# What size electric motor should be used to drive a fan with 40% static efficiency?

What factors need to be considered in determining the size of the electric motor required to drive a fan with 40% static efficiency?

The size of the electric motor needed to drive a fan with 40% static efficiency depends on factors such as the fan's capacity, static pressure, and static efficiency. In this case, the fan has a capacity of 60,000 ft3/hr at 60°F and a barometer of 30 in Hg, with a static pressure of 2 in WG on full delivery. To calculate the power required for the electric motor, we need to consider these parameters and apply the relevant formula.

## Calculating the Power Required

**Power (HP) = (Flow Rate * Static Pressure) / (Fan Efficiency * 6356)**Converting the given capacity of 60,000 ft3/hr to cubic feet per minute (CFM), we get:

**Flow Rate (CFM) = 60,000 ft3/hr / 60 min/hr = 1000 ft3/min**Substituting the given values into the formula, we have:

**Power (HP) = (1000 * 2) / (0.4 * 6356) ≈ 0.793 HP**Rounding off to the nearest option, the size of the electric motor required to drive this fan is 0.8 HP. Therefore, the correct answer is: O 0.8 HP.