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Posted by Eichler on June 19, 2006 at 17:48:15:
My 2,250 sq.ft. 1969 Eichler home near San Jose Ca has a 117K BTU inlet 97K BTU output natural gas Raypak boiler with a single 1/6 HP circulation motor driving 10 radiant concrete slab loops - one/room. It has 500 sq. ft of single pane glass with lined drapes in the living room, but other rooms are R13 walls and R20 ceiling and double pane. The 117K BTU Raypack takes a long time to get the house up to temperature when we get home from work. Winters are mild, 30F is cold. It runs constantly for several hours before the water hits the 135_F limit, and for this reason I was considering getting both a higher efficiency and a modestly higher BTU rating gas boiler. I do not know if the pump size is affecting efficiency. No one is home during the day, so the system cold starts just before we get home.
I would appreciate information on proper sizing estimates of the boiler and pump, plus any data on quality and reliability between what looks to me like the two top designs: the Munchkin 140 and the Weil-McLain Ultra 155. Both are condensing boilers with ~92% AFUE.
I've had two reputable radiant heat companies give me completely different recommendations.