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S plan vented to S plan Unvented

Discussion in 'Plumbing and Central Heating' started by 24hrcallout, 6 Jun 2021.

  1. 24hrcallout

    24hrcallout

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    Good evening all, I’m a drainage engineer with a plumbing background. My property is an old 1930’s, has an indirect vented cyclinder, f+e in loft and also water tank storage in loft. Would like to replace the vented with an unvented. Same location as existing, really good mains pressure on 15mm. I’m going on a G3 course in two weeks so I can do my own...legally...I have an ideal logic H24 boiler. Is this a case of removing the F+e tank in loft and tank water storage tank, connecting new cyclinder in its place, but adapting pipework with the flow and return into megaflo and no longer in loft. Megaflo has the vessel inside right? So instal prv and the two Honeywell valves stay in same place. And I will also cut out the Stuart Turner pump for shower pipework

    Read more: https://www.diynot.com/diy/threads/changing-vented-s-plan-to-unvented-s-plan.572423/#ixzz6x25Cqxeq
     
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  3. polesapart

    polesapart

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    No indeed.

    Moving from vented to unvented cylinder and converting an open-vented heating system to sealed are two different animals.
     
  4. fixitflav

    fixitflav

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    To convert the primary side to unvented you also need an expansion vessel. But be aware that in a property this old you might get leaking pipework due to the higher pressure.
     
  5. Mottie

    Mottie

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    Surely it’s more to do with the age of the existing heating system than the age of the property? The existing system may only be 20 years old.

    Having said that, we converted ours from vented to unvented hot water and open to sealed heating and had a couple of leaks on two of the original remaining three steel rads that had been fitted in the 1960's. No leaks from any of the pipework though. I changed all three rads.

    They adapted the hot water pipes in the loft after removing the two tanks by just connecting the feed to the F&E tank to the outlet from the cold water storage tank.
     
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  7. Hugh Jaleak

    Hugh Jaleak

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    Lot more to it than you're suggesting. F&E Cistern feeds the Primary sides, if you're sealing that, you need to make sure Rads and pipework will hold the higher pressure, suitable expansion vessel, Pressure relief etc are fitted and indeed, the boiler is safe and suitable to be pressurised.

    Unvented merely replaces a Vented Hot Water Cylinder and the associated cold storage cistern in the Loft. You need a G3 to install and/or work on these systems due to the need for additional safety systems required for pressurised hot water.
     
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  8. Agile

    Agile

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    Some prefer to keep the loft tanks to supply toilets otherwise the float valves need to be changed to high pressure types.

    The cold supplies to showers ( and really baths too ) need to come from the new unvented cylinder to ensure the pressures and flow characteristics are similar.
     
  9. Mottie

    Mottie

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    Yeah, I had to change the float valve in our downstairs loo.
     
  10. ianmcd

    ianmcd

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    you do not have to change the valve, simply the pressure insert , 2 min job at most
     
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