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Thread: Converting to a two speed motor

  1. #1
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    Converting to a two speed motor

    I currently have a single-speed Jandy SHPF1.5 that I want to convert into a two-speed for the energy savings. I believe the SHPF1.5 has a A.O. Smith B842 motor, so it appears that the B983 is proper two-speed match. Does that look correct?

    My heater and SWG need a 30 GPM flow. Based upon my calculations, I'm going to be cutting it close at low speed - about 36 GPM. Should I consider upsizing the motor one model to the B984 or will that just give me a less efficient setup?

    Last, I've been searching the Internet for a source for A.O. Smith or Emerson motors, but I don't recognize any of the stores. Does anyone have recommendations on where to buy pool motors?

    Thanks and Happy Spring!!
    31,000 gal gunite/Pebblesheen pool w/spillover spa, 2-speed 1.5 HP filter pump, 3 hp spa jet pump, 2 hp sheer decent pump, blower, DE filter, Jandy automation and SWG, Jandy 400K BTU gas heater, Polaris 280 cleaner with booster pump.

  2. #2
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    Re: Converting to a two speed motor

    Being a pool newbie, what's the advantage of a two-speed versus a single-speed motor? My motor is working fine, but when it goes (and it will someday) this info will be handy.

  3. #3
    Senior Member svenpup's Avatar
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    Re: Converting to a two speed motor

    The B983 looks correct if you do indeed have a B842 currently (1.5hp - 56y frame - square flange).

    I recommend the B2983 rather than the B983. The "New Centurion" line has an energy efficient high AND low speed. The service amps on low are less than half (1.6 vs 3.5) so you will realize even more savings (especially since you will be on low for much longer duration).

    I just converted to two speed and used a B2980, which is the 3/4hp version of the "New Centurion".

    I ordered mine from a1poolparts.com and was very pleased with the price and service.

    There are several other sites that sell motors, so use google or bing.

    Don't forget to get the correct shaft seal since you will want to replace it, and consider replacing the critical o-rings and gaskets too. I did the whole set, since I was already going to be in there. It was only an extra $10 or so to get them all.

    Good luck!
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    • 17,500 gallons - In Ground - Plaster - Hayward Swimclear 3020 Cartridge Filter - Sta-Rite Max-E-Glas Main Pump upgraded with A.O. Smith B2980 E-Plus New Centurion Two-Speed Motor - Polaris 280 Cleaner with Polaris PB4-60 Booster Pump - TightWatt2 Timer - Taylor K-2006 Test Kit - Pool Pilot Digital Nano SWCG

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  4. #4
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    Re: Converting to a two speed motor

    Quote Originally Posted by rjg3435
    what's the advantage of a two-speed versus a single-speed motor?
    From A.O.Smith's website:

    Common sense might tell you that if you reduce the speed of your swimming pool pump motor by one-half, the pump will pump half as much water while working half as hard. In fact, the pump will pump half the amount of water, but the load on the motor is reduced much, much faster or, more precisely, by the cube of the speed. Even though it takes twice as long to pump the same amount of water, the dramatic drop in the amount of horsepower required to do it saves a lot of electricity.

    Quote Originally Posted by svenpup
    I recommend the B2983 rather than the B983. The "New Centurion" line has an energy efficient high AND low speed. The service amps on low are less than half (1.6 vs 3.5) so you will realize even more savings (especially since you will be on low for much longer duration).
    This is huge - thank you! The only reason that I'm doing this is energy savings. It would have driven me nuts if I installed the B983 and later realized that could have cut my energy cost by another 50% if I had only installed the B2983.
    31,000 gal gunite/Pebblesheen pool w/spillover spa, 2-speed 1.5 HP filter pump, 3 hp spa jet pump, 2 hp sheer decent pump, blower, DE filter, Jandy automation and SWG, Jandy 400K BTU gas heater, Polaris 280 cleaner with booster pump.

  5. #5
    Senior Member mas985's Avatar
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    Re: Converting to a two speed motor

    The B983 has a higher low speed HP rating than the B2983 (0.25 HP vs 0.19 HP) which accounts for some of the lower amp rating (~25%). Both motors have a service factor amps rating which is rated at the label SFHP. Since both motors will have exactly the same load, the actual savings of the B2983 is likely to be only about 25% which is still pretty good. The impeller load should require less than 0.19 BHP so either motor would work just fine but the B983 would allow for higher loads should they ever exist which they won't.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  6. #6
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    Re: Converting to a two speed motor

    Just wanted to close the loop on my original post and report that I finally pulled the trigger. Thanks to TFP, it was a piece of cake. I replaced the motor on my Jandy pump with A.O. Smith's B2983 from a1poolparts as was recommend by svenpup. I was pleased with them as well.

    I was originally concerned about my low-speed flow rate. In the end, my flow rate is well below 40 GPM (which is the minimum on my B&W flow meter), but it must be above 30 GPM because my SWG and heater aren't complaining about flow rate.

