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Background <br />What is a Variable Frequency Drive (VFD)? <br />A Variable Frequency Drive (VFD) is an electrical device, normally wall -mounted, designed to <br />monitor and protect a swimming pool/spa filtration or water feature pump. They also vary the <br />frequency or speed of the motor in order to provide a specific <br />flow rate and are installed on the electrical line between the <br />electrical breaker panel, and the pool pump. <br />How does a VFD work? <br />VFDs vary the speed of a pool pump to match the pressure <br />or flow requirements and achieve energy savings. Since pool <br />pump systems run continuously and are typically oversized, <br />energy consumption is high. These systems are oversized to <br />help ensure proper filtration and chemical treatment as well <br />as compensate for clogged filters and maximum pool <br />occupancy. By adding a VFD, the motor speed of the pool <br />pump can be decreased while running the filtration system's <br />valves wide open to allow for maximum flow. When <br />regulating flow, putting a VFD on a time clock enhances <br />efficiency. For example, a pool running around the clock at <br />100 percent can now run at 90 percent during operational <br />hours and 60 percent during non -operational hours.' This <br />reduces energy consumption and costs. <br />5 <br />1. <br />1 <br />VFD Control panel at Kawamoto <br />Swim Stadium, Hilo, HI <br />Photo courtesy of the Department <br />of Parks & Recreation <br />As shown in Illustration 1, the VFD works by converting incoming AC power to DC power, <br />smoothing or conditioning it and delivering modified power to the motor. By varying the <br />frequency of this power, the motor speed is reduced, thus reducing both the flow rate and the <br />amount of energy consumed. The addition of a VFD to a pool pumping system can offer <br />dramatic potential energy savings, while protecting the motor at the same time. This is done <br />completely automatically and without operator involvement, allowing continuous speed and flow <br />control. The ability to adjust motor speed enables closer matching of motor output to load and <br />often results in very large energy savings. <br />1 VFDs and Pool Pumps (EMA Drives and Automation) http://www.emainc.net/newsletter/vfd-s-and- <br />up mps/ <br />Variable Frequency Drives at County Pools: Background 12 <br />