What RPM For 25 GPM - Pentair SuperFlo
When you get a new variable speed pool pump the first thing you want to do is change your filtration schedule and attempt to start saving money on electricity. As a pool owner you will almost immediately encounter a problem when you attempt to do this. While you have complete control over the pump motor RPM and the amount of electricity that the pump is using, this does nothing to tell you if you are actually filtering your water enough or not. Monitoring how many hours you run your filtration pump for is the old school method for determining filtration schedules for pools. If your motor only ran at one speed then this would be a more practical way to measure your filtration schedule, but with variable speed pumps this is no longer a useful way to measure your filtration schedule.
Instead of running your pump only a few hours per day every variable speed pool pump owner should instead run their pump 24 hours per day. The pool will most likely still require at least a few hours per day of operation at higher motor RPM speeds, but the real savings, and benefits of variable speed pumps come from the long periods of time every day that you run the pump at lower RPM values. The amount of power consumed by pool pumps operating at lower RPM's is extremely small such that you could run your pump on a very low RPM for dozens of hours for the same amount of energy that it would take to run for even a single hour at high speed. Yes the pump moves more water at the higher RPM, but not enough to make up for huge energy savings experienced at lower speeds. To see more examples of low speed versus high speed motor operation you can read this article about how much power does a pool pump use?
Pool filtration is a dynamic equation - Every pool system is unique. The size of plumbing pipes, the orientation of their installation, the number of suction and return lines, the distance from the pump to the pool, the elevation of the pump in relation to the water level in the pool, the number and type of peripheral devices installed on the system...even the type, size and current amount of dirt in your filter all will change how much flow volume you have as well as the amount of power that your pump consumes. Even if you have the same pump shown here, the Pentair SuperFlo VS 342001, the flow rate and electrical consumption for your pool will be unique. This is a bench test only and designed to give you a helpful relative bearing for flow rates versus motor RPM.
25 Gallons per minute
1500 Gallons per hour
36,000 Gallons per 24 hours
25 gallons per minute represents a relatively low flow rate, but one that would add up to be a significant amount of flow if left to run life this for many hours per day. Under ideal filtration conditions you should attempt to filter the entire volume of your pool three times every 24 hours. Some pool owners elect to filter their water less than this amount, which works on some pools depending on who you ask, but filtering your water more means using less chemicals to remove contaminants within the water. These contaminants can often be removed by more aggressive filtration which, in my professional opinion, is preferable to using an excess of chemicals to accomplish the same thing.
In this bench test we were able to achieve 25 gallons per minute from a Pentair SuperFlo VS running at 1350 RPM. The plumbing installation for this test was a single 1.5" suction and return line. At 218 Watts, or .218 kilowatts, this would be 5.23 kWh after a 24 hour running cycle. The nationwide average for electricity cost is $0.13 per kWh so 5.23 kWh would cost a total of $0.68 every 24 hours. This is why variable speed pumps save energy and how running your pump around the clock at low RPM speeds is a big advantage to your pocket book. It is worth noting that most pools require a more dynamic filtration schedule than simply letting the pump run at low speed 24 hours per day. To learn more about this you can read this article about variable speed pump schedules.
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