Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 13 of 13

Thread: The most energy efficient two speed pump

  1. Back To Top    #1
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    The most energy efficient two speed pump

    I am a little confused about what the most energy efficient two speed pump is. According to the California pump efficiency test results the Pentair WhisperFlo WFDS-3 on low speed is the most energy efficient pump they tested that isn't a variable speed.

    But then I saw this:
    Quote Originally Posted by mas985
    Here are a few 3/4 HP Full rated and 1 HP Up rated, same size, pumps to consider. They are in order of efficiency from high to lower and THP lower to higher, yes there is a reason for that.

    Hayward SuperPump 1 HP Uprated SP2607X102S
    Pentair SuperFlo 3/4 HP Full Rated SF-N2-3/4A
    Sta-Rite SuperMax 3/4 HP Full Rated PHK2RAY6D-101L
    Pentair Whisperflo 3/4 HP Full Rated WFDS-3
    Pentair Whisperflo 1 HP Up Rated WFDS-24
    The Hayward SuperPump SP2607X102S only appears in the CA data at a single speed, and they don't specify which speed that is. If we assume that they tested it at high speed, then it is just a hair better than the WFDS-3 at high speed, and so we might assume that it is also better at low speed, though that information is not in fact listed.

    The Pentair SuperFlo SF-N2-3/4A and Sta-Rite SuperMax HK2RAY6D-101L are both listed in the CA data and they both show a lower energy efficiency than the WFDS-3 when all three are run on low speed.

    While the CA data is hardly perfect, and does require some interpretation, which I'm not necessarily very good at, it does appear to give a different list.

    I'd like to get to have a better understanding of this issue, so we can give the best advice possible.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  2. Back To Top    #2

    Re: The most energy efficient two speed pump

    JasonLion,

    I had seen this that Mark posted in another forum back in February. The list is just a bit longer:

    Quote Originally Posted by Mark
    If you do not have a spa and/or other water feature, then the smallest pump possible will be more than enough for your pool. In fact, a two speed might be the best option. A variable speed pump will give you the best efficiency but two speeds are not bad either. Two Speed recommendations in order of highest to lowest efficiency:

    Hayward Super Pump SP2607X102S
    Pentair SuperFlo SF-N2-3/4A
    Sta-Rite SuperMax PHK2RAY6D-101L
    Pentair Pinnacle PFII-P2-1A
    Sta-Rite SuperMax PHK2RAY6E-102L
    Pentair SuperFlo SF-N2-1A
    Jandy Flo-Pro FHPM 1.5-2
    Hayward Super Pump SP2610X152S
    Pentair WFDS-24
    JPete
    Columbia, Missouri
    13600 gallons
    24' x 48" Round AGP. 1.5 hp/12 amp ecokleer pump. 22" ecokleer sand filter.

  3. Back To Top    #3
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,476

    Re: The most energy efficient two speed pump

    This explanation is going to be a little long so bear with me. The process is a little complicated.

    Physics tells us that the efficiency of a pump is highly correlated to the head curve which in turn is correlated to the THP of the motor. It takes more energy and a larger THP motor to produce higher flows and/or higher pressure, so the lower the head curve, the more efficient the pump will be. The actual efficiency of just the motor has an impact on energy use as well but for similar THP pumps, motors tend to have similar efficiencies. Higher THP motors tend to have better electrical efficiency (Watts/BHP) but because it takes more energy/GPM for a larger pump, this will dominate and the larger pump will end up using more energy/GPM even including a more efficient motor.

    With two speeds, most of the motors are generally standard efficiency (at least in the CEC list so far) so the efficiency of the pump (wet end) itself is will dominate the total efficiency of the pump and the differences between motors will have a much smaller impact. So again, the head curve drives efficiency more than anything else. So even if you did not have any CEC data, physics will tell you that a lower head curve pump will be more efficient than a higher head curve pump. So I tend to rely upon THP and the head curve to rank order the efficiency of a pump. However, I try not to ignore data either.

    Now back to the CEC data and how it is used. First, any pump that does not show a speed is full speed. Next, I don't have a lot of detail on how they do the measurements but there seems to be more measurement error at low speed than high speed but you might expect that depending on how the measurements are down between low and high speeds. One way to tell is that low speed should be within +- 1 GPM of half of the high speed GPM. However, in most cases, this is not true which leads me to believe that the low speed measurements were not necessarily done with a lot of precision. They should have adjusted the plumbing curve for high speed and then just set low speed without any plumbing adjustments. I believe they use a PSI gauge to measure the head loss for both high and low speed and we all know that there is higher error at lower PSI. Plus if they use flow meters to measure the flow rate, those also have significant error at low flow rates. So it isn’t a surprise that they probably have a lot of error at lower speeds.

