**Output Power**

BHP = Q x SP / (6356 x Fan Ef f.)

Where

• BHP = Break Horsepower

• Pt = Total pressure, in-WG

• Q = Air flow rate in CFM

• SP = Static pressure in-WG

• FAN EFF = Fan efficiency usually in 65–85% range

**Fan Motor Horsepower**

Motor HP = BHP / MotorEFF

Where

• BHP = Break Horsepower

• MotorEFF = Motor drive efficienc y usually 80-95%

**Tip Speed**

Ts = 3.14 x D x N

Where

• Ts = Fan tip speed, FPM

• D = Fan diameter, ft

• N = Fan speed, RPM

**V-belt Length Formula**

Once a sheave combination is selected we can calculate approximate belt length. Calculate the approximate V-belt length using the following formula:

L = 2C + 1.57 * (D+d) + (D-d)2/ 4C

Where

• L = Pitch Length of Belt

• C = Center Distance of Sheaves

• D = Pitch Diameter of Large Sheave

• d = Pitch Diameter of Small Sheave