Water Pump Motor Horsepower Calculator

Pump Motor Horsepower Formula:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Flow Rate (Q):

GPM

Total Head (H):

feet

Specific Gravity (SG):

(1 for water)

Pump Efficiency (η):

(0.7-0.9 typical)

Required Motor Horsepower:

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1. What is the Pump Horsepower Equation?

The pump motor horsepower equation calculates the power required to move a fluid through a system based on flow rate, total head, fluid properties, and pump efficiency. It's essential for proper pump selection and system design.

2. How Does the Calculator Work?

The calculator uses the pump horsepower formula:

\[ HP = \frac{Q \times H \times SG}{3960 \times \eta} \]

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total head in feet
\( SG \) — Specific gravity of fluid (1.0 for water)
\( \eta \) — Pump efficiency (decimal, typically 0.7-0.9)
3960 — Conversion factor for units

Explanation: The equation calculates the theoretical power required to move the fluid, then accounts for pump inefficiency to determine actual motor horsepower needed.

3. Importance of Proper Pump Sizing

Details: Correctly sizing a pump motor ensures efficient operation, prevents energy waste, avoids premature motor failure, and ensures adequate flow and pressure for the system requirements.

4. Using the Calculator

Tips: Enter flow rate in GPM, total head in feet, specific gravity (1.0 for water), and pump efficiency (typically 0.7-0.9). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is total head?
A: Total head is the sum of static head (vertical distance), friction head (pipe resistance), and pressure head (system pressure requirements).

Q2: Why is efficiency important?
A: Pump efficiency accounts for energy losses in the system. More efficient pumps require less motor horsepower for the same output.

Q3: What's a typical efficiency value?
A: Centrifugal pumps typically range from 70-90% efficiency (0.7-0.9). Consult manufacturer data for specific pumps.

Q4: Should I round up the motor size?
A: Yes, motors should be sized 10-20% above calculated HP to account for startup loads and provide a safety margin.

Q5: How does viscosity affect horsepower?
A: Higher viscosity fluids require more power. For viscous fluids, specific gravity alone may not be sufficient for accurate calculations.