old farmhouse boiler size

nogomomo

Installing new boiler in farmhouse. Tore out old gravity feed 2 " lines, that have a circulator on now. 175k new yorker 30 yearold being removed. New windows, blowing insulation in most walls and adding r-19 to attic. 2300 square feet with 1 wall adjoining other half of house. Still will be an old farmhouse with some infiltration, installing condensing boiler, 10 degree outside, will 30 to 150 be too big, or 30 to 120 do the job? Baseboard cast iron first floor, cast iron uprights on 2nd floor

SWEI

I would be shocked if 2,300 square feet needed more than 60-70k maximum at design conditions. You really need to do the heat loss calc. Really.

nogomomo

i was running a heat loss program and coming up in the 60k range, I could not imagine it would take one that big. the house did not have insulation on a lot of it at one time. thanks

SWEI

Trust the math. Look for a boiler with a minimum firing rate under 20k. 15k would be even better.

Jamie Hall

As has been said -- trust the math. First place, the old boiler may well have been oversized. It has happened... second place, if you blew insulation into the walls, you went from R4 (maybe!) to R10 or 12 for the walls. If you really got R19 in the attic, you went from R4 to R19. Both of these are big changes.

deomair

second place, if you blew insulation into the walls..

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OMAIR