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Help with Sizing a Boiler
Hi all. Am new to heating help and new to steam heat in general. Could anyone give me some input into sizing a replacement boiler for a parallel flow one-pipe steam system? I live in a 1932 home currently with an American Standard oil burner (maybe from 1975?) and am in the middle of a gas conversion.
Current EDR = 407.5 sq ft (my contractor measures 427 sq ft).
Pipes are NOT insulated but I plan to insulate the mains.
There are two caps off the mains to suggest old radiators that were disconnected but they're capped at the mains.
407.5 x 240 x 1.33 pick up factor (assuming a reinsulate the mains) = 131 MBTU D.O.E.
My contractor is using a 1.5 pick up factor because he states that even though I reinsulate the mains, the rest of the pipes in the walls are not insulated. So his calculation would give a DOE = 147 MBTU.
My contractor therefore recommends a Weil McLain EG-55 Steam which would give a DOE=167 with a net IBR=125 and so can handle the 147 MBTU load. He thinks that even though it's slightly oversized, it's not so much that short cycling will not be a problem.
I noticed that the Weil McLain EG-50 Steam has a DOE =145 with a Net IBR=109.
I have three questions:
1) Is it true that the pickup factor of 1.5 is needed even if I reinsulate the mains since the pipes in the wall remain uninsulated?
2) If a pickup factor of only 1.33 is needed, will buying the EG-55 still be okay; in other words will I not have to worry about short cycling and ineffieciency?
3) Even if I need to use a pick up factor of 1.5 and I need to heat a system requiring 147 MBTU, would it be just as good to still go with the smaller boiler (EG 50 capable of delivering a DOE of 145) so that I get long heating cycles with radiators that are slowly heated (I'm thinking of Dave Brunnell's article, "Taking Another Look at Steam Boiler Sizing Methods")?
Thanks to all for all your contributions on the wall. Learning about this stuff is addicting.
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