Pumps: Strategies for Savings

Part 1: Energy Audit Can Determine Pump-System Performance

Part 2: Managers Can Install Pumps in a Series or Parallel

Part 3: What are the Typical Pumping System Control Methods?

Part 4: Nameplate Motor Power Information Helps Determine Pumping Power

What are the Typical Pumping System Control Methods?

By Paul McCown - August 2009

Understanding the pumping system’s control method is essential to enhance efficiency, especially with dynamic systems or those that do not operate at steady-state conditions. Typical control methods include:

• Always on, in which the pump motor never turns off

• Time clock, in which a computer turns the pump on and off at predetermined times

• Pressure or flow sensor feedback, in which a computer monitors a pressure sensor or flow sensor and compares the sensor value with the desired computer value, adjusting pump speed for the desired condition. A variable-frequency drive (VFD) controls the pump motor using its own internal control to provide the desired speed.

Control can fall to an operator, who uses a manual switch to turn the pump on and off.

While some systems with multiple pumps only use one pump during operation, other systems alternate among several pumps. This pump-control scheme alternates pump operation to balance the total run-time on the equipment. The goal of this strategy is to minimize maintenance.