Boiler Horsepower

Boiler horsepower - a power unit from the 19^th-20^th 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 211 ^oF (100 ^oC) - with feed water at pressure 0 psig and temperature 211 ^oF. 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. 

P_BoHP = A / k                                   (1)

where

P_BoHP = boiler horsepower

A = heat transfer area (ft²)

k = standard area (ft²) - in New Zealand it was common to use 17, in U.S. 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