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)
where
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
| 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 |