sizing a distribution manifold

roundrightfarm · September 2016

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?

hot_rod · September 2016

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?

roundrightfarm · September 2016

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 · September 2016

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.

roundrightfarm · September 2016

thanks hot rod for clearing that up

sizing a distribution manifold

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