1. What is Fan Horsepower?

Fan horsepower (HP) is the power required to move a specific air flow rate against a given pressure difference at a certain efficiency. It's a crucial parameter in HVAC system design and fan selection.

2. How Does the Calculator Work?

The calculator uses the fan horsepower equation:

Where:

• \( Q \) — Air flow rate (cfm)
• \( \Delta P \) — Pressure difference (in wg)
• \( \eta \) — Fan efficiency (0-1)
• 6356 — Conversion factor (cfm·in wg to hp)

Explanation: The equation calculates the theoretical power needed to move air, accounting for flow rate, pressure resistance, and system efficiency.

3. Importance of Fan HP Calculation

Details: Accurate fan horsepower calculation is essential for proper motor sizing, energy efficiency assessment, and system performance evaluation in ventilation and air movement applications.

4. Using the Calculator

Tips: Enter air flow in cfm, pressure difference in inches water gauge, and efficiency as a decimal between 0 and 1. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical fan efficiency range?
A: Typical fan efficiencies range from 0.4 to 0.75 (40-75%), with higher efficiency in well-designed centrifugal fans.

Q2: How does pressure difference affect HP?
A: HP increases linearly with pressure difference - doubling ΔP doubles the required HP at constant flow.

Q3: What are common cfm ranges for fans?
A: Small fans might move 100-500 cfm, while large industrial fans can move 50,000+ cfm.

Q4: Why is the conversion factor 6356?
A: This factor converts (cfm × in wg) to horsepower, accounting for units and standard air density.

Q5: Should I add a safety factor to the calculated HP?
A: Yes, it's common practice to add 10-20% safety factor when selecting motor size to account for system variations.