Guest Column - September 2015
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Performance Improvement

Save Energy Costs, Extend Motor Life With Variable Frequency Drives

By Mike Fowler

Over the past few years, waterpark facility managers have learned that going "green" can significantly lower an aquatic facility's operating costs. Pumps and filters are among the items most scrutinized due to the vast amount of energy they consume. To reduce costs associated with water circulation and filtration, it is important to understand why pumps and filters consume large amounts of energy and what options are available to lower consumption—factors that also extend the motor life of the pump. This article will provide a few easy-to-follow steps to help facility managers determine the best way to extend the life of their pump motors and reduce operational costs using variable frequency drives.

Variable Frequency Drives

Variable frequency drives offer a significant return on investment for waterpark facility managers. These drives allow the pump to run at its most efficient point on the curve, and preventative maintenance costs drop due to motor protection, motor soft start and a significant decrease in water hammer protecting the shaft and impeller.

The VFD does several things, but among the key features is that it will clean up the power going to the pump it's attached to, thus giving good solid power and voltage to the motor and helping to lengthen the life of that motor. It will also allow for better control of the pump itself and allow the drive to dial in the pump to exactly the flow rate that is needed rather than using butterfly valves to bring the pump to within the given parameter. The VFD would also house the motor starter, which without the use of the VFD would have to be purchased separately at a cost of $500 to $750. One last key thing that a VFD can do is allow for a ramp-up start of the motor, which makes life easier on the motor and will also eliminate the potential water hammering effect on the plumbing systems.

Why Add a VFD to a Waterpark Pump Room?

Just by installing a VFD to your pump, you can save as much as 5 percent to 10 percent in energy costs by simply dialing in the pump where it actually needs to be and cleaning the power being sent to the motor. What waterpark wouldn't want to put 5 to 10 percent savings for each pump back into their budget?

Variable frequency drives do the following:

  • "Right-size" your pump to the exact flow required.
  • Save energy with constant flow as the filters get dirty (with optional flow sensor).
  • Offer "off-hour" flow management capability.
  • Provide high efficiency—up to 98 percent. Adjust drive input voltage for best efficiency point.
  • Eliminate need for motor starters.
  • Two-step ramps (soft start feature).
  • Overload trip protection protects motor and drive from voltage spikes and phase unbalance.
  • Save up to 60 percent or more on pump's electricity usage.

In order to quantitatively work on reducing the operating costs associated with running your facility's pump room, you must start by determining exactly what it costs to run your system. In order to determine this figure, you must first determine the GPM and TDH of the pump, how long each day the pump runs and what cost per kilowatt hour your power company is charging. Once you have a clear dollar figure to tackle, you will be able to easily determine the payback of adding a variable frequency drive.