    Another thing that I noticed is that not all of the measurements actually fall on the intersection of the pump head curve and the analytical curve definitions (A,B,C) for both high and low speeds. This means that the plumbing curve measurements may not be the same between pumps and/or speeds.

    And finally, the Whisperflo data is all screwed up and they swapped some of the models with others. The uprated versions of a pump should be the same as the equivalent full rated versions but they are not which doesn’t make sense. Also for some plumbing curves, higher THP pumps have better efficiency which again doesn’t make sense so that data must be “corrected” in order to be useful. I notified the CEC of this discrepancy and they are “looking into it”. However, I don’t think this is a real priority for them.

    So you might ask yourself, then what use is the data. Well it is useful to identify trends one of which is that the efficiency is highly correlated to the THP of the pump. This is why I use the THP and head curves as a proxy for efficiency because theory tells us this plus the general trend of pumps in the CEC data tend to flow this rule.

    Also, I use the CEC data in the PumpTools workbook but I do a lot of corrections to data that I believe is not correct. But the PumpTools workbook is primarily a learning tool and to give the user an idea of the energy use that a particular pump might use. For the most part I believe it is fairly accurate but there will be error in the calculations since the data source has a lot of errors.

    So on to my list. Given all of the above conditions, I came to the following conclusions:

    Hayward SuperPump 1 HP Uprated SP2607X102S
    Pentair SuperFlo 3/4 HP Full Rated SF-N2-3/4A
    Sta-Rite SuperMax 3/4 HP Full Rated PHK2RAY6D-101L

    Are all similar in efficiency simply because their head curves are similar, the THP are close although the SuperPump is lower which is why I give an edge to the SuperPump. But also, the CEC data on Curve-A at high speed shows the SuperPump to have a higher energy factor so that confirms the THP argument. Is it better at half speed? I don’t know for sure but I would assume so given the theory of pumps and motors.

    Next, the ¾ HP Whisperflo THP is about the same as the SuperFlo so in theory they should be about the same efficiency and only differ by the head curves. The Superflo head curve is slightly lower than the Whisperflo so it should have an advantage. The CEC data shows high and low speed as having a better energy factor for the SuperFlo SF-N2-1A than the WFDS-24 across most of the data points so that kind of confirms theory. I used the WFDS-24 instead of the 3 because it’s data looks more reasonable and what I would expect from the size pump. But again, they actually should be the same.

    So I am not sure I answered all of your question or just generated more but I am happy to clear up anything that may be confusing.

    BTW, if there is any doubt that the primary driver for energy use in a pump is flow rate, have a look at the following chart which shows the CEC Curve-A GPM vs Watts. It is pretty clear that the primary driver of energy use is flow rate which is determined by a pump's head curve and the plumbing curve.

    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  4. Back To Top    #4
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: The most energy efficient two speed pump

    I think you are over simplifying the CEC data. There are some problems with some of the numbers, but there are also indications that much of the data is of high quality, high enough quality to show effects which you have not taken into account in your models.

    Certainly there is a tight relationship between GPM and watts, but that doesn't mean it is consistent in all cases. The high efficiency motors are known to be about 15% better than the standard efficiency motors. Likewise not all wet ends are equally efficient, even though the designs are similar. Looking at pumps with identical GPM in the CEC data shows spreads of almost 40% in watts used between different pumps with identical flow rates. Even if some of that is measurement error, that is still a significant spread.

    Looking across just residential pool pumps there is a spread of about 30 times in THP (counting low speed as well as high), and obviously 40% variations in efficiency are not going to be very significant when looking across that range. But when comparing two pumps of more or less equal size a 40% variation in efficiency can make a huge difference, and can be more than enough to make a just slightly larger pump more efficient than a just slightly smaller pump.

    I went through the CEC data and looked at a number of pump families and most of them vary in exactly the ways you would expect. The WhisperFlo family had some of the most obvious exceptions. For example the WFDS-4 used more watts than the WFDS-6 and the WFDS-8 on all three plumbing curves on low speed and on two of the three on high speed, but had lower GPM than even the WFDS-3 on four of the six plumbing curves. Similarly, the WFDS-28 used fewer watts than the WFDS-26, but moved more water on all three low speed tests. That kind of inconsistency was unusual, and not seen in most of the other pump families.

    These errors do not show any sign of being caused by lack of precision in the measurements. There are a number of pump families that match up with theoretical numbers very well across a number of different sizes and plumbing curves. Likewise the errors tend to replicate across the A, B, and C plumbing curves, which would not be expected of random measurement jitter. Many of the errors strike me as transcription errors, results getting written down in the wrong slots, more than anything else.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  5. Back To Top    #5
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,476

    Re: The most energy efficient two speed pump

    My intent wasn't to discredit the data; I use it all the time. However, you just have to be careful when using it and make sure the measurements make sense. There are several cases where larger pumps have better efficiency factors than their smaller versions in the same model line and that cannot be not true.

