When replacing an old boiler, adding a radiator or changing one, you need to know the heating capacity of the radiators connected to your central system. The heating capacity is measured in British Thermal Units (BTU) and it’s determined based on the surface area of the radiator, measured in square feet and it’s influenced by the set water temperature of your boiler. Below you will find out how to calculate the capacity of hot water or steam radiators.
Determining the Heating Capacity of a Radiator
The heat output of cast iron radiators, historically referred to as Equivalent Direct Radiation (E.D.R.), depends on the water temperature running through it. If you refer to the table below excerpt from the book Short Course in Modern Heating by Garnet H. Hopper, published by AGE Publication LTD, 1951, you will find the heat emission in B.T.U. at a given water temperature.
Example Calculation
For this example we will work with a water temperature of 160°F and a Peerless radiator 38in tall, 2 columns with 8 sections.
The B.T.U. emission at 160°F water temperature is 130 B.T.U.Â
Referring to historical manufacturer data below;
the Peerless radiator  38 inches tall, with 2 columns and 8 sections has a heating surface of 32 square feet.
The heating capacity of this radiator is : 32 sq. ft. x 130 B.T.U./sq. ft. = 4160 B.T.U.
Simplified Calculations with Precompiled Charts
To simplify this process, Ecorad has compiled historical data into easy to use tables. These provide the B.T.U equivalent at various operating water temperature per section of radiator. If you refer to the table below:
The same Peerless radiator with 38 inch tall with 2 columns has an output of 520 B.T.U. per section. Than for eight sections, you get: 8 sections x 520 B.T.U.= 4160 B.T.U.
Download our technical specifications booklet including these tables.
Why Choose Ecorad for the restoration?
Ecorad’s expertise blends sustainability with respect for heritage design. We optimize energy efficiency while preserving the charm of vintage craftsmanship. Our meticulous work ensure you receive a product that performs reliably and sustainably.
Learn more on ECORAD’s Restoration Process.
For more information on radiator visit ecoradinc.com !Â
More calculations:
How to calculate the capacity of radiator for an electric conversion
How to calculate the capacity required for your rooms, just scroll down this page to our calculator.
