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Why Do I Need A Variable Speed Pool Pump?

Why do I need a variable speed pool pump?
Why do you need a variable speed pool pump? The short answer to this is because regulations for pool pumps are changing and you will be required to use a filtration pump for your swimming pool that meets an efficiency standard that no single speed pumps will be able to meet. Further to this even the more efficient two speed pumps will likely not meet efficiency requirements either. In between the lines you will be required to get a variable speed pool pump as these will be the only pumps that are able to meet this new efficiency standard. There are a few things to consider about this and I encourage you to refrain from taking a stance against variable speed pool pump technology just because it is something that is more or less being forced upon you. I can certainly appreciate the reaction to oppose being forced to buy an expensive piece of new technology, but I implore you to first consider that this is actually a very, very good thing for you.


Actually a variable speed pump and new energy efficiency standards imposed by the Department Of Energy is more than just good for you, the pool owner. It is good for you (in multiple ways) but more importantly this is a move to improve the industry as a whole and this initiative is going to reduce wasted energy on a global scale. If you consider how many millions and millions of inefficient pool pumps are soon to be replaced with a vastly superior variable speed pool pump you can perhaps appreciate more just how much of a difference this is going to make. Still, the idea of thinking globally is all well and good, but variable speed pool pumps cost a lot of money, usually three to five times the cost of a single speed pool pump, and this is certainly going to frustrate a lot of pool owners trying to keep the maintenance budget down.


The good news - The good news about this whole situation is that the people who will get the most mad about being forced into purchasing a new variable speed pump are doing so because they really don't want to spend all that money. The cold, hard reality is that a pool pump can account for up to 50% of all of the electricity used in an average home with a pool. That is a staggeringly high number that no home owner would accept from any other appliance in their home. Even attempts to run the pool pump only part of the day to mitigate these high electrical costs leave so much room for improvement. If you are mad about purchasing a new variable speed pool pump, you should instead be furious that you were forced to run your pool so inefficiently for so long! If you doubt this then please read this article where I break down the electrical costs for running a single speed pool pump four hours daily, versus the same amount of filtration achieved (for far less money) with a variable speed pool pump: Running a pool pump 4 hours per day cost breakdown.





Flow volume is a critical component to consider - Due to the high cost of running single speed pool pumps many pool owners choose to measure their filtration schedule by the number of hours that the pump is running. Sadly this is a very poor measure of how to determine a filtration schedule for a pool and takes into account none of the information that you need to consider if you want to make an informed decision about how you filter your pool water. The two missing components are you need to decide how much turnover is acceptable for your personal standards, and what your actual flow rates are. Commercially maintained pools require either three or four turnovers of the pool volume every 24 hours. This is to ensure that all of the water in the pool gets filtered at least one time every day. As much as I wish all pool owners followed these established standards, most do not. So first you must decide how much you want to filter you water, with most pool owners typically achieving between one to two turnovers of the pool daily. This is short of commercial standards but enough to keep most (residential) pools having clear water. Deciding how much to turnover your water is the first thing you need to know, and the second is how much water your system is actually moving at any given time.


Residential pool systems, by and large, do not have any method to monitor the rate of water flow. You might know system pressure, pump RPM, or feel physical movement of water in front of your returns in the pool, but none of these tell you how much water is actually moving. Without knowing this information you will always be in the dark about how much water you are actually filtering in your pool. With older single speed pumps this was less of an important issue, but now every single pool should have a custom schedule of pump speeds in order to achieve adequate filtration amounts while spending the least possible amount on electricity. For more information you should read this article about swimming pool flow meters.


Variable Speed Pool Pump Advantages


Using less electricity is the name of the game for variable speed pool pumps but this would not be a great option if this resulted in lower quality filtration for pools. Fortunately this is not the case and variable speed pumps are actually capable if increasing the quality of your water filtration while still using substantially less electricity than any form of single speed pump scheduling.


In the attached video you can see for yourself the motor RPM, flow rates and electrical consumption of high speed operation versus lower RPM operation of a pool pump. Flow rates go down as motor RPM goes down, but the rate of electrical consumption drops by much more than the flow rate!


Motor speed: 3450 RPM
Power consumption: 2250 Watts (2.25 kW)
Flow rate: 82 GPM


Motor speed: 1730 RPM
Power consumption: 360 Watts (0.36 kW)
Flow rate: 38 GPM


When you calculate each of these scenarios for Watts / gallon you see that the full speed operation of the pump costs three times as much per gallon as the half speed operation does (9 Watts per gallon versus 27 Watts per gallon). Most importantly this is just the tip of the iceberg (of savings) as most pools can, and should, run the pump for extended periods every day at RPM speeds even lower than this half speed 1730 RPM example. This will further improve your cost per gallon calculation in your favor. There can be no argument, and the numbers are very much black and white, variable speed pumps are vastly more energy efficient than any form of single speed pool pump operation. But that is not where the benefits of a variable speed pump end:


Quieter operation - The full speed operation of your variable speed pool pump will be similar in noise level to older single speed pool pumps. However a properly scheduled VS pool pump should only operate at maximum RPM for a few hours per day at most. This means the rest of the day (and night) will see your pump operating at volumes much lower than full speed operation.


TEFC motors - New variable speed pumps are TEFC (totally enclosed, fan cooled) motors which are substantially less prone to failure from environmental problems than older style single speed pumps which are open to air, and in fact draw ambient air through the motor to help keep it cool. This can and does result in a great deal of pump failures from dust, debris, moisture or proximity to salt water...any of these can kill an open air motor, and all of these problems are avoided with new TEFC pumps.


Improved motor efficiency - Variable speed pool pumps use permanent magnet motors where traditional single speed pool pumps use ACIM (alternating current induction motors) which are less efficient overall than permanent magnet motors. This means even apples to apples, like two pool pumps both operating at full speed, the permanent magnet motor will be more efficient. Efficiency is different for each pump, however most ACIM pumps are in the 80% range for efficiency, while most permanent magnet motors are in the 90% efficient range.


Reduced system losses - Water moves much more efficiently at low speeds than it does at higher speeds. For example, as seen in this video, the maximum speed achieved was 82 GPM with 1.5" pipe when the pump was running at high speed, however the maximum speed for efficient water flow in 1.5" pipe is less than 35 GPM. As water flow exceeds 35 GPM in this pipe, you will begin to experience losses due to friction and turbulence within the system. With variable speed pumps the majority of your filtration day will be within the most efficient flow parameters for your pipe. For single speed pumps the entirety of their operation schedule is well outside of the efficient range of flow.


Why do you need a variable speed pool pump? You need one to meet the new regulations for "Energy Conservation Standards for Dedicated-Purpose Pool Pumps" which come into effect in 2021. Between the lines you need one to get rid of your old pool pump which is essentially as energy efficient as a ruptured oil tanker. Polar bears are almost extinct people, and besides, this act of greater good is actually going to benefit you directly by saving you more in electricity than you pay for your new pump. If you want to see how this can be possible you should read this calculation of savings from a variable speed pump.


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Swimming Pool Steve

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