    One unexpected outcome is that my flow rate on high-speed is significantly higher than it was with the stock motor. Although both motors have a BHP of 2.2 HP and a speed of 3450 RPM, the Jandy (Emerson) motor gave me a flow rate of 70 GPM right before the motor swap. The A.O. Smith motor is giving me about 80 GPM. I can't figure that one out...

    I couldn't have done this without TFP!
    31,000 gal gunite/Pebblesheen pool w/spillover spa, 2-speed 1.5 HP filter pump, 3 hp spa jet pump, 2 hp sheer decent pump, blower, DE filter, Jandy automation and SWG, Jandy 400K BTU gas heater, Polaris 280 cleaner with booster pump.

  7. #7
    Senior Member mas985's Avatar
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    Re: Converting to a two speed motor

    If you didn't change the impeller, then the flow rates should be about the same. It could have been that the old motor had a very high slip rate due to bad bearings but it would have to increase to about 16% which is very high. Did you happen to clean the impeller when swapping the motors?

    But if your new high speed flow rate is close to 80 GPM, then low speed should be about 40 GPM.
    Mark
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study
    18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, 450 sq-ft EPDM Solar Panel, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner, DIY Acid Dosing

  8. #8
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    Re: Converting to a two speed motor

    I did clean the impeller, but it was pretty clean to start with. But now that you mentioned that, I did also clean the pump basket. There was some gunk stuck to the wall of lower half of the basket, but the wall on the upper half was clean. I never would have thought that just having a portion of the basket dirty could make that much difference in flow, but I bet that's what made the difference. Thanks for helping to explain it.
    31,000 gal gunite/Pebblesheen pool w/spillover spa, 2-speed 1.5 HP filter pump, 3 hp spa jet pump, 2 hp sheer decent pump, blower, DE filter, Jandy automation and SWG, Jandy 400K BTU gas heater, Polaris 280 cleaner with booster pump.

  9. #9

    Re: Converting to a two speed motor

    Quote Originally Posted by jkapp

    I was originally concerned about my low-speed flow rate. In the end, my flow rate is well below 40 GPM (which is the minimum on my B&W flow meter), but it must be above 30 GPM because my SWG and heater aren't complaining about flow rate.
    I am interested in a flow meter, do they make them that will read less than 30 GPM?
    16,000 Plaster/Gunite - Pentair FNS Plus Fiberglass D.E. Filter
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    A.O. Smith Two Speed Motor B983 - Solar Blanket - Polaris 380
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  10. #10
    Senior Member dremin2flyhi's Avatar
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    Re: Converting to a two speed motor

    Key Instruments has them... and I think you can order them from Grainger... here is a link to the manf web site
    http://www.keyinstruments.com/products/ ... es-PR.html
    24' x52" ABG (13,500)
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  11. #11
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    Re: Converting to a two speed motor

    svenpup,

    I too am going to the B2980. I ordered it and it just came in. I didn't order and o rings or seals. Any suggestions about what I need to do there appreciated. I'm new to pool ownership and have really been to school recently. My pump is a Jandy whisperflow and the motor I'm replacing is a 1/2 horse so the 3/4HP B2980 should help with vacuuming on high speed and lower operating cost on low speed - at least that's my theory. I also bought a new 2 speed relay for my Jandy Aqualink RS controller. Seems the wiring should be pretty simple, but I'm no electrician. I hope to just follow the same pattern. Any clues appreciated.

    Bob
    14,000 gallon plaster IG vanishing edge pool with cartridge filter with a two speed 3/4 HP converted whisperflow pump on the filter and a 2HP single speed whisperflow on the vanishing edge.

  12. #12
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    Re: Converting to a two speed motor

    I am happy to report a successful replacement of my single speed 1/2 HP motor in my whisperflow pump with a new 3/4HP 1/8HP two speed motor. It is a major improvement in energy savings as I operate in low speed most of the time and a major improvement in suction over the single speed, when operating at the 3/4HP highspeed setting for vacuuming. It's also much quieter in high speed and you hardly hear the low speed. Perhaps the biggest help of all was removing the rusted nail and rocks from the impeller! I decided not to change out all the seal parts as they were in pretty good shape.
    14,000 gallon plaster IG vanishing edge pool with cartridge filter with a two speed 3/4 HP converted whisperflow pump on the filter and a 2HP single speed whisperflow on the vanishing edge.

  13. #13
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    Re: Converting to a two speed motor

    Just purchased the same motor. Did you end up replacing with a standard 5/8" seal? What did you use for the low to high speed switch? Thanks for any help!
    Jim
    Quote Originally Posted by bolinas
    I am happy to report a successful replacement of my single speed 1/2 HP motor in my whisperflow pump with a new 3/4HP 1/8HP two speed motor. It is a major improvement in energy savings as I operate in low speed most of the time and a major improvement in suction over the single speed, when operating at the 3/4HP highspeed setting for vacuuming. It's also much quieter in high speed and you hardly hear the low speed. Perhaps the biggest help of all was removing the rusted nail and rocks from the impeller! I decided not to change out all the seal parts as they were in pretty good shape.
    Jim
    15k inground pool/spa
    3/4hp Whisperflow
    Cartridge filter (Hayward)
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