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Thread: I would at least look into multi-speed pumps

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    BoDarville's Avatar
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    I would at least look into multi-speed pumps

    Split off of this topic. JasonLion

    dennard:

    Dittos to what scooperhsd stated, especially since both pumps you are looking at are 2-speed.

    As long as you are in the market for a pump, I would at least look into multi-speed pumps and do some cost/benefit/payback analysis for your pool using local electric rates. The energy savings can be significant. I currently have a single-speed. When it comes time to replace it, I will only be looking at 2-speed and multi-speed pumps.

    I hesitate to post hard numbers mainly because there are variations from pool to pool including optional water features and also because someone will usually dispute specific numbers which may lead to confusion. However, since I can cite references, I will make an exception in this case. When you reduce a pool pump's speed to half (50%) of full speed, the kilowatts needed to run it are approximately 1/8 of what it takes compared to running it at full speed. To achieve the same water turnover rate, you need to run the pump for twice the amount of time at half-speed compared to full speed. Accounting for that increased run time at half-speed, your still only using 1/4 the kilowatts to get one turnover of water compared to running the pump at full speed.

    With that said, the above numbers are obtained in controlled laboratory conditions where all other factors are held constant. As stated above, each pool (and its features) is different and "your mileage may vary." Based on my example above (running at 1/2 speed for twice as long), the actual energy used will be between 1/4 and 1/2 of the kilowatts under real-world conditions - still a significant savings either way.

    Multi-speed pumps can offer even more speed flexibility and energy savings compared to 2-speed pumps, but you also need to consider the initial cost differential and factor that into your cost-benefit/payback analysis based on your electric rates.

    Here are a couple of articles that explain the energy use factors in more detail:
    http://www.swimming-pool-information.co ... pumps.html
    http://www.articlecity.com/articles/hom ... 5162.shtml
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    mas985's Avatar
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    Re: need help decideing which pump

    Quote Originally Posted by BoDarville
    When you reduce a pool pump's speed to half (50%) of full speed, the kilowatts needed to run it are approximately 1/8 of what it takes compared to running it at full speed. To achieve the same water turnover rate, you need to run the pump for twice the amount of time at half-speed compared to full speed. Accounting for that increased run time at half-speed, your still only using 1/4 the kilowatts to get one turnover of water compared to running the pump at full speed
    Not quite true. Those references are not using the affinity laws properly because the affinity laws do not include efficiency and that must also be taken into account. The BHP (impeller shaft power) reduction is approximately 1/8th but two speed motors lose about 1/2 their efficiency on low speed so in reality, the energy use goes down by only 1/4 on low speed. Therefore, the net reduction in energy use including the increase in run time is about 50%. Still pretty good.

    Also, the 1 1/2 HP Dynamo is SPL rated which is like a double up rating so it is identical to the 1 up rated HP Dynamo and would have similar performance as a 3/4 HP full rated pump if they made one. So in fact, that pump is really quite small and sized appropriately to that filter.
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    BoDarville's Avatar
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    Re: need help decideing which pump

    Quote Originally Posted by mas
    Quote Originally Posted by BoDarville
    When you reduce a pool pump's speed to half (50%) of full speed, the kilowatts needed to run it are approximately 1/8 of what it takes compared to running it at full speed. To achieve the same water turnover rate, you need to run the pump for twice the amount of time at half-speed compared to full speed. Accounting for that increased run time at half-speed, your still only using 1/4 the kilowatts to get one turnover of water compared to running the pump at full speed...With that said, the above numbers are obtained in controlled laboratory conditions where all other factors are held constant. As stated above, each pool (and its features) is different and "your mileage may vary." Based on my example above (running at 1/2 speed for twice as long), the actual energy used will be between 1/4 and 1/2 of the kilowatts under real-world conditions - still a significant savings either way.
    Therefore, the net reduction in energy use including the increase in run time is about 50%. Still pretty good.
    I think we are essentially saying the same thing - at the end of the day figure on about a 50% or so reduction in energy use.

    The OP (dennard) had asked "...need some help picking one of these two pumps or maybe a different one if someone has a suggestion." The point of my post was to offer the OP a suggestion to research multi-speed pumps to see if that made sense in his/her situation regarding cost-benefit / payback vs. local electric rates. Wanted to give some guidance on potential energy savings based on the references I had (which essentially said the same thing). Don't want to get off topic by getting into the minutiae of trying to pinpoint the exact energy reduction (too many variables in play to do that) but rather give an expected range. So, I'm going to let that part of the discussion rest.

    Sticking to OP's main topic, here is another article from Pentair who manufactures a complete line of pumps. The summary is that Permanent Magnet Motors are more efficient than induction motors and that variable-speed pumps offer many more speed options than 2-speed pumps which could lead to even more dramatic energy savings. Not going to quote specific numbers from this article this time...will let it speak for itself.

    http://www.pentairpool.com/pdfs/truth2pumpsB.pdf

    Dennard, I hope this helps in researching your pump purchase. Wouldn't want to see you spend good $ and then later say "Gee, I wish I would have known about that one...would have got it instead." It is a big investment and one that you will have for many years. Would opine that it is worth the time to research so that you will have all the information you need that will guide you to getting the right pump for your specific situation.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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    JasonLion's Avatar
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    Re: I would at least look into multi-speed pumps

    This whole conversation is way too complex for the OP and has nothing directly to do with their question so I have moved it into it's own topic.

    It appears that the OP has an above ground pool. If I am right about that, the Pentair variable speed in-ground pump is totally inappropriate for their situation.
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    BoDarville's Avatar
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    Re: I would at least look into multi-speed pumps

    The Pentair link was intended to provide information about variable speed pumps in general. My post was not intended to recommend that (or any other) specific model.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
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    JasonLion's Avatar
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    Re: I would at least look into multi-speed pumps

    The only available variable speed pumps are all high head pumps. Above ground pools are low head situations, not suitable for a high head pump. If this is indeed about an above ground pool, looking into variable speed pumps is both a waste of time and a distraction from the things that are actually important.
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