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Thread: Two speed or variable speed?

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    Two speed or variable speed?

    I have a 30k plaster pool with a Jandy RS-8, JVA, SWG, booster pump Polaris. Current setup is pool/spa, single motor, single speed. The pump is making noise and in fact doesn't power the spa very well. My pool guy has suggested a continuously running variable speed pump would be a good idea as it would keep the water circulating all night on low speed, and then for shorter periods during the day on high. Currently I run it 6 hours twice a day when the temps are above 60 degrees.

    I was told that the Jandy RS panels require a separate module to run a variable speed pump, and only the Jandy variable speed pumps work well with the RS. But, in reading this thread, it looks like a two speed pump might be fine. Perhaps a two speed is different, as noted by Bill (a0128958), who has integrated it into his RS-6? Could someone recommend some high efficiency brands and how to hook into the RS-8?

    Finally, how long do you all recommend running the pump each day in warm weather, and how long in cooler weather?


  2. Back To Top    #2

    Join Date
    Aug 2008
    Dallas (Plano), TX

    Re: Advice on equipment replacement

    I can't speak to the continuously variable pool pumps - while they do have all of the benefits as advertised, they're so expensive here, at least here in the Dallas area, that it just doesn't yet make sense to purchase one versus using 2-speed pumps.

    In the Summer of 2011, my 2.0 THP single speed filtration pump motor stopped working after over 15 years of service. I replaced it with a 2-speed motor.

    At the time of replacement, my 12 month rolling average for total pool operating energy was on avg 18 kWh/day.

    Fast forward to now, and with no other replacements done since the 2011 change out, and no changes to the operating schedule of the various pumps (other than to double the filtration run time to accommodate the low speed of the 2 speed motor), my 12 month rolling average for pool operating energy is 10 kWh/day, an 8 kWh/day reduction (improvement).

    By simply changing out a single speed for a 2 speed pump motor, operating cost improved by 44%. 8 kWh/day savings at 12 cents/kWh is $350/year savings. Since I did the work myself, I paid for the pump replacement easily in 6 months.

    Cost of the 2-speed motor was approximately $200, perhaps $30 more expensive than a replacement single speed motor. Add in another $35 for a 2-speed relay for my Jandy RS-6, and another $15 for misc supplies (i.e. wire to/from the new relay and the new motor). Total incremental cost was about $80 (assuming you're at the point where you have a broken motor). And annual savings is $350.

    When it's time to replace single speed motors, and if you have an accommodating automated controller (i.e. I have a Jandy AquaLink RS6), replacing single with a 2-speed motors is a 'no brainer.' Even the revised run time is easy to figure out. Just double the run time to get the same filtration on the low side of a 2 speed motor. (I.e. I used to filter for 8 hours per day - now I filter for 16 hours each day.)

    The nice fancy variable speed motors are going to accomplish the same thing. In fact, probably a little more savings than 2-speed motors, as they run more efficiently using permanent magnets. But the cost is so much higher than 2-speed motors such that if overall cost of ownership is your objective than it's hard to ignore 2-speed motors.

    Best regards,

    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

  3. Back To Top    #3

    Re: Advice on equipment replacement

    Thanks very much! I think I have a 1.5 or 2 HP pump now; if I go with a higher HP pump, would I get better spa performance? The jets seem a little weak with the current one. What is the highest HP 2 speed pump available that one can reasonably/safely use?

    Also, what is the proper relay and does it just plug in? I have a rev QQ RS-8 pool/spa combo.

  4. Back To Top    #4

    Re: Advice on equipment replacement

    So here's some more info. The pump is actually an AO Smith 2.5 hp single speed pump, attached to a Pentair Challenger 345201 PMP CHII N1 1.5F head/impeller. This shows the specs on the pump series.

    Would you suppose the AO Smith 2 speed would just drop in, or would it be better to go with a Pentair 2 speed 2.5 hp pump? A couple of other questions: Is this head not designed for that level of power, and is that necessary if I want to power spa jets etc?

  5. Back To Top    #5
    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Two speed or variable speed?

    Getting a two speed or a variable speed is partly a question of how much electricity costs where you are. It takes fairly high electrical rates, $0.20/hwh or more, to justify the initial expense of a variable speed.

    The least expensive thing to do is to get a two speed motor that will fit your existing pump.

    There is no need to run the pump 24/7, mostly it is just a waste of money. Most pools are fine with four to six hours of total run time, even on low speed, less than that when the water is cold.

    You will need a large pump to get good jet action in the spa. That is one big advantage for a variable speed, you can dial in exactly the amount of water you want when running the spa.
    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

  6. Back To Top    #6

    Re: Two speed or variable speed?

    Great info guys!
    16x32 in-ground vinyl-lined pool
    Hayward 1.5 hp 2 speed pump
    Hayward 24" Pro-Series High rate sand filter
    Pentair Intellichlor IC-40 SWG, Pentair multi-color LED light.
    TF-100 Test Kit (the best test kit EVER!!!! If you don't have one, get one NOW!)

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