1. What is Pump Motor Horsepower?

Pump motor horsepower is the power required to move a fluid at a specified flow rate against a given head, accounting for the fluid's specific gravity and the pump's efficiency. It's a crucial parameter in pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

Where:

• \( Q \) — Flow rate in gallons per minute (GPM)
• \( H \) — Total head in feet (ft)
• \( SG \) — Specific gravity of the fluid (1 for water)
• \( \eta \) — Pump efficiency (decimal between 0 and 1)
• 3960 — Conversion factor (ft·lb/min per HP)

Explanation: The equation calculates the theoretical power required to move the fluid, then divides by the pump's efficiency to get the actual motor power needed.

3. Importance of Horsepower Calculation

Details: Proper horsepower calculation ensures the pump motor is correctly sized - too small will be overloaded, while too large is inefficient and costly.

4. Using the Calculator

Tips: Enter flow rate in GPM, head in feet, specific gravity (1 for water), and pump efficiency as a decimal (e.g., 0.85 for 85%). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical pump efficiency value?
A: Centrifugal pumps typically range from 50-85% efficiency, with higher efficiency in larger, well-designed pumps.

Q2: How does specific gravity affect horsepower?
A: Higher specific gravity fluids (denser than water) require more power to pump at the same flow rate and head.

Q3: What if my pump has variable speed?
A: This calculation gives the power at the specified operating point. Variable speed affects flow and head, changing power requirements.

Q4: Should I add a safety factor?
A: It's common practice to add 10-20% to the calculated HP to account for system variations and future needs.

Q5: How does viscosity affect the calculation?
A: High viscosity fluids may require special corrections as they affect both pump performance and efficiency.