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Thread: Replacing pump motor with a 2 speed

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    VoR's Avatar
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    Jun 2009
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    Replacing pump motor with a 2 speed

    The 1/2HP Whisperflo (motor is an AO Smith QC1052 from what I have gathered) has spun the rear bearing ( I took off the rear inspection cover and witnessed it spinning in the race) and makes a pretty bad grinding noise, I lubed it and its a little quieter but I know it will fail before too long.

    I am considering replacing with a 2 speed for energy and noise reasons. What do I need to know about replacing my motor with a 2 speed one? Since my current one is a high efficiency one so I need to up the HP if the new one is not? Any issues with running this particular pump at the lower RPMs of low speed?

    Thanks in advance.
    9000 Gallon Gunite Pool
    Pentair 1/2 HP Whisperflo Pump
    Pentair DE Filter
    Kreepy Krauly

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    JasonLion's Avatar
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    Re: Replacing pump motor with a 2 speed

    Replacing the motor with a suitable two speed motor is just fine. You need to match the brake HP (listed HP times service factor) exactly unless you also replace the impeller to match the new motor rating. High efficiency motors are difficult to find in two speed (and also difficult to find as small as 1/2 HP), so a two speed is likely to use more electricity on high than you existing motor used to. Of course it will use less electricity on low speed.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    VoR's Avatar
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    Re: Replacing pump motor with a 2 speed

    Yes, I was calculating that and I get .5 with a SF of 1.90 = 0.95

    The lowest HP 2 speeds seem to be 3/4 so I'd probably have to get the WFE-3 impeller to run on it. .75 * 1.67 = 1.15.

    The EE 1/2 motor like I have looks to be around $200 new, the new 2 speed EE motors are $280 + $60 for the impeller so I'd bo looking at around $150 extra to get the 2 speed running but the sound may be worth it. I just wish I knew how quiet it would be with good bearings. There may be some energy savings too, but probably minimal since the motor is larger...

    EDIT: and a switch...need to factor that cost in too
    9000 Gallon Gunite Pool
    Pentair 1/2 HP Whisperflo Pump
    Pentair DE Filter
    Kreepy Krauly

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