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Discuss Reverse circulation new build in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Jeff

    Jeff New Member

    Hi,
    I'm looking for a little help. I bought a new build and have heating issues since we moved in. The builder wants the installer to resolve the issues, but hes been back now about 5 times and still the issue persists. I was hoping for a little advice. We have 2 circuits 1 upstairs and 1 downstairs. When the downstairs is on the rads upstairs start getting hot one by one via the return. Whats the best way to get to identify whats causing the issue. Is this issue generally caused by the way the pipes have been run i.e. 22mm to microbore or is it generally the pipework around the boiler. I'm reluctant to pay someone to resolve it, as its the builders responsibility but the plumber the builder keeps sending (the installer) is not fixings the problem and seems to not be able to identify the issue either. Any help or direction would be greatly appreciated.
     
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    It's the plumbers fault for teeing in the returns wrong

    What system do you have combi or unvented eg cylinder ?
     
  3. Stigster

    Stigster Plumber

    Plumber needs to abide by the "Three Tee Rule". This thread covers it fairly well I believe.

    3 tee rule anyone?
     
  4. Jeff

    Jeff New Member

    It’s an unvented cylinder and Worcester condenser boiler. I could post a photo of the pipe work near the boiler tonight if that would help identify. I’ll be honest there are. Lot of pipes coming and going
     
  5. Stigster

    Stigster Plumber

    Photos would be helpful almost certainly. If I can't work out the problem somebody here will. They are a good lot.
     
    • Like Like x 1
  6. johnduffell

    johnduffell Member

    If the installer understands gravity they should be able to work it out. If there's hot water below cold in a vertical pipe, they will start to mix even if no circulation.
    Agree that photos would help, ideally annotated with which pipe is which if not clear.
     
    • Disagree Disagree x 1
  7. Jeff

    Jeff New Member

    Thanks everyone. I’ll take a photo and post tonight. Your help is much appreciated!!
     
  8. fixitflav

    fixitflav Member

    But it's not gravity or convection that causes this problem. All the CH return pipes must be commoned before the HW cylinder return comes in. My first house in 1973 had it, the builders/plumbers had piped it wrong. Got them to change it and everything OK.
     
    • Like Like x 1
    Last edited: Jun 5, 2018
  9. johnduffell

    johnduffell Member

    Oh right maybe i misunderstood it then! So what does cause it?
     
  10. fixitflav

    fixitflav Member

    What happens if it's piped wrong is the HW return entering the other pipe has 2 ways to go - the "right" way, to the boiler, or the other way, through one set of rads in the reverse direction, then the other set in the forward direction and back to the boiler. If you do a sketch you can easily see it.
    I think that's the most likely explanation for what's going on here. A schematic, or a photo if the pipes are identified would be useful.
     
    • Informative Informative x 1
    Last edited by a moderator: Jun 5, 2018
  11. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Is it a 2 port or 3 port system?
     
  12. johnduffell

    johnduffell Member

    interesting, so upstairs has a closed zone valve, but somehow the backflow through the upstairs circuit can get through to the boiler by going forwards through the downstairs circuit (a second time?)

    I'm even more confused, and I'm not quite sure what diagram to draw, but I'd agree the piping would be seriously messed up to have that kind of flow.
     
  13. johnduffell

    johnduffell Member

    having read your original post, your 1973 system was different and had two heating loops on one zone but teed in separately. In this case the OP has two heating circuits on two zones, so that circulation wouldn't happen.

    From reading your description, your system could indeed have also suffered from convection on top of the circulation you mentioned, as the hot return from the DHW side connected with a vertical pipe going back to the upstairs rads:
    "The boiler is in the kitchen, ground floor. The return from the HW cylinder comes down from the ceiling. The common return from the upstairs rads also comes down from the ceiling. The common return from the downstairs rads comes up from the floor. Originally the upstairs rads return and the HW cylinder return were commoned, then the downstairs rads return came in - problem! Modified to common the rads returns, then the HW cylinder return comes in​
    "
     
    Last edited by a moderator: Jun 5, 2018
  14. Jeff

    Jeff New Member

    Hi All,

    Here is a photo of the pipework. I've labelled everything that is labelled on the pipes. Any ideas if there is an issue here?

    IMG_8900.jpg
     
  15. fixitflav

    fixitflav Member

    I think the pipe labelled Return is upstairs return. I can see where the HW cylinder return comes in, below the boiler. No pipe is labelled Downstairs return, but my guess is it is off the photo to the right. I can just about see a tee right on the edge of the photo. If that's it, that's the source of the problem, IMO.
     

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