Calculating BTUH Output for Different Water Temperatures

The BTUH outputs are listed for 180° water. The following chart may be used to calculate the BTUH outputs for different water temperatures:

Water Temperature Multiply the Listed BTUH output (180°) by:
120° 0.38
130° 0.48
140° 0.57
150° 0.67
160° 0.78
170° 0.89
180° 1
190° 1.13

To size the radiators it is necessary to calculate a house’s heating requirement.  This calculation measured in BTU/Hour should be done on a room-by-room basis either by a heating contractor or qualified plumber. The following are some estimates of Heat Requirements for Sample Cities:

City:  BTUH per sq. foot:
Boston 40
Chicago 40
Denver 40
New York City 40
Philadelphia 35
Portland, OR 25
San Francisco 25
Seattle  25
Toronto 40
Washington, D.C.  35
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