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  • Page 2 of 2 FirstFirst 12
    Results 21 to 24 of 24

    Thread: Energy Efficient Pumps

    1. #21
      danbo is offline Senior Member
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      I've been on/off playing with pumps for years. The engineer in me tells me that you don't get anything for nothing. I keep looking for the book on this: "Pulp Fiction vs Pump Fact". A pump is doing work which is basically pushing a volume of water to a required head. At the other side of the equation you input electrical energy. Despite claims of 'more efficient pumps on the market', pumps have been with us since probably Roman times and before. The science and engineering was more or less mastered in the 19th Century. Fine tweaking since then. Pump efficiency is probably around 90-95%. ie....put in 100W of electricity, get 95W of energy to move your water on the output side. The problem is that most folks don't know what they need on the 'output side'....what is the 'head' the pump will be seeing when it pumps the XYZ m3/hr that you want. We err therefore, and buy a pump that is too big...fitting a throttle valve on the outlet. On one of my pumps I've gone from 0.75kW rating (1HP) to 0.4kW and now I find I can do with 0.15kW. This is a huge saving on power considering the pump is on 24/7. In terms of flow to the pond, I guess the 0.4kW with throttle valve on the outlet was the 'best', giving me about 11-12m3/hr. The 0.15kW pump with throttle valve full open gives me about 9m3/hr. I'm not sure the fish know the difference between 9 and 12m3/hr, but for sure I see it in my utilities bill.... Many pumps have max heads far too high to be considered for Koi ponds. (my 0.75kW pump had a max head of over 18m! Anything above 8-10m max head rating on the pump, I'd suggest is a pump designed for an application other than a Koi Pond.

    2. #22
      batman's Avatar
      batman is offline Senior Member
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      Not quite. Electric motors used on pond pumps vary from the 60s% on low end ones to slightly over 90% efficiency on the motor itself . Pond pump designs also vary per head range. Often pumps are designed not for max performance but for maximum ease of manufacturing and maximum profits. Available manufacturing machinery, labor and materials playing a big part.

      It's a racket with most manufactures embellishing posted performance. Often choices are made on the mfg lying the most. The only pond pump specifications I trust are the Flow Friend pumps adhering to EU pump performance standards.

      Through the years every pond owner that correctly installed a quality flow meter got less flow than their estimate (embellished guess).
      Last edited by batman; 05-04-2021 at 08:42 PM.
      The real Batman wears polyester! Don't be fooled by the plastic imposter.

    3. #23
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      Quote Originally Posted by danbo View Post
      I've been on/off playing with pumps for years. The engineer in me tells me that you don't get anything for nothing. I keep looking for the book on this: "Pulp Fiction vs Pump Fact". A pump is doing work which is basically pushing a volume of water to a required head. At the other side of the equation you input electrical energy. Despite claims of 'more efficient pumps on the market', pumps have been with us since probably Roman times and before. The science and engineering was more or less mastered in the 19th Century. Fine tweaking since then. Pump efficiency is probably around 90-95%. ie....put in 100W of electricity, get 95W of energy to move your water on the output side. The problem is that most folks don't know what they need on the 'output side'....what is the 'head' the pump will be seeing when it pumps the XYZ m3/hr that you want. We err therefore, and buy a pump that is too big...fitting a throttle valve on the outlet. On one of my pumps I've gone from 0.75kW rating (1HP) to 0.4kW and now I find I can do with 0.15kW. This is a huge saving on power considering the pump is on 24/7. In terms of flow to the pond, I guess the 0.4kW with throttle valve on the outlet was the 'best', giving me about 11-12m3/hr. The 0.15kW pump with throttle valve full open gives me about 9m3/hr. I'm not sure the fish know the difference between 9 and 12m3/hr, but for sure I see it in my utilities bill.... Many pumps have max heads far too high to be considered for Koi ponds. (my 0.75kW pump had a max head of over 18m! Anything above 8-10m max head rating on the pump, I'd suggest is a pump designed for an application other than a Koi Pond.
      Well, the engineer in you should also know that you can design for different parameters, you can oput a corvette engine on a lawnmower and it will never bog down, but you only need a little briggs and stratton to turn a 22" blade fast enough and with enough torque to cut the blades of grass in it's path. The same is true with pumps, the design of the impeller can be optimized for PSI or for volume (high head/Low head) The speed of the engine matters, lower RPMs for higher volume design pumps, and the design of the actual motor and the copper windings, quality of permanent magnets and alignment of the rotor to the magnetic fields... you don't ever get something for nothing, but you are often wasting something.
      Koiphen member since 05-13-2004

    4. #24
      danbo is offline Senior Member
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      Agree on the efficiency. My error. Not sure where I picked up the 90-95% efficiency from (maybe a few beers when I wrote that post last night). Correct that for well designed pumps, operated close to their best operating point, the efficiency may be 60-70%. Agree also, lots of cheap stuff out there...! A good starting point in pump selection is here: https://www.engineeringtoolbox.com/p...wer-d_505.html Most folks have a reasonable idea of the flow they require (turnover the pond volume in x hrs?). Plotting the system curve for the installation (height the water has to be pumped to, length & diameter of downstream line etc) to get the operating head is a different matter. Gotta go golf now, but attached is a pic of an Excel file I put together with various pump curves plotted against my calculated 'system curve' (green curve) for my installation. This 'river pump' pumps to the head of two rivers which flow back to the pond. River head is about 1.2m above the water inlet head of the pump hence the green curve starts 1.2m up the head axis. Not sure if this helps, but happy to elaborate if it does.

      Name:  River Pump Curves.JPG
Views: 49
Size:  36.8 KB

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