Centrifugal Pump Motor Selection based on Operating Costs

Which electric motor should be selected to drive a centrifugal pump based on operating costs?

If electricity costs $0.07 per kilowatt-hour and MARR is 8% per year, which motor should be selected?

Answer:

To determine which motor should be selected for the centrifugal pump, we need to compare the operating costs of each motor. Motor 2 should be selected as it has lower operating costs than Motor 1.

Explanation: To determine which motor should be selected, we need to compare the operating costs of each motor. The operating cost can be calculated by multiplying the power consumption of the motor (in kilowatts) by the cost of electricity per kilowatt-hour and the number of hours the motor will be in use. Let's calculate the operating costs for each motor:

Motor 1: Power consumption = 60 horsepower * 0.746 kW/hp = 44.76 kW. Operating cost = 44.76 kW * $0.07/kW.h * 800 hours = $2504.64.

Motor 2: Power consumption = 60 horsepower * 0.8 * 0.746 kW/hp = 28.368 kW. Operating cost = 28.368 kW * $0.07/kW.h * 800 hours = $1591.94.

Based on the operating costs, Motor 2 should be selected as it has lower operating costs than Motor 1.