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  1. #1

    Copelematic compressor repair?

    Hi folks,

    I'm not sure if this would be in the right discussion area so I wont be suprised if it gets bumped.
    I'm a millwork and cabinet shop owner that recently scrounged a Copelametic model # KAT4-0100 dental compressor off a job that was going to the dumpster.
    Brought it to my maintenance corner in my home's basement and cleaned it up, drained the oil refilling with straight grade 30w, plugged it in and it fired right up! Love at first fire! SOoooooo quiet, so perfect for my basement needs. Ran fine for several charges but then it started to blow the circuit breaker. It's plugged to a 20 amp circuit 10' from the panel.
    Started my investigation and checked for any loose connections. Nothing there so I checked the motors field windings for resistance. The run winding wire lead and common lead showed 1.7 ohms and the start winding lead and common lead showed 3.9. Tried probing the run and start leads next and still got 3.9... Odd.
    I next tried to see if there was any ground fault in the windings by checking for continuity of either winding and a bare spot on motor housing acting as ground. Nothing there. No beeps from volt ohm meter's continuity tester.
    I still have another coupla doo das to check in the circuit but my questions are these:
    Would anyone having experience with these compressors in the fridgeration world know if those Ohm readings are in the normal range?
    If the reads are out of spec, are these motors re-buildable?
    I own both new and old milling equipment and have used quit a bit over the years. I must say that this compressor has impressed me with its build quality and operation. I'll go the extra to keep something going but there may be a point of diminishing returns for some things getting repaired. Don't know much about these compressors so I don't know what the conventional wisdom is about repairing them. Any insight would be a great help.
    Thanks again.

  2. #2
    Join Date
    Jun 2014
    Dover, DE
    What are you trying to pump with the compressor? What voltage is it rated for? Is there starting components hooked up to it?

  3. #3
    Hi Rider,
    The pump is single phase 120v. I'd like to be able to use it for light bench use. Nothing heavy or continuous. The occasional brad nail or dusting off.

  4. #4
    Whoops! Forget to answer that it has a pressure switch and thermal switch in the circuit. It trips the breaker after about 5 seconds from start up, starting up with 0 psi. No unusual noises coming from the compressor or motor. No bad bearing sounds. Havnt pulled the bell ends and inspected the internal conditions but it does put out a strong supply of air in the brief run time befor tripping the breaker.

  5. #5
    Join Date
    Aug 2009
    Does it have a wiring diagram? Check for a capacitor in the diagram.

  6. #6
    Join Date
    Sep 2005
    Atlanta GA area
    Not sure of the application it 'was' in... however it may need some 'back pressure' to work properly.

    As noted above, look at the start components.

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  7. #7
    Join Date
    Oct 2012
    I've heard those are great air compressors.

    Generally the sum of adding the resistance of start to common plus run to common will equal run to start.

    If your meter readings are accurate, it would point to a problem with the motor. Did you have the wires disconnected from the terminals when you checked with the meter? If the wires where connected you could be reading the resistance of something else in the circuit.

  8. #8
    Join Date
    Mar 2010
    Sunny SoCal
    Quote Originally Posted by ga-hvac-tech View Post
    Not sure of the application it 'was' in...
    I googled the mod# and come up with this......

    Apparently Copeland also makes or at least made compressors to be used as air compressors.

    In the EBay example the voltage is 230v 1ph 5.0amps so your 115v should pull 10amps. (All things being equal).
    Make sure your circuit breaker is in good shape and if possible switch breakers (& don't kill yourself in the process plz).

  9. #9
    There are two caps. One rated for 40uf and the other 430-516uf.
    The wires were disconnected from terminals. I tried a couple of times and got the same result. The start and run terminals were the same as the start and common terminal. Odd.
    I'll check the caps but If it is the motor that'll be unfortunate.

  10. #10
    Join Date
    Oct 2012
    On a refrigeration compressor, if the motor fails you replace the whole compressor.

    I'm not sure if they sell motors for the dental compressors or if you just replace the whole compressor too.

  11. #11
    That's a shame. Its a one peice cast iron construction with the compressor head and motor body all in the same casting. A very robust peice of construction. The older I get the more tired I get of disposable design but the cost of repair might trump that sentiment. I havnt had the need to use a motor rewind/repair shop in over a decade (are there any out there still?) but I'll start poking around to see. It might throw a shop to GDR a compressor attached!
    This unit looks like it could have been built 80 yrs. ago.

  12. #12
    That is a dual head from my understanding. Mines a single. Looks like maintenance had a slow week and decided to paint the equipment for that unit. Yikes!
    I've tried another outlet with the same result. Tripped breaker.
    Ill say it again, it had to be one of the smoothest and quietest compressors I've observed. On the other hand, I'm usually surrounded by conventional nail gun compressors like my older emglow twin tank.
    If the caps check out i suppose I'll have to see if rebuilding is realistic.

  13. #13
    Join Date
    Oct 2012
    Those are still widely in use in refrigeration, but you see them less and less in new equipment.

    And I should clarify, with these semi-hermetic compressors, we get remanufactured compressors, and give the old one back to be salvaged and remanufactured.

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