Pump Motor Horsepower Calculator

Pump Motor Horsepower Formula:

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

Flow Rate (Q):

GPM

Head (H):

Specific Gravity (SG):

Efficiency (η):

decimal (0-1)

Motor Horsepower (HP):

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1. What is Pump Motor Horsepower?

Pump motor horsepower is the power required to move a fluid at a specified flow rate against a specified 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:

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

Where:

\( Q \) — Flow rate in gallons per minute (GPM)
\( H \) — Total head in feet (ft)
\( SG \) — Specific gravity of the fluid (dimensionless)
\( \eta \) — Pump efficiency (decimal from 0 to 1)
3960 — Conversion factor (foot-pounds per minute per horsepower)

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

3. Importance of Horsepower Calculation

Details: Proper horsepower calculation ensures the pump motor is correctly sized - neither undersized (which would fail to meet requirements) nor oversized (which would waste energy and increase costs).

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is specific gravity?
A: Specific gravity is the ratio of the fluid's density to water's density at standard conditions. Water has SG=1.0.

Q2: How do I estimate pump efficiency?
A: Centrifugal pumps typically have 70-90% efficiency. Check manufacturer data for specific pumps.

Q3: What's the difference between brake horsepower and motor horsepower?
A: Brake horsepower (BHP) is power delivered to the pump shaft. Motor horsepower includes additional power to overcome motor inefficiencies.

Q4: Should I add a safety factor?
A: Yes, typically add 10-20% to the calculated horsepower for safety margin and future needs.

Q5: How does viscosity affect horsepower?
A: High viscosity fluids require more horsepower. The calculator works best for low-viscosity fluids like water.