Problem Solver - August 2014
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Improve Pump Room Efficiency

Many aquatic facilities looking to lower their operational costs find that energy usage is a good place to start. Greening the pump room helps lower the utility bills associated with running a swimming pool.

Q: What can we do to make our facility more efficient and reduce operating costs?

A: Proper pump selection and optimal flow rates can help increase energy savings. Affinity laws indicate the power demanded by a pump is proportional to the cube of the flow rate. For example, if the pump's flow rate is doubled, its power demand is increased by a factor of eight. Therefore, it is important to utilize the smallest pump capable of completely turning over the pool's water in an acceptable amount of time.

The type of filter used (cartridge, sand or diatomaceous earth) can have a significant impact on energy consumption, as each type places different levels of resistance on the circulation system. Of the three types, cartridge filtration offers the least resistance to flow. Both sand and D.E. filters require multi-port valves to perform routine backwash procedures, creating more resistance. Newer backwash valves have been designed to lessen flow resistance. Using a filter that does not require backwashing helps conserve both water and chemicals.

A dirty filter also can increase the pump's workload. Simply keeping the filter clean and the skimmer basket free of leaves and debris can deliver energy savings.

Q: How can a variable speed pump help?

A: Historically, pool pumps with induction motors, which operate at one or two speeds, have drawn more energy than is required to circulate pool water. Some variable speed pumps (VSPs) have built-in, constant-flow software, which maximizes the advantages these pumps have to offer, as it will automatically adjust speed to deliver the required flow rate for each programmed task. No matter what type of pump is being used, slower pump speeds save energy.

Q: What should we know about variable frequency drives?

A: To ensure the swimming pool operates efficiently, the first place to start is with a properly designed circulation system. Each component in the system (piping, fittings, valves, filters, heaters, etc.) produces a pressure drop (friction loss), which the pump must overcome. The total pressure drop in the system is commonly referred to as total dynamic head (TDH). The larger the TDH, the greater the amount of power required to achieve a given flow rate.

For larger horsepower pumps, variable frequency drives offer a significant return on investment. 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.

Just by installing a VFD, you can save as much as 5 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. Variable frequency drives: "right-size" your pump to the exact flow required; save energy with constant flow as the filter gets dirty (with optional flow sensor); offer "off-hour" flow management capability; provide high-efficiency, up to 98 percent; eliminate the need for motor starters; have two-step ramps (soft start feature); provide overload trip protection to protect the motor and drive from voltage spikes and phase unbalance; and save up to 60 percent or more on pump's electricity usage.

With the substantial energy-use rebates that some local power companies offer, in conjunction with the savings in daily operational expenses, some end-users are getting back approximately 50 percent of the pump's cost in less than a year when they add a variable frequency drive and upgrade their pumps.


Pentair Commercial Aquatics

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