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Thread: Balky pump - thermal cycling

  1. Back To Top    #1

    Join Date
    Sep 2014
    Location
    Fort Lauderdale, FL
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    144

    Balky pump - thermal cycling

    So we bought our house last July, and I noticed as soon as we moved in (August?) that the pool pump tends to cycle on and of periodically. It's a single speed 3/4hp on an unknown pump body. I immediately ordered a replacement pump motor (AO Smith, 48Y, 3/4hp) to have on hand for when it goes. And then I decided to wait till the old pump died.

    Here's where it gets interesting. It's been about 6 months now and the old pump is still doing it's thing. It isn't squealing, or doing any of the other things that you would associate with a dying pump. I've checked the voltage, it's properly wired and running at 240V. Nothing wrong there. While I had the motor cap/cover off (you know, the one that covers the electronics on the end of the motor), I noticed something else interesting. With the back cover removed, it runs flawlessly, and does not cycle off and on. Put the cover back on, it starts cycling like it's overheating again.

    Is there any chance the thermal switch on the motor has gone bad, and is toggling off unnecessarily, or at a lower temperature that it should? If so, is there anything I can do about it? Or should I just go ahead and put on the new motor? I do not have a new shaft seal or frame gasket on hand, but I imagine it would be recommended to replace these if I swap motors?
    15k in-ground plaster, Hayward C900 cartridge, 3/4hp single speed pump, Barracuda G2 cleaner, TF-100

  2. Back To Top    #2
    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: Balky pump - thermal cycling

    It is possible that the overheating cutout is malfunctioning. There are some more complex possibilities, but it is usually the simple and obvious things that break. It is fairly easy to replace an overheat switch.

    If/when you replace the entire motor, you will certainly need a new shaft seal. The frame gasket is usually fine to be reused.
    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

  3. Back To Top    #3

    Join Date
    Sep 2014
    Location
    Fort Lauderdale, FL
    Posts
    144

    Re: Balky pump - thermal cycling

    Any idea where I would source an overheat switch, if I went that route?
    15k in-ground plaster, Hayward C900 cartridge, 3/4hp single speed pump, Barracuda G2 cleaner, TF-100

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