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  1. #1
    Join Date
    Jul 2012
    Location
    North west Arkansas
    Posts
    86

    How to size Cap. when no information available

    Monday morning, went to my bosses rental property, found bad cap, but couldn't read anything on it due to rust, and no information was legible on the compressor either. It looked like a small unit, 1-2 ton split system, 208v. Put 7.5mfd on fan and a 50mfd on comp, system pulled right at 10 amps.
    I understand that if the cap is oversized, it'll cause the comp to overheat, but it hasn't yet..

    My question is, is there a way to figure out what capacitor to use in situations such as this?

    Thank you gentlemen

  2. #2
    Join Date
    Jun 2012
    Location
    Philadelphia, PA
    Posts
    6
    If there is no information available on the machine you can call your local dealer with tghe model number and serial number and they can tell you what capacitor should be on there.

  3. #3
    Join Date
    Feb 2010
    Location
    In a boiler room
    Posts
    7,126
    Could you read the model number on the unit?

    What tonnage was it?

  4. #4
    Join Date
    May 2011
    Location
    Washington, DC
    Posts
    988
    Quote Originally Posted by whitextreme View Post
    If there is no information available on the machine you can call your local dealer with tghe model number and serial number and they can tell you what capacitor should be on there.
    +1
    Ron

  5. #5
    Join Date
    Jun 2007
    Location
    Greenwood Indiana (Indianapolis)
    Posts
    420
    Quote Originally Posted by texasgentleman2 View Post
    Monday morning, went to my bosses rental property, found bad cap, but couldn't read anything on it due to rust, and no information was legible on the compressor either. It looked like a small unit, 1-2 ton split system, 208v. Put 7.5mfd on fan and a 50mfd on comp, system pulled right at 10 amps.
    I understand that if the cap is oversized, it'll cause the comp to overheat, but it hasn't yet..

    My question is, is there a way to figure out what capacitor to use in situations such as this?

    Thank you gentlemen
    sounds like you were guessing on what size capacitor to install. If I was to guess i would of tried a 35+5 capacitor. Seems to be very common on small a/c's. Possibly look at fan motor and it just might say what size capacitor the motor would take.
    As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84

  6. #6
    Join Date
    May 2008
    Location
    Myrtle Creek. Oregon
    Posts
    182
    or even smaller than a 35+5!!
    a stupid question is a question you wont to ask, but don't

  7. #7
    Join Date
    Jul 2012
    Location
    North west Arkansas
    Posts
    86
    Didn't see model, or even a Brand label on the unit. From the size of it, I'd guess 1 maybe 1.5 ton.

  8. #8
    Join Date
    Jul 2012
    Location
    North west Arkansas
    Posts
    86
    Yes Sir, it was pretty much a guess. I hate to do something like that, but it was a size I had available and I thought if it was too far out, the amps would tell me.

  9. #9
    Join Date
    Sep 2003
    Posts
    1,675
    what about the evaporator coil?

    Sometimes you can get lucky there

    Did it have a txv?.....leave no stone unturned...lol

  10. #10
    Join Date
    Jul 2012
    Location
    North west Arkansas
    Posts
    86
    Quote Originally Posted by small change View Post
    what about the evaporator coil?

    Sometimes you can get lucky there

    Did it have a txv?.....leave no stone unturned...lol
    Didn't think about looking there..

  11. #11
    Join Date
    Jul 2012
    Location
    Near Chicago Il.
    Posts
    125
    Last time this happened to me it was after hours & I had no one to call. Could not read the cap or the name on the plate. I got lucky though. I could read the tag on the fan motor to know that side was a 5.
    Then, it came to me after a bit and almost surrendering to taking my best guess. I googled model number on the stamped plate on the top of the compressor and was able to find the cap size that way. It took some digging, and was slow since it was from my phone, but eventually I found it and was able to verify it against a second source, so I felt ok about it.

  12. #12
    Join Date
    Nov 2011
    Location
    Michigan
    Posts
    53
    I'd say you went a little high on the compressor. But as long as it's running ok. I guess your safe. I believe if your under sized the compressor will overheat. If you dig around that compressor long enough you'll find numbers.

  13. #13
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,665
    As long as its the bosses house who cares he can afford a new compressor

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