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Thread: Manifold Sizing

  1. #1

    Default Manifold Sizing

    I've got a question to something I can't figure out and would appreciate any help here.

    Sizing of intake and outtake manifolds on a 3 zone series loop, HW boiler with 1 pump and 3 zone valves.

    Here's my concern. The pump (B&G 100) has an opening of just less then 1". Since that is the case, does it make sense to build to and out of it with anything larger then 1" pipe? Is it necessary to use 1 1/4" or even 1 1/2" when the pump restricts it to 1" ?

    On the other side. The 3/4" zone valves have an opening that's about 3/8" at best. Does that manifold that, in this case, feeds 3 small zones (it's a small house) need to be larger then 1" ?

    Sibi

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default heating

    The B&G 100 has multiple size flanges from 3/4" to 1 1/2" and the pipe size is determined by the demand, not the opening in the pump. The same with the zone valves.

  3. #3

    Default

    HJ,

    Thanks for the quick reply. How would I arrive at the demand size for a given system? Is there such a thing as a chart to reference?

    Sibi

  4. #4
    Master Plumber nhmaster's Avatar
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    I usually keep the manifolds the same size as the boiler tapping untill after the circulators.

  5. #5

    Default

    Keeping the manifold the same as the boiler tapping is a safe bet because then it cannot be too small or at least it cannot be made larger on that boiler.

    With 3 small zones and even with this small in output BTU's, this boiler has 1 1/2" tappings.

    To keep/make the Delta T at the correct level, would you use flow valves on each zone to regulate this? Or is that something that should always be done?

    Sibi

  6. #6
    Master Plumber nhmaster's Avatar
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    Yes, purge and balance valves are always a good idea. Nobody ever puts thrermometers on the individual returns but doing so can really be interesting. We usually only do it for radiant though.

  7. #7

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    Thank you for the advise. I think I'm fairly well set with this job and while I'm getting this done at dead slow speed I should be ready to fire this up early next week.

    Thanks again,

    Sibi

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