    I really don’t think that they spent a lot of time in making sure that the measurements were all that accurate. The CEC objective was to measure each pump on one of three sets of plumbing curves. What this means is they had to adjust the head loss so the flow rate and head values fell on the plumbing curve and the pump’s head curve. This is not easy to do and requires a lot of iterations to hit it exactly. If you look up the flow rate from the data on the pump’s head curve, you will find that the GPM and head value usually do not fall on the plumbing curve that they were trying to hit. This means that the pumps were not measured on exactly the same head curve. In some cases, this was over 10% which to me is not insignificant. The error gets even worse at low speed so that is why I don’t have a lot of confidence in the low speed numbers. For example using Curve C which has a head calculation of:

    Head = 0.0082 * GPM^2

    ¾ HP SuperFlo 59 GPM on high, 30 GPM on low

    I believe this data since low speed is about ½ of high speed within 1 GPM. Plus the head value of 29' @ 59 GPM matches the head curve pretty well.

    WFDS-24 78 GPM on high and 42 GPM on low

    Low should be around 39 GPM. Also, if the measurement was done at 78 GPM, there should be 50' of head. However, from the head curve, 50' should be around 70 GPM not 78 GPM so that is wrong as well. So you cannot compare these two pumps since they were effectively measured on different plumbing.

    Also, the WFDS-3 data is so much different than the 24 when it should be identical, I don’t how you can trust either one really but if I had to choose one, it would be the 24.


    The high efficiency motors are known to be about 15% better than the standard efficiency motors.
    From the CEC data, the largest spreads I see is about 10% but most of the time for the same THP and class (single vs dual speed), motors tend to be less than 5% difference. One thing to keep in mind is that the same motors are available to all manufactures and most of them are AO Smith or Century so there really isn’t going to be too much of a difference in the motor efficiency between manufactures.


    Likewise not all wet ends are equally efficient, even though the designs are similar. Looking at pumps with identical GPM in the CEC data shows spreads of almost 40% in watts used between different pumps with identical flow rates. Even if some of that is measurement error, that is still a significant spread.
    According to the following articles and many like them, it is the specific speed design criteria of the pump which determines the hydraulic efficiency (WHP/BHP).

    http://www.lawrencepumps.com/newsletter ... 4_Sep.html
    http://www.mcnallyinstitute.com/07-html/7-03.html
    http://www.pumpfundamentals.com/help5.html

    So basically, if two pumps from two designers have the same specific speed, they will have the same hydraulic efficiency. As is noted in the article, the specific speed also determines the pump’s head curve so that is why I use the head curve as the determining factor for efficiency.

    A very good example of this is the SuperFlo pump. It was designed as direct replacement of the SuperPump and their head curves are very similar but so are their efficiencies (<1% difference). This is because they have nearly identical specific speeds and thus head curves. You can find many examples like this in the CEC data but the head curves must be the same in order to directly compare them.

    These errors do not show any sign of being caused by lack of precision in the measurements. There are a number of pump families that match up with theoretical numbers very well across a number of different sizes and plumbing curves. Likewise the errors tend to replicate across the A, B, and C plumbing curves, which would not be expected of random measurement jitter. Many of the errors strike me as transcription errors, results getting written down in the wrong slots, more than anything else.
    I think most of the error comes from the technician missing the plumbing curve.

    However, that is not what concerns me the most. The biggest errors are in the Whisperflo series which does not give me a lot of confidence in those measurements or even if it is a data entry problem then which is the correct data. The up rated and full rated versions should be identical but the error there is just ridiculous. So I am not sure how you can trust any of the Whisperflo data.

    But just comparing the head curve and calculating the specific speeds of both the SuperFlo and Whisperflo tells me that the SuperFlo will be more efficient than the Whisperflo.

    So I guess the bottom line is this data is open to some interpretation. But one thing is for sure, I am not sure I would hang my hat on the Whisperflo data. Overall, it just doesn’t make sense to me.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  6. Back To Top    #6
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: The most energy efficient two speed pump

    Quote Originally Posted by mas985
    One thing to keep in mind is that the same motors are available to all manufactures and most of them are AO Smith or Century so there really isn’t going to be too much of a difference in the motor efficiency between manufactures.
    For single speed and dual speed pumps, everyone chooses from the same pool of motors, choosing between energy efficient motors and standard motors. Not all pumps use the new energy efficient motors, presumably because they are more expensive. Quite a number of each kind appear on the list. That certainly accounts for some of the measured efficiency variation.

