sizing a distribution manifold

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roundrightfarm
roundrightfarm Posts: 54
in Radiant Heating
I'm install a boiler with home run distribution, going to 23 radiators, all with TRVs. I'm look at two 13 outlet manifolds. I have the option of 1" or 1 1/4". The price difference is minimal. Design heat loss is 141k BTUH, giving me a flow of 14 GPM at design conditions (delta T = 20), or 7 GPM through each, assuming they are well balanced. So 1" seems more than adequate for my flow, but given that 1 1/4" is basically the same price, are there any other considerations that would make me choose one or the other?

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  • hot_rod
    hot_rod Posts: 28,516
    I don't know what brand you are considering, sometimes only the connection or ball valve on the end changes, same manifold dimension really. So the 1" should cover your load of 7 gpm.

    Branches are usually good for up to 2 gpm, will that cover your largest radiator?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • roundrightfarm
    roundrightfarm Posts: 54
    Thanks hot rod. I'm looking at Caleffi. Do know if it is the case with these that only the connection threads are different?

    My largest radiators should have a flow around 1GPM
  • hot_rod
    hot_rod Posts: 28,516
    Correct, manifold is identical, just the valves on the end change. The manifolds are unique with a recess for the tubes to lay in, plenty of flow with the square shape.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • roundrightfarm
    roundrightfarm Posts: 54
    thanks hot rod for clearing that up

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