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How to Determine the Amount of Steam Required for Heating Water

To determine the amount or steam required to heat a specified quantity of water using steam at atmospheric pressure (212° F) either in a heat exchanger* or by direct injection.


                                     (Gallons of water) x (Pounds per gallon) x

                                     (Temperature rise in ° F.) = Pounds of steam

                                     (Latent Heat of steam / Btu’s)


Example:  To determine the amount of steam required to heat, 300 gallons of water form 60° to 160° F. in one hour with steam at atmospheric pressure—gallons of water = 300 x pounds per gallon (8.3 lbs.) x temperature rise (100° F.) ÷ latent heat of steam (970 Btu’s)


                                      300 x 8.3 x 100 = 257 pound of steam per hour



Divide 257 by 34.5 (one boiler horsepower = 34.5 pounds of steam production per hour) or approximately 7.5 BHP.


                                           Higher temperature latent heat factors


                        0.0 PSI Gauge = 970.3 Btu’s             25.3 Lbs. Gauge = 933.7 Btu’s

                        5.3 PSI Gauge = 960.1 Btu’s             50.3 Lbs. Gauge = 911.6 Btu’s

                       10.3 PSI Gauge = 952.1 Btu’s            75.0 Lbs. Gauge = 940.5 Btu’s

                       15.3 PSI Gauge = 945.3 Btu’s           100.0 Lbs. Gauge = 888.8 Btu’s


Or – Divide the product of (gallons of water) x (pounds per gallons) x (temperature rise in ° F.) by 33,479 number of Btu’s in one boiler horse power to obtain boiler horse power = 7.5 from the example above.


Both of the above methods assume 100% efficiency.  Add 25% to compensate for radiation heat loss, which is certain to occur.  This will determine the minimum boiler horsepower required.


Note: One Btu will raise the temperature of one pound of water one ° F.


*Assumes sufficient heat exchange surface.

Steam Table
Utility Series Steam Boiler
Automatic Balance Control Series Steam Boiler
Pounds of water evaporaed to one boiler horsepower table
Contact us to discuss the requirements of your specific application.  With 75 years in the business, ESG Speedylectric knows steam boilers. 
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