Known value
divide by 10
* Steam-coil generators
divide by 5
divide by 67,000
(max kW)
divide by 10
Boiler horsepower
as calculated for licensure requirements
0 HP
Rating horsepower
For licensing, boiler horsepower is determined as follows:
- 10 sq ft of heating surface = one HP
remove one zero from surface (150 sq ft HS = 15 HP) - For steam coil generators: 5 sq ft of heating surface = one HP
remove one zero from surface then double it (150 sq ft HS = 30 HP) - If heating surface is not available, use BTU input
divide BTU input by 67,000 (2,000,000 BTUi ~ 30 HP) - For electrically heated boilers: 10 kW = one HP
remove one zero from kilowatt (500 kW = 50 HP)
* ground wire for the boiler must = feed wire size