A. In a steam system, the boiler is not sized according to the calculated heat loss of the building. Instead, it must be sized according to the number of square feet of installed radiation. Tables that give the equivalent square feet of radiation are available for most old radiators from the Hydronics Institute (P.O. Box 219, Berkeley Heights, NJ 07922; 908/464-8200). A new radiator should include that size in the specs. Steam boilers normally carry a specification plate that gives the number of square feet of radiation the boiler can supply.

If the boiler is sized according to the calculated heat load, it will not supply enough steam to reach the far end of the system without condensing first, and the system will never work properly. This is a common problem when conversion burners (gas or oil) are installed in old coal-fired boilers. The burner must be large enough to generate the...

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