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  1. #27
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    774
    Well over 90% of the time, the run caps you will encounter on a day-to-day basis discharge themselves very quickly through the motor windings when power is removed. Most start caps have a bleeder resistor. It isn't good for an electrolytic capacitor to discharge it by direct shorting (it harms the plates and the electrolyte between them), but since most all caps are already discharged when you put your screwdriver across them anyway it doesn't really matter.

  2. #28
    Join Date
    Dec 2011
    Location
    bedford ind
    Posts
    1,085
    Should not direct short the cap terminals, or hook your meter to a charged cap. If you don't want to buy a resister, take one off a used or old start cap. 15k ohms is plenty. Discard the altered cap in a responsible way, please!

  3. #29
    Join Date
    Dec 2011
    Location
    Ozarks of Missouri
    Posts
    32
    As an electrician for 20+ years, my 2 cents: big enough start and run capacitors, if charged, CAN vaporize a nice divot in the screwdriver and render the cap's terminal a useless stub. If you suspect the cap might have a charge, use a screwdriver you can afford to lose, and land the blade first, then complete the short with the shaft: the arc will spring from the terminal to the shaft and you'll still have a usable blade end on the screwdriver. As others have said, most caps will be fully discharged through the compressor within a few minutes of shut-down. I short them all because I'd rather replace a yard sale screwdriver for a buck than my fieldpiece meter.

    Caps encountered in residential HP equipment I'm used to aren't big enough to do much damage UNLESS you forget to pull the disconnect! An energized system can yield: 1) welded/blown equipment; 2) a screwdriver converted to a lethal missile; 3) a scorched spot on the earth where your boots where when you smoked yourself.

    I've been to more than one funeral for guys who KNEW the circuit wasn't energized.

  4. #30
    Join Date
    Dec 2011
    Location
    Chandler
    Posts
    16
    what kinda cap are you trying to discharge is the right question...if its a run cap under 80mfds

    it will discharge withing 30seconds MAX

    now a car audio cap..thats a different story....or a cap bank for a diesel power back up...totally different story

    instructors at trade schools tell new techs all sorts of crazy stuff

    i had a new hire tell me i was ruining package units becuse i used a drill to take of panel screws...lmao

  5. #31
    Join Date
    Jan 2011
    Location
    IOWA
    Posts
    11
    I use any tool with rubber handle to verify discharge of run or start caps . Get into habit just because the disconnect looks off doesnt mean all legs are dead bad disconnects will kill .

  6. #32
    Join Date
    Dec 2011
    Location
    Ozarks of Missouri
    Posts
    32

    VERY good point!!!

    Quote Originally Posted by broc123 View Post
    I use any tool with rubber handle to verify discharge of run or start caps . Get into habit just because the disconnect looks off doesnt mean all legs are dead bad disconnects will kill .
    I will ALWAYS check the high voltage side of the contactor, either with the NCV on my meter or if I'm really paranoid, with the leads and that's BOTH legs of the supply wiring.

    You've got the service panel off: why NOT check it: the life you save may be your own!

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