05.04 How do I determine the pump motor horsepower and voltage?

The required pump horsepower is determined by the requirements for flow rate and pressure (at the pump) by the following equation. Round up to the next standard motor. For non-submersible pumps these would typically be 0.33, 0.50 0.75. 1.00, 1.50, 2.00, 2.50, 3.00, 5.00. For submersible pumps they would be 0.33, 0.75, 1.50, 2.00, 3.00, 5.00.

Pump voltage selection is usually a function of what is readily available in the building. Motors are typically 120 or 208 VAC Single Phase, or 230 or 460 VAC Three Phase. Submersible pumps in the lower HP range are commonly 208 VAC Single Phase, and in higher HP are available either as 208 VAC Single Phase or 480 VAC Three Phase. Many facilities as a rule of thumb will have all motors under 1 HP to be Single Phase and all motors over 1 HP to be Three Phase.