What is the final calculated horsepower value given in the example?

• A. 3.2 HP
• B. 4.0 HP
• C. 5.1 HP
• D. 6.8 HP

Answer: (C)

The core idea is turning the boiler’s useful energy output into horsepower by using the standard BTU per hour to horsepower conversion. You first compute the useful energy rate the boiler delivers (in BTU/hr) from the mass flow and the enthalpy change, adjusting for efficiency. Then you convert that rate to horsepower with HP = (useful BTU/hr) ÷ 2544.43. In the example, the useful output comes to about 12,960 BTU/hr. Dividing by 2544.43 yields roughly 5.11 HP, which rounds to 5.1 HP. That’s why the final value is 5.1. The other options would require a different useful energy rate or a different rounding, so they don’t match this calculation.