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Thread: Starter capacitors on electric motor?

  1. #1
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    Default Starter capacitors on electric motor?

    My giant air compressor is acting like it can't pull the load. I checked to make sure it spins freely and now suspect the starter capacitors need to be replaced. It is a 2.5 hp motor and has two capacitors. Oddly, they are not the same size. One is like 216-257 mfd 270vac and the other is a 50 mfd 400vac. It may have been replaced with the wrong capacitor by the previous owner. Is it normal to have two different sizes on one motor?

  2. #2
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    Yep - a starting and a running capacitor. A lot of times they'll be in once can, though. There's usually a schematic on the inside of one of the panels that should show the correct size for each.

    Is it your compressor motor that's not running or is it the condenser fan motor?
    Ephesians 2 : 8-9



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  3. #3
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    BTW - I am not a AC guy but I can usually fix my own, unless it's in the Freon loop.
    Ephesians 2 : 8-9



    Charles Barkley: Nobody doesn't like meat.

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    Just take em out and replace em. $10-12 and 5 min

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    This is the motor on a shop air compressor, not an HVAC unit. I called it a 2.5 hp but it's actually a 8.5 hp. It doesn't have a schematic that I've seen. I have replacement capacitors ordered but wanted to ask if it was normal to have different sizes on the same motor. Thanks.

  6. #6
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    The larger is for starting and the smaller is for running.
    You can go with a bigger (number wise) capacitor, but not smaller.
    Last edited by Bownut; 03-11-2019 at 08:42 AM.

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    Sorry - I can't read...
    Ephesians 2 : 8-9



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    Pm sent

  9. #9
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    I am familiar with the flux capacitor, but not much help otherwise
    Quote Originally Posted by Glenn View Post
    Does Elton John know you have his shotgun?

  10. #10
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