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Boiler Horsepower

Boiler horsepower vs. heat transfer area.

Boiler horsepower - a power unit from the 19th-20th centuries - was  used to rate the capacity of a boiler to deliver steam to steam engines.

A common definition of one boiler horsepower is the amount of energy required to produce 34.5 pounds (15.65 kg) of steam per hour at pressure and temperature 0 psig (0 bar) and 212oF (100oC) - with feed water at pressure 0 psig and temperature 212oF. One boiler horsepower is about 33479 Btu per hour (about 9812 watts, 8437 kcal/hr).

Boiler horsepower was used in USA, Australia, and New Zealand and have been calculated in different ways. 

PBoHP = A / k                                   (1)


PBoHP = boiler horsepower

A = heat transfer area (ft2)

k = standard area (ft2) - in New Zealand it was common to use 17, in US it was common to use 10 before year 1900 - and more common to use 5 after 

Be aware that the a boiler horsepower is not the commonly accepted 550 ft lbf/s and the generally accepted conversion factor of 746 Watts = 1 horsepower does not apply.

Boiler Conversion Ratios

Boiler Conversion Ratios
from multiply to
sq.ft. EDR steam 240 Btu per hr.
sq.ft. EDR water 160 Btu per hr.
Boiler hp 33.5 MBtu per hr.
Boiler hp 140 sq.ft. EDR steam
Boiler hp  223 sq.ft. EDR water
Boiler hp 34.5 lb. per hr. steam
lb. per hr. steam 970 Btu per hr.
to divide by above from

Related Topics

  • Thermodynamics

    Calculate heat, work, temperature and energy. The thermodynamics of steam and condensate systems. Water and Ice properties.

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