    Quote Originally Posted by mas985
    What this means is they had to adjust the head loss so the flow rate and head values fell on the plumbing curve and the pump’s head curve. This is not easy to do and requires a lot of iterations to hit it exactly.
    Do you know how they do that? Casually, I would think that this would be easy to do, just get a pipe of some fixed size and length that corresponds to the plumbing curve you want to model and use it for all of the tests. SInce that is nothing like what you wrote, I assume that there is something I am not understanding here.


    I totally agree, the WhisperFlo data in particular is wildly inconsistent, as I mentioned earlier.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  7. Back To Top    #7
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,476

    Re: The most energy efficient two speed pump

    I believe that they use a throttling valve and PSI gauge to determine the head loss as that is more of a standard in the industry. This can be a very tedious effort and if the tech is bored at all, they may have made some short cuts. Here are a couple of references for the testing:

    http://standards.nsf.org/apps/group_pub ... %20CEC.pdf
    http://standards.nsf.org/apps/group_pub ... nt_id=8332
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  8. Back To Top    #8

    Re: The most energy efficient two speed pump

    So a lot of these posts are way over my head but is the SP2607X102S still at the top of the list for energy efficiency?
    24,000 G, Sand, IG, Vinyl

  9. Back To Top    #9
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: The most energy efficient two speed pump

    Yes, given the data available, the Hayward SuperPump 1 HP Uprated SP2607X102S appears to be the most energy efficient two speed in-ground pump at the moment. All of the variable speed pumps should be even more efficient, but they cost significantly more up front and will not pay back the extra costs unless your electric rates are relatively high.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  10. Back To Top    #10

    Re: The most energy efficient two speed pump

    Any idea how SP2707X102 measures up?
    24,000 G, Sand, IG, Vinyl

  11. Back To Top    #11
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: The most energy efficient two speed pump

    Equivalent test data for the SP2707X102 is not available. It uses a larger motor but has a similar head curve, so I can't say for sure either way.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  12. Back To Top    #12
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,476

    Re: The most energy efficient two speed pump

    I think that I may need to clarify some of my statements about these pumps. First, the pump lists that I have previously posted, can change order depending on the plumbing assumed. Some of the pumps have better energy factors for one curve while others are better on other curves. This is one reason why the PumpTools workbook may be a better way to compare pumps so that you can use your exactly plumbing situation to compare the pumps. However, it is also important to understand that I use a lot of approximations to "model" these pumps and it uses the same flawed CEC data so there is some error involved with the calculations but at this point it is the best I can do.

    Next, for most pumps, the flow rates that are shown in the CEC data seem to be within about 5% of the actual desired plumbing curve, except for some of the Whisperflo pumps. This is probably not so bad when you consider that they are using pressure gauges and flow meters to make the measurements. So I would have to say that if two pumps have energy factors within 5% of each other, then I would probably consider them to be the same energy factor.

    However, there are some important differences between the pumps which might influence a decision to go with one pump over another. Even though the Whisperflo 24 has about the same Curve-C energy factor as the SuperFlo, it does so with 30% more flow rate which is pretty impressive. If that higher flow rate is needed to turn the pool over faster, then that should also be considered. During daylight hours, I think it is important to run the pump for circulation and would probably steer people to the smaller pumps for smaller pools with smaller plumbing and the Whisperflo for larger pools with larger plumbing. The Whisperflo might turnover smaller pools in less than 8 hours on low speed so one would need to run it longer making it less efficient than the smaller pumps.

    However, the higher flow rate of the Whisperflo might be desired for better skimmer on pools with two skimmers. Also, because the SuperFlo has a lower head curve than even the SuperPump, I might steer people away from that pump if they had solar but it depends on the setup.

    All of these things need to be considered when deciding on a pump. But in general, simply chosing the smallest pump in a product line will result in fairly good energy efficiency.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

  13. Back To Top    #13

    Join Date
    Aug 2008
    Location
    Dallas (Plano), TX
    Posts
    41

    Re: The most energy efficient two speed pump

    This thread's dialog was very helpful reading. Much appreciated.

    Best regards,

    Bill
    30 KGal IG plaster pool with diving board & spa, built '96; 2 speed (2.2/0.28 THP) AO Smith B2983 hi efficiency motor for circ (3 skimmers w/ 1.5" lines & drain w/ 2" line) (replaced original 1 speed Sta-Rite Max-E-Glas II 2.0 THP pump in 2011); waterfall w/ Sta-Rite Max-Glass II 2.5 THP pump w/ 2.5" lines, Polaris 280 pressure-side cleaner w/ 3/4 HP pump, Sta-Rite System 3 Vertical Grid 53 sqft DE filter, AquaLink RS6 P&S w/ 52 pin Rev K.33 controller, Rainbow offline tri-chlor erosion feeder, 450 KBTU/hr Rheme gas-fired heater, Dallas climate, 10/kwh current electric rate, energy monitoring system at http://www.welserver.com/WEL0043

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •