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  1. #14
    Join Date
    Jun 2006
    Location
    New Jersey
    Posts
    4,330
    Quote Originally Posted by hvaclover View Post
    a megger was designed for a hermetic comp, not an open motor. but I'm sure a megger is misapplied like a lot of instruments.
    Was this statement about meggers in general or just the Supco, mentioned?

    Sent from my C771 using Tapatalk 2

  2. #15
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,789
    say a wire going to a blower motor has a cut in it running thru a package unit. it blows a fuse every once in a while. you can not figure out why the fuse blows. you whip out your extech 380260 meter. you test the blower and it shows up good. you then test each wire that feeds the motor to ground. would the extech 380260 meter pickup the crack in the wire?

  3. #16
    Join Date
    Jan 2008
    Location
    In the work truck
    Posts
    2,990
    Quote Originally Posted by gravity View Post
    say a wire going to a blower motor has a cut in it running thru a package unit. it blows a fuse every once in a while. you can not figure out why the fuse blows. you whip out your extech 380260 meter. you test the blower and it shows up good. you then test each wire that feeds the motor to ground. would the extech 380260 meter pickup the crack in the wire?
    Yes it should. But Id be curious to know if anyone else used a megger in that manner. I think you would be better off doing it the way your doing it. Physically check the wiring and ohm it out...

    I have never condemned a motor that I didnt double check with my Fluke 28 II. I think they are more of a PM tool than anything else. Maybe Im Wrong but from what I read here and from Supco's website thats how I understood it.
    Gotta have the right tool for the job!

    Where is all the stuff MADE IN THE USA?

    "Thats what we do Troy. Incredible, Invisible, Imbelivable things. We are an Unseen, Unknown, Unvincible fraternity of craftsman.."

  4. #17
    Join Date
    Jul 2006
    Location
    NW burbs of Detroit
    Posts
    6,058
    I don't claim to know everything but RSES membership would sure benefit a lot of guys on here.

  5. #18
    Join Date
    Apr 2011
    Location
    Coastal Maine
    Posts
    810
    I tend to agree with HVAClover on this one, although not as stern in my objections. A megaohmmeter is a useful tool with hermetic compressors. It is just that, a tool, among many others. I have used them as a final check before condemning a compressor. Mine is older than most of you guys. I just bought one of the Exetech analogs as my old one is tired of being bounced around in the back of the truck.

    But there is no single tool or meter that will do everything for you.

    In my opinion, stick to the analog meters when reading MegaOhms.

    Good Luck.

  6. #19
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,789
    if you were to use a regular meter while trying to find the crack in the wire that fed the blower motor you wouldn't have found it. this crack in the wire was found using a megohmer. the unit would run fine for a couple months and then blow a fuse. a new fuse would be put in and it would run for a few more months and pop a fuse. i have a supco m500 and it works but sucks at the same time

  7. #20
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    873
    Gravity- Common sense would dictate the answer to your question about a crack in the electrical wiring. Depending on where the crack is located in relation to the pinching action of the cabinet. A Carrier unit was doing exactly that with the condenser fan wires. If you megged the wires you would get a reading that would not indicate a problem. If you isolated the individual fans, there were 4 you would find a grounded lead supply power to the motor. The wire harness was pinched between 2 cabinet top sections and would only show a fault when the rest of the system was in operation.-GEO
    Once in a while everything falls into place and I am able to move forward, most of the time it just falls all over the place and I can't go anywhere-GEO

  8. #21
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    If you are using one as a one time pass/fail test for condemning compressors, you are most likely condemning a lot of perfectly good compressors.

    Quote Originally Posted by hvacrmedic View Post
    The M500 is quite possibly the worst megohmmeter ever made.
    Nah, it is 2nd to the Supco megohm meter it replaced.
    If more government is the answer, then it's a really stupid question.

  9. #22
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    http://fieldpiece.com/megometers/smg5

    mine has served it's purpose through the years I've had it
    It`s better to be silent and thought the fool; than speak and remove all doubt.

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