1. What is a Pump Motor Sizing Calculator?

Definition: This calculator determines the required horsepower for a pump motor based on flow rate, total head, fluid density, and pump efficiency.

Purpose: It helps engineers and technicians properly size pump motors for various fluid transfer applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( HP \) — Horsepower required
• \( Q \) — Flow rate (gallons per minute, GPM)
• \( H \) — Total head (feet)
• \( \rho \) — Fluid density (pounds per gallon, lb/gal)
• \( \eta \) — Pump efficiency factor (0-1)

Explanation: The formula calculates the theoretical power required to move the fluid, then divides by efficiency to account for real-world losses.

3. Importance of Proper Pump Sizing

Details: Correct motor sizing ensures efficient operation, prevents underpowered performance, and avoids energy waste from oversized motors.

4. Using the Calculator

Tips: Enter flow rate in GPM, total head in feet, fluid density (default 8.34 lb/gal for water), and efficiency (default 0.85). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is total head?
A: Total head is the total equivalent height that the pump needs to overcome, including static head, friction losses, and pressure differences.

Q2: What's a typical pump efficiency?
A: Most pumps operate between 70-90% efficiency (0.7-0.9). Centrifugal pumps typically range 0.6-0.85.

Q3: When would I change the density value?
A: Adjust for fluids other than water. For example, gasoline is about 6.0 lb/gal, while brine can be 8.5-10 lb/gal.

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

Q5: What about motor service factor?
A: Standard motors have a 1.15 service factor, meaning they can handle 15% overload for short periods.