Converting to a two speed motor

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J

jkapp

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Aug 20, 2007
28
Hunterdon County, NJ
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!!
 
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!
 
rjg3435 said:
what's the advantage of a two-speed versus a single-speed motor?
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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.

svenpup said:
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).
Click to expand...
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.
 
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.
 
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!
 
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.
 
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.
 
jkapp said:
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.
Click to expand...

I am interested in a flow meter, do they make them that will read less than 30 GPM?
 

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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
 
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.
 
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
bolinas said:
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.
Click to expand...
 
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