A big part of the green movement in pools is the adoption of variable-frequency drives (VFDs) and variable-speed pumps. What’s the difference between them?
VFDs are control systems added in front of the electrical input of the larger (7.5 hp and up) 3-phase pump motors. These drives protect the motor from a number of electrical issues such as “single phasing,” which is when one of the three incoming power lines to the motor is lost, in which case, without proper protection, the 3-phase motor will burn up in a matter of minutes.
Additionally, and probably the biggest reason to use the VFD, is to control the motor speed. Uncontrolled motors have two speeds: wide open or off. The VFD allows the user to control the speed of the motor to produce a specific flow of water. By reducing the speed, the user is reducing the energy consumed to run the motor. Even a minor reduction can produce significant energy savings. For example a 10 percent reduction in flow can reduce the energy consumed by approximately 30 percent. For a pool pump motor that runs 24/365 this can produce significant energy savings.
Variable-speed pumps (VSPs) are smaller pumps (3/4 to 3 hp) that have a limited drive unit on the back of the motor. This drive allows the user to set the speed to produce the flow needed. Additionally most VSPs can utilize single-phase power to run the 3-phase motor of the VSP. This allows a much broader usage of the technology, as most pool pumps of this size are wired with single-phase power. Some of the same benefits of the VFD can be enjoyed with VSP but on a smaller scale.
