Replacing a Single Speed Pump with a Variable Speed Pump
Since the pool pump is the most significant user of energy in the pool system, replacing a standard single speed pump with a variable speed pump should result in significant energy and energy cost savings.
The installation is similar to that of a single speed pump and only involves a little extra care with calculating and programming the best flow rates for the pool filtration system.
In this article, we look at replacing a single speed pump with a variable speed pump.For maximum efficiency both the minimum required flow rate and the maximum flow rate need to be calculated. To determine these flow rates, the pool should be measured and the volume of water calculated by these measurements.
For a standard rectangular pool the formula for volume is:
Length x Width x Average depth = Cubic Feet of water
Cubic Feet x 7.48 = Pool volume in gallons
For custom pool shapes the calculations are more involved, but there are a number of pool volume calculators available online from a variety of sources. Just search for “Pool Volume Calculator” to find any number of these.
Minimum Flow Rate
Once the pool volume in gallons is known, the minimum required flow rate may be determined. For sanitary and clear water the total volume of the pool should turn over a least once every 24 hours. The minimum flow rate in gallons per minute is obtained by dividing the volume by minutes in a day.
Minimum Flow Rate (GPM) = Pool Volume / 1440 (Total minutes in 24 hours)
Maximum Flow Rate
For the best efficiency, the maximum flow rate should also be calculated. The equation adopted by the Association of Pool and Spa Professionals for maximum flow rate is based on a 6 hour volume turnover.
Maximum Flow Rate (GPM) = Pool Volume / 360 (Total minutes in 6 hours)
There are a wide variety of variable speed pumps and filtration and control systems so we won’t go into great detail on the actual installation of each pump.
Plumbing and electrical considerations are the same as those in a single speed pump. Most variable speed pumps do have both timing and control features built in so the wiring may be somewhat different from the pump being replaced.
Always follow the manufacturer’s instructions and safety guidelines for each pump. Variable speed pumps always include a rather detailed set of installation and operations manuals and the manufacturers are usually quite helpful with any questions that may come up.
With energy savings being the main feature of variable speed pumps, the ultimate goal is provide proper filtration and circulation for the pool at the lowest motor speed.
The pump should be set to provide at least a 24 hour turnover period, and depending on bather load, rain, and debris, a faster turnover rate may be required.
The pool owner should be familiar with the variable speed pump operation and should monitor the water as to see if any adjustments may be needed.
Most variable speed pumps also offer the ability to set up a bypass mode for special situations such as a heavy bather load or storm without having to reprogram the controller.
Special features, such as waterfalls pool cleaners and other water features need to be programmed in at this time and the owner’s, and installation manuals usually provide plenty of guidance in this area.
The basic advantage of a variable speed pump is its flexibility in providing the proper water flow under any condition. This may take a bit of extra care at the start but the savings in energy and cost, along with the ability to tailor the pump flow the pool needs, should provide the pool owner with the best possible pool experience.
Replacing a single-speed pump with a modern variable speed pump is relatively quick and simple. In order to successfully complete the task, the installer must calculate the number of gallons of water in the pool and calibrate the new pump to circulate water at an appropriate rate.
Interested in switching or learning more? Stop by one of our three locations and let our expert staff help you make the change!