Accurately sizing steam boiler

Ted Robinson

Using various radiator tables I calculate or 2100 sq ft house has 410 sq ft of radiation. Contractors want to install the Burnham IN7, 542 sq ft, 16.7% oversize. I am willing to run a small risk with the IN6, 450sq ft, 9% oversized.
I recognize that there is little downside risk for the Pro's to suggest the larger boiler, and have more to lose in using a smaller unit.

The exposed steam pipes will be insulated. We will not use the new boiler for domestic hot water and we have no plans to expand the house. I think the smaller boiler will be adequate and thus more efficient. FYI: The attic insulation is very good (9 in) and 90% of the 2 x 4 walls have blown-in FG insulation. And if someone replaces the old windows then the existing radiation should be oversized. Is the smaller boiler cutting it too close?

Steamhead (in transit)

Nope

go with the smaller unit. It will handle your system, why buy more than you need?

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Ted Robinson

Thanks to this Site . . . . .

From the years of watching, and Dan's book, I am confident that the new boiler will be a better match than the outgoing oil boiler, that was rated for 640 sq ft!