outside access for the "D2" pipe from the unvented cylinder. You'll also need to make new arrangements for the condensate pipe from the boiler.
    3. If you are planning on moving an existing boiler into the loft, make sure the necessary flue sections are available and the length compliant with manufacturers allowance. Your gas safe registered (GSR) installer will advise. You can't do any of the gas or flue work yourself unless you are GSR.
    4. Be aware of the regulations for boilers in lofts, proper flooring, proper ladder, guard rails.
    5. The unvented cylinder will probably weight at least 1/4 of a ton when full. It needs to be properly supported and in a place which can take the weight.
    • Like Like x 1
  5. Stants

    Stants Member

    The flow I filled a bucket for 10 seconds
    The amount was 3.3 Ltrs so 3.3 x 6=19.8 in 1 minute I think that's how it's calculated or is that a bit Heath Robinson lol
  6. Jim Goodenough

    Jim Goodenough Plumber

    Small point Stants,
    do you have any gravity/manual showers (fed by hot & cold services)? If yes, check out it's/they're compatible with an unvented system.
    • Like Like x 1
  7. Stants

    Stants Member

    Yeah I do but will be redoing existing bathroom at the same time
  8. SimonG

    SimonG Trusted Plumber

    I'd be more interested in the dynamic pressure.
  9. Stants

    Stants Member

    Hi all the tests I've done were at the Kitchen tap downstairs I've heard / read that taps greatly reduce/ restrict the flow I need to check but think the mains at the mo is only 15 mm so was found to change this to 22 mm do you think / feel this would surface at least to try to see if it was enough if not would upgrade from the street ( trying to avoid if possible i.e. Digging up garden etc
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