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Thread: What is the shelf life for a run capacitor?

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    bradntyler's Avatar
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    What is the shelf life for a run capacitor?

    Good morning all !!
    My run capacitor on my main pump has gone out (RD-25-370), and, after buying one today from the local pool supply house (all the electrical houses do not carry this model), I want to go to Amazon and buy one for a spare. Does anyone know if these run cap's have a shelf life just sitting in a garage in East Texas ??? This forum has been a life saver for my troubleshooting questions. Thanks in advance for your help.
    24k, vinyl, sand, IG with 1HP Hayward Super II
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    Mod Squad JohnT's Avatar
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    Re: What is the shelf life for a run capacitor?

    Yes, they do have a shelf life. About 2 years, and they should be stored at less than 104. They may last much longer, but you can't count on it. I would store them in an air conditioned space. Warmer temperature shortens their life.

    The old ones with hazardous chemistry lasted forever, but newer ones don't last long. I usually wait a year after replacing one and then order another one to keep on hand.
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    bradntyler's Avatar
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    Re: What is the shelf life for a run capacitor?

    Thanks JohnT !!! I appreciate your quick response.
    24k, vinyl, sand, IG with 1HP Hayward Super II
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    mas985's Avatar
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    Re: What is the shelf life for a run capacitor?

    I think the gel electrolytics have a 2 year shelf life but the polymer versions used in induction motors are usually longer than that.

    But you can greatly extend the life of both capacitors if you alternate use every 6-12 months. It is the shelf life that is much shorter because the plates can deform over time and when energized, they will re-form.
    Mark
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    Mod Squad JohnT's Avatar
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    Re: What is the shelf life for a run capacitor?

    Quote Originally Posted by mas985 View Post

    But you can greatly extend the life of both capacitors if you alternate use every 6-12 months. It is the shelf life that is much shorter because the plates can deform over time and when energized, they will re-form.
    Not a bad thought. If you winterized you could just swap caps every spring.
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    Re: What is the shelf life for a run capacitor?

    Quote Originally Posted by bradntyler View Post
    Good morning all !!
    My run capacitor on my main pump has gone out (RD-25-370), and, after buying one today from the local pool supply house (all the electrical houses do not carry this model), I want to go to Amazon and buy one for a spare. Does anyone know if these run cap's have a shelf life just sitting in a garage in East Texas ??? This forum has been a life saver for my troubleshooting questions. Thanks in advance for your help.
    Problem is the origin of mfg., China or Mexico = Cheap , junk, replace often, no quality control.
    USA made = higher price and typically higher quality when dealing with capacitors.

    Today capacitors have become a common replacement item, where 30 years ago, they would last as long as the equipment it served. They were ~ 5 times the size and dissipated heat much better.
    As size and production costs reduced, oil was replaced with water based gel, the plates had to become closer, and dielectric materials were improved to increase capacitance.

    If you can, get an oil filled capacitor that will fit properly in the pump housing, the mfd. size should be what mfg specs. The voltage can be equal or larger, but never lower. A residential run capacitor is typically rated at 370 or 440v. This is because it is subjected to higher voltages of compounded back emf as speed increases, compared to that of input line voltage of 240v or 120v.

    With run capacitors, it's best to keep the operating temperature down and fluid flow restriction down. As flow restriction increases, so does the voltage across the capacitor. This is due to higher rpm at a lower load. So, if you're moving less water due to flow restriction, the centrifugal type pump motor will spin faster creating greater back emf, and higher run cap voltage.

    A great example of this is a vacuum cleaner. Ever wonder why it gets so loud when you clog the nozzle? The RPMs increase far above normal operation or "designed slip".
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