manuals

IC Pump Station Instruction Manuals

Technical:

1. Calculating Pump Horsepower. Pump Horsepower needed to pump a given rate of flow (gallons per minute) at a given pressure (PSI) is determined by the formula: (GPM X PSI)/3960. This figure must be divided by the pump efficiency (expressed as a decimal). Pump efficiency information is obtained from the pump curve information published by the pump manufacturer.

Below is a typical pump curve for pumps from 5-40 HP. The vertical (y) axis is feet of head (one foot of head = 0.433 PSI) and the horizontal (x) axis is PSI. The higher the flow rate the lower the PSI and vice versa for a given horsepower. The pump efficiency depends on the rate of flow (note the efficency curve at the right of the graph. Typically pumps are selected based on the flow rate needed for the best efficiency. Higher efficiency means you pay less for power to pump a given rate of flow at a given pressure.

2. Calculating Pump Power usage.

Single Phase power: Power (in watts) = Volts X Amps X Power Factor*.

Three Phase power: Power (in watts) = Volt X Amps X Power Factor* X 1.73

*Power factor is phase shift that results in increased power using the alternating current waveform. One essential gets extra power "for free" using the AC waveform. Power factor changes with motor RPM and lower motor loads (HP) net "better" power factor figures. Below is a motor curve for a 25 HP 240 or 480 volt three phase pump motor.