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Discuss Feed and Vent fun :DDDDD in the Central Heating Forum area at UKPlumbersForums.co.uk.

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  1. fixitflav

    fixitflav Member

    I would guess they are old systems. I bought 1st house in 1972 which was piped like that, but it was going out of favour vs boiler - open vent - cold feed - pump then or shortly after, due to the issue of seesawing causing aerated water entry. I modified it, and piping was simpler as the cold feed point was then directly below the F/E tank.
     
    • Like Like x 1
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    No it wasn't as it would be under neg pressure

    Can't get the vent and feed before pump unless it's on the return as it's an ab roof, which isn't the best as it won't vent if the boiler boils

    It's a bloody catch 22
     
  3. fixitflav

    fixitflav Member

    Not sure I understand that. It won't be under negative pressure if the cold feed is on the pump suction pipe.
    Hard to say without knowing the details. You've clearly looked at lots of options so it's unlikely I can add anything, but I'm game to try if you want, no doubt others here will too.
    The bit about the boiler boiling - is it solid fuel? I didn't think boiling was an issue with gas or oil, as there are control and limit-stats.
     
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    it would go

    pump on return pushing into boiler
    feed on flow
    vent on flow

    there is an always risk in certain circumstances eg if a stat goes bad etc
     
  5. fixitflav

    fixitflav Member

    I'd be a bit nervous with that arrangement. I did sketch below based on some assumptions:-
    Pump DP 8m, total system loss 8, 3m across boiler, 5m across rads and pipework
    TWL in F/E tank 3m above fill point on pipe
    Boiler, pump and rads are all at same level
    Shows pressure -2m after the rads. The assumptions won't be spot on and it could be refined to allow for different levels, so it might be OK in practice, specially if it's a tall building so plenty of head from the F/E tank. On the other hand, it might be worse.
    upload_2018-7-8_20-38-39.png
    What precautions are normally taken which you can't do on this job? I'm curious because it might apply to my house!

    PS I hope you're charging the customer double time!
     
  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    tbh these days seal the system unless its ropy like the one im doing

    and some boilers have flow switches in dont fire unless theres flow
     
  7. Vee

    Vee Plumber GSR

    Why not seal without pressurising. Use the header as top up, with gate and non return fitted. Sealed system controls as required with heat only or system boiler ( Worcester Cdi used to not need minimum pressure to operate, but check with them).
     
    • Agree Agree x 1
  8. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    thats not a bad shout would the non return open tho also would need a prv
     
  9. Vee

    Vee Plumber GSR

    Non return is to stop the water backing up into the header. Therefore system controls required, i.e PRV and expansion vessel required either external or internal to boiler (system). Doesn’t need filling loop as header acts as top up vessel. Works a treat without stressing existing pipe work. As the system is sealed and there is no open vent non return will stay shut as for air to get in water would need to get out.
     
  10. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yea but would it open under gravity and not stick
     
  11. Vee

    Vee Plumber GSR

    See edit above.
     
  12. Vee

    Vee Plumber GSR

    Have got two systems like this operational now in their sixth year and no problems.
     
  13. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    head of the tanks vs the position of check?
     
  14. Vee

    Vee Plumber GSR

    Top of system for header. Followed by gate or lever in downfeed, so you can turn system of and for easy replacement of check valve. I positioned them in airing cupboard. Check valve can be anywhere between isolation valve and where it tees into the system.
     
  15. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Trying to work out how much head you have
     
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