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Wirsbo Manifold Adjustments

Hi, Looking for some help. Purchased a 20-year house in MN with Wirsbo floor heat in the basement. It has 8 zones. Looking to adjust the manifold to increase heat in some rooms and decrease in others. I read that the initial setting (mid-point) is a dime above the brass collar. Is it correct that screwing the black disk on top of the manifold down all the way will open the zone up completely and conversely, screwing the black disk on the top of the manifold up all the way will close the zone completely? This seems backwards to me, plus, my threading is about 1/2 inch, so a dime does not appear to be midway. Can anyone offer me some advice. Thanks in advance!


  • Big Ed_4Big Ed_4 Member Posts: 1,433
    edited October 16
    Yes , I would first make sure the manifold is piped correctly . Most are installed incorrectly . It should be piped reverse return , Meaning ...The first loop out should be the last to return . Post photos of manifolds and label each loop . Piping it incorrectly is a Normal mistake
    I have enough experience to know , that I dont know it all
  • GroundUpGroundUp Member Posts: 1,034
    There is absolutely zero reason for reverse return piping with radiant manifolds. None whatsoever. If there were even the slightest bit of pressure drop (there never is), that's why we have balancing valves. Reverse return is a complete farce and waste of time in this regard.

    To the OP, yes you are correct with how the loops adjust. Do your manifolds have the glass flowmeter globes on top? Some do and some don't. Without flowmeters, it's really just a crapshoot unless you know the exact length of each loop. You can start by cranking in the valves on the zones you want cooler by a turn or so, and waiting a couple days to see how it responds. It may take weeks to get it dialed in, but there's not much other choice that I'm aware of without flowmeters
  • hot_rodhot_rod Member Posts: 13,833
    When we talk reverse return on radiant manifolds, it is merely staggering the loop connections. So the first loop fed, is the last returned. Really over a very short manifold trunk dimension it is probably not a huge deal.

    Ideally a load calculation and radiant design would indicate where to set each balance valve.
    Or as you suggest, adjust to your needs or liking. That is one of the beauties of hydronics, very adjustable.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • rileyrealestaterileyrealestate Member Posts: 2
    To the responders, thank you. Just 2 basic questions. The black top disk (no glass flowmeter globe). Is it correct that if I turn it clockwise or crank it down to the brass collar, it opens it up completely? Conversely, when I turn it counter-clockwise or crank it up from the brass collar, it closes it completely? Secondly, I read that a midpoint is 1 dime width above the brass collar, is that correct? This is a 21-year old Wirsbo system with 8 zones (16 hoses), heating about 2,500 sq. ft. in the walkout basement level. The central heating has supplemental vents in the ceilings. Thanks again.
  • Big Ed_4Big Ed_4 Member Posts: 1,433
    edited October 18
    All parallel systems should be piped reverse return .
    I have enough experience to know , that I dont know it all
  • MikefromMnMikefromMn Member Posts: 1
    On my Wirsbo manifolds, they are open when turned counterclockwise(loose). No flow meter on my old brass manfold. Newer EP (plastic) manifold has flowmeters and turned in (clockwise) is closed.
  • TAGTAG Member Posts: 276
    I have always questioned the notion of reverse return -- has there ever been any real world study of this ? My memory of fluids class (not prefect) ... seems to say that with proper circulator ... flow /head -- this is not happening.
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