Variable Speed Pool Pump Mistakes
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By now anyone (everyone) with a swimming pool should be familiar with variable speed pumps or at least have heard of them to the extent that they understand VS pumps are now required for filtration pumps on all swimming pools. Or at least you can say that filtration pumps are now required to meet efficiency standards of which very few single speed pumps are able to meet. So perhaps you are thinking about getting a variable speed pump for your pool, or even better, you already have one now. The only problem or potential problem is that everyone spends all of their time talking about how great variable speed pumps are and how much they will save you on electricity...but nobody really explains how to make that happen.
Let me give you an example in that the Department of Energy requires that you now have this super efficient pool pump (mostly variable speed models) but there is absolutely no mention of a flow meter which would be required equipment for the average pool owner to, you know, implement some of that technology that they were essentially forced into buying. In addition to this, supposing you were a reader of this website and already knew the importance of a flow meter for your pool and have one installed along with your new pump, where are the supporting documents explaining how you are supposed to actually use these new pumps. There are a ton of pool owners who are investing in expensive variable speed pumps and then simply running them on full speed for eight or ten hours per day just like they did with their old single speed pump. That means these pool owners are giving up on most of the potential for cleaner water and reduced electrical costs and experiencing only a slight increase in motor efficiency with a new TEFC motor versus the older open motor design which is slightly less efficient.
Run variable speed pumps 24 hours per day - The first thing you need to do when you get a variable speed pump is to understand that running it 24 hours per day is the best way to clean your water, and actually enables you to experience the lowest possible electrical costs filtering your pool. This is a little counter intuitive on the surface which leads many pool owners to running their pump for only part of the day. This is how you used to save money with a single speed pump however turning off a variable speed pump does nothing more than limit the potential for electrical savings you can experience. In short, if you are able to run your pump only part of the day and still have clear water, then you simply need to filter the exact same volume of water but spaced over a 24 hour period and this will drastically reduce your operation costs.
Whatever speeds you operate now that keep the pool clean in a partial day can be reduced in order to filter the same amount of water after 24 hours that you do now on a reduced schedule. Your pool only needs a few hours per day at higher speeds and about double that for medium speeds. They remainder of the day, which is the by far the bulk of the day, should be running at low RPM values to achieve reasonable GPM flow rates that add up to huge volumes of filtered water by the end of the day. The more low speed operation you have with your pump the better as the filtration quality is typically high at lower speeds and the cost per gallon of filtration is lowest when the pump is at low speeds...by a large margin actually. There is something to be said for unique flow rates being needed for every pool however there are many misconceptions, like salt systems need to run for long periods of time so you have to run your pump at higher speeds. When I tested this I was surprised to find out how little RPM you actually need to close the flow switch on a pool salt system, or even a gas pool heater!
Run your variable speed pump below maximum speed - The math behind power consumption for an electric motor is interesting in that at maximum motor RPM, 3450, the power consumed is extremely high. If you reduce the motor RPM by even a small amount you should notice a pretty drastic difference in the amount of power that is being consumed. More interestingly is that flow rates follow a linear drop as you reduce motor RPM however power consumption does not. Power consumption goes down 8x for a drop in RPM by half. The takeaway here is that if you run your pump at maximum RPM for any period of time daily you are probably leaving a good chunk of potential electrical savings on the table. By reducing the maximum RPM that you run your pump at you can reduce on your total electrical consumption by a significant percentage.
If you for example ran your pump at maximum speed for four hours per day as part of your regular filtration program then you might want to explore reducing the RPM from 3450 to 3200 or even 3000. You might not notice much if anything in terms of reduced flow and filtration but the cost to run the pump for those hours will go down by a lot. When you are designing a variable speed pump filtration schedule you are really trying to take every opportunity to reduce power being consumed. Buying and installing the pump is only the very first step in the process! Very few pools will need to run a pump at 3450 RPM and be unable to reduce to at least 3200 without experiencing problems. If your pump runs at 3450 RPM for any period of time during the day there is a good chance you are leaving money on the table. Plus higher RPM generates more heat which is undoubtedly one of the main causes of electric motor failure. It only stands to reason that a pump that runs cooler will outlast a pump that runs hotter.
Installing a variable speed pump that is too large - This has always been a problem within the pool and spa industry as pool owners tend to think that more horsepower must be better and manufacturers tend to exploit this by advertising inflated horsepower ratings using a tricky little move called service factor where a pump can be essentially over rated. If you are familiar with stereo and speaker applications this is similar to buying a 1000W speaker which is actually only a 700 Watt RMS speaker (root, means, square) with a peak potential wattage of 1000W. Just like a 2 HP pump which is actually a 1.5 HP or smaller with a peak rating of 2.0 HP for short bursts. This is a confusing subject that is fortunately a disappearing problem now that WEF ratings are being implemented which will level the playing field of comparing the efficiency of one pump to the next. When it comes to variable speed pumps what you need to realize is that almost all of the pumps on the market are giant. Seldom do you need a pump anywhere near to two or three horsepower for a filtration pump...not even if your pool is a gigantic 40,000 gallon monster. A 1.5 horsepower pump, or even less, still has more than enough power for filtering water effectively and efficiently. By oversizing you pump purchase you serve only to increase the cost to run the pump minute by minute, but you are (seriously) risk overdriving your pool filter. Sand filters are notorious for having low maximum designed flow rates. Modern variable speed pumps, especially those in the 2 and 3 horsepower range, are far too powerful to be used with most sand filters. Variable speed pumps are better paired with cartridge filters or DE filters, both of which typically boast much high maximum designed flow rates.
When you decide to invest in a variable speed pump you have made a sound technical decision which is very likely to reward you with cleaner, clearer water (which uses less chlorine) combined with lower electricity costs to operate your swimming pool. Be sure to get the most out of this investment by following these three tips. If you want more information about how to program variable speed pumps to maximum benefit you might want to read this article on variable speed pump programming. You can also check out this article that shows a variable speed pump 24 hour filtration schedule that costs less and pumps more water than a single speed pump that only runs 8 hours per day.
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Swimming Pool Steve is an award winning, second generation swimming pool and spa specialist from Ontario Canada. With over 10,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the 2018 Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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