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Pipe/Manifold and Circulator Sizing
I have an old, hacked up single zone mono-flow system feeding cast iron radiators in an old two-story farmhouse I recently purchased and I am hoping to convert to a two zone system, one for the first floor and one for the second. There are seven radiators on the first floor and seven radiators on the second floor. I am planning on two sets of manifolds, a "send" and a "return" for each of the two floors, PEX from new manifolds to 1/2" copper that is currently feeding each radiator (individual home run) already piped through the floors and walls. It has been recommended that I control zones with individual circulators, not zone valves.
Boiler is a conventional oil-fired 100k Burnham.
I am looking for some guidance regarding pipe and circulator size...
If my math is correct....
Calculating flow rate from BTU/EDR calcs (20deg delta T), adding-up GPM requirements of all radiators per floor (zone), I will need approximately 6.5GPM for the first floor zone and approximately 5.5GPM for the second floor zone. Boiler IN/OUT piping is 1.25" which I believe can supply 16gpm. My thought is to "T" two 1" manifolds off of the 1.25" boiler supply, 1" manifolds able to carry 8GPM each, I believe. These 1" manifolds will then be feeding 7 radiators each via 1/2" PEX requiring 6.5gpm first floor and 5.5 GPM second - which I believe will be enough flow.....
Finally I am not sure about calculating total head-feet to make a fairly accurate circulator pump selection. While piping and fitting data is available I'm sure, how would I calculate for these radiators?? I have two Taco 007's I can reuse from the old system if applicable.
Any help provided is much appreciated, as I am hoping to make any mistakes on paper, not in practice...