Sizing Cast Iron Radiators

Although a new installation of cast iron radiators is rather rare today, a large number of hydronic and steam heating systems using this nearly indestructable form of radiation remain in service. In many older homes, extensive alter- ations to flooring and trim woodwork would be necessary to install a modern baseboard or convector heat system. A contractor is often called upon to upgrade a radiator system with the installation of a modern boiler, and some special considerations should be noted in determining the correct heating capacity. If the home’s original boiler is still in place, it may be old enough to have been a coal-fired unit converted to gas or oil operation.

To better calculate the system’s capacity, radiators can be sized by using the tables shown below. The output of a radi- ator is measured in square feet of radiation, determined as follows:

1. Measure the height and width of the radiator. 2. Count the number of columns or tubes in a section. 3. Count the number of sections. 4. Read number of square feet per section from tables below. 5. Multiply by number of sections. (this gives total square feet) 6. Calculate BTUH by multiplying the appropriate emission rate by the total square feet. (obtained from step 5)

HEAT EMISSION RATES FOR CAST IRON RADIATORS

Output Average

Water Temp. 170

175 180 185 190 200 205 210 215

BTU per Sq. Feet

150 160 170 180 190 210 220 230 240

COLUMN STYLE RADIATORS

TUBE STYLE RADIATORS

38"

We can supply new radiators upon special order in several styles and capacities to cover most requirements. Contact your R.E. Michel Company sales representative or local branch for more information.