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  1. #14
    Join Date
    Mar 2012
    Location
    Birmingham Al
    Posts
    266
    someone will tell me i am wrong for this, i will wire those 2 contactors together every chance i get. This can cause a "voltage drop" on the entire building when the compressor starts, dimming the lights. if it is an industrial plant or another commercial building with a large power draw i have never had a complaint from doing this. the entire purpose of part winding start from my understanding is to limit the inrush current. I may be wrong about this.

  2. #15
    Join Date
    Mar 2012
    Location
    Birmingham Al
    Posts
    266
    also, on most breakers i find inside of the unit are rated for slightly more than the rla of the unit, lra of the unit are normally 3 or 4 times more than rla. i would be surprised at those amp draws if the compressor was locked and something else wasn't the problem. on the other hand it may be tripping before it reaches is true lra.

  3. #16
    Join Date
    Aug 2012
    Location
    willowick ,oh
    Posts
    261
    the 2 additional wires are probably an aux switch for sump heaters or an internal overload to trip the breaker on an internal issue in the compressor. need the schematic to tell. Oh well tho off to the scrap yard for that old gem. I would stray away from any wiring that differs from the factory setup. IMHO if you believe that wiring equipment a different way from the design is better, run it by carrier tech support to find out why you shouldnt first.

  4. #17
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    Even though it's going to the scrap pile, we can still learn from it. Where were the two wires you were talking about at? Auxiliary contacts on the contactor or in the peckerhead of the compressor? If its under the peckerhead, I'd say they are winding sensors.

  5. #18
    Join Date
    May 2004
    Location
    Salt Lake City/Tooele
    Posts
    2,592
    Model number of the compressor doesn't show that it has part-start windings. Those large tonnage split system condensers are notorious for high head issues that lead to compressor failure due to the fact that no one is splitting the stacked coils and cleaning between them. The Carrier 38AK units are also susceptible to low oil return if they are not piped properly to the remote air-handler or coil box(s).
    You would know if this was a part start compressor, based on two main contactors that would feed SIX large wires to the compressor. Part start compressor are used in low voltage situations. The first contactor would close and give the compressor an initial bump and within a split second the other contactor would energize to complete the start-up of the compressor. Very obvious though if it was a part start.

    I know the company is not interested in fixing, but at least the remaining units can be properly serviced. Make sure that the oil is no less than about a 1/4 of the site glass, clean the stacked coils. Make sure crank case heaters are operating. Make sure the remote evaporative coils on the working units are clean and filters replaced regularly, with registers, grilles, etc open and unobstructed.

    Keeping up with this should get the remaining systems through this summer.

  6. #19
    Join Date
    Jul 2007
    Location
    The Hot South
    Posts
    1,346
    Quote Originally Posted by Birmingham View Post
    someone will tell me i am wrong for this, i will wire those 2 contactors together every chance i get. This can cause a "voltage drop" on the entire building when the compressor starts, dimming the lights. if it is an industrial plant or another commercial building with a large power draw i have never had a complaint from doing this. the entire purpose of part winding start from my understanding is to limit the inrush current. I may be wrong about this.
    You are wrong on this. You have it backwards. Wiring the 2 contractors together makes it across the line start which is what dims the lights and causes the voltage drop. That defeats the purpose and extra cost of part winding start.

  7. #20
    Join Date
    Feb 2004
    Location
    Brooksville, FL
    Posts
    27
    I haven't had opportunity to get back into this unit. Not sure when I will. There are 8 wires connected to the compressor via 5 terminals. Both contactors are wired to the same 3 terminals and there are 2 additional wires which I did not trace to determine purpose.

  8. #21
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    Quote Originally Posted by thelmuth View Post
    I haven't had opportunity to get back into this unit. Not sure when I will. There are 8 wires connected to the compressor via 5 terminals. Both contactors are wired to the same 3 terminals and there are 2 additional wires which I did not trace to determine purpose.
    When you do, take some pictures so you can turn this into a learning experience.

  9. #22
    Join Date
    Feb 2004
    Location
    Brooksville, FL
    Posts
    27
    Finally had some time to get back to this one yesterday. The powers that be now want to fix this because it also cools the production office and they have been requesting "an extra A/C vent" because it's warm in there. I went above the grid and saw that the 2 drops they have are coming from this dead unit. Interesting how things change depending on who is affected.

    Switched two wires around to try starting it backwards hoping to break it free. No good. So now we are in the process of pricing a compressor.

  10. #23
    Join Date
    Feb 2004
    Location
    Brooksville, FL
    Posts
    27
    Quote Originally Posted by ryan1088 View Post
    When you do, take some pictures so you can turn this into a learning experience.
    Spent a few minutes following wires and looking at the diagram. The extra two terminals go to an internal protector, wired in series with the high and low pressure switches. The bottom 2 blue wires are the ones I'm talking about.

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  11. #24
    Join Date
    Oct 2005
    Location
    B.C. Canada
    Posts
    903
    Not part winding start...time for a new compressor

  12. #25
    Join Date
    Apr 2010
    Posts
    94
    This brings back nightmares for me. I had this one location that lost this compressor nearly every year. Luckily the customer got tired of this clunker and swapped out the unit.

  13. #26
    Join Date
    Feb 2004
    Location
    Brooksville, FL
    Posts
    27
    New compressor being installed tomorrow. He spec'd it to be replaced with a copeland scroll. It will be interesting to see his plumbing job on that.

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