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  1. #1
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257

    Capacitor voltage?

    Working on a a/c unit(220volt).found a bad run capacitor.The original capacitor is a 35uf-440vac.replaced it with a 35uf-370vac(thats all I could find in-town).will going from a 440 to a 370 vac rating cause any problems?Thanks in advance!
    Artificial Intelligence is no match for Natural Stupidity

  2. #2
    Join Date
    Aug 2008
    Location
    Fremont, Ca
    Posts
    22
    What is the voltage of the system you are working on?

  3. #3
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    220 volts
    Artificial Intelligence is no match for Natural Stupidity

  4. #4
    Join Date
    Aug 2008
    Location
    Fremont, Ca
    Posts
    22
    You'll be just fine!

  5. #5
    Join Date
    Oct 2007
    Location
    Miami, FL.
    Posts
    417
    If the compressor calls for a 35x440 , use a 35x440. You can replace a 370 with a 440 but not the other way around.

  6. #6
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    Thanks for the replies guys.It might be a week till I am able to get the correct capacitor.Is the compressor safe till then?
    Artificial Intelligence is no match for Natural Stupidity

  7. #7
    Join Date
    Sep 2007
    Location
    Yuma, Arizona
    Posts
    252
    The capacitor is unsafe.

    We've all installed a 370 volt in place of a 440 volt run cap but I've never

    done it with intentions of leaving it that way for longer than a day at the

    most. Your compromising not only safety but the equipment also.

    **NOT RECOMMENDED**

  8. #8
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,414
    Tell the supply houses to only carry 440 caps. Much safer bet that way.

    I think there might be some over reacting... as far as a safety issue... beh, it's not going to kill anyone unless someone is sitting there staring at the cap constantly.

    Could it fail prematurely? Absolutely, and it likely will... probably will last several days, maybe several weeks. Hell, might be dead already, tough to tell.

    I'd let it run and go back to replace it with the right cap asap... that's just me though
    "If you call that hard work, a koala’s life would look heroic."

  9. #9
    Join Date
    Feb 2006
    Location
    SouthEastern Virginia
    Posts
    1,075
    I think Skullmonkey has lockjaw.
    It might get loud!

  10. #10
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,024
    Quote Originally Posted by BSJM View Post
    You'll be just fine!
    No.

    The capacitor sees back EMF (Voltage) off the compressor's windings. The start and run act somewhat like a transformer.

    The back EMF will be higher than the 220vac the unit is supplied with.

    Next service call put your meter between the Herm and C and see what you get.
    Beware of advice given by some guy on the Internet.

  11. #11
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    Thanks for the replies.The guy I bought the 35-370 cap from has been in the industrial electric motor rebuilding field for 30 years.He said it wouldn't be a problem.He said it may not last as long.After reading the posts here and other manuals,they all say caps can be repaced with a higher voltage rating but not lower.Also the uf can have a 10 percent difference + or - on the start cap only not the run cap.I ordered the correct cap(should be here tonite)and will replace the lower voltage one.This was an excellent lesson in capacitors for me.
    Artificial Intelligence is no match for Natural Stupidity

  12. #12
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,024
    I only put 440 vac on my truck.
    Beware of advice given by some guy on the Internet.

  13. #13
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    Got the replacement capacitor in today.It is a 35uf with a dual voltage rating of 370/440 vac.
    Artificial Intelligence is no match for Natural Stupidity

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