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  1. #1

    Confused New compressor blowing fuses

    I just replaced a 10 ton scroll compressor on a 20 ton system. before I installed the new compressor I flused the coils with CF-20. I used 4 nitrogen tank to blow out the residual CF-20. installed new filter drier. placed system on a vacuum for 1 days because I was unsure as to how much CF-20 was left in the system.I go to the job today to remove vacuum ( I did get the vacuum down to 500 microns ) I noticed that T3 leg on the compressor has been hot as it is wired direct to the incoming power lug. I also notice that the L3 leg of power has a blown fuse. Also the oil sight glass is full. I check for grounded compressor and find no ground. Im wondering if that Cf-20 has filled the compressor and is causing a short. How can I have a short in a compressor that has never run?

  2. #2
    Join Date
    May 2011
    Location
    Raleigh North Carolina
    Posts
    1
    Blowing the nrp cf- 20 out of the system with 4 tanks of nitrogen should have done the trick. The overheated t-3 on the compressor could be from a loose connection. Was the fuses checked before starting the new compressor? Does the compressor have a crankcase heater and is it operational? The clear site glass is either empty or full, the compressor could be full of refrigerant. Not finding a ground in the compressor I would change the fuse and try to start the compressor after checking that overheated connection. Did you weigh in th charge? Who is the manufacture of the equipment?

  3. #3
    Join Date
    Feb 2006
    Location
    Atlanta,GA.
    Posts
    926
    why did you apply power while unit was in vacuum? that is not a good idea.electricity can go to ground arcing in compressor with no refigerant to act as insulator.

  4. #4
    Join Date
    Mar 2009
    Location
    central illinois
    Posts
    532
    somebody turned it on.
    work to live not live to work.

  5. #5
    Join Date
    Jun 2010
    Location
    U.A. (upper Alabama)
    Posts
    873
    Did you meg the comp. or ohm it. Chase1 has a good point about the crankcase heaters. If comp. is filled with liquid refrigerant (or) too much oil, it could be grounding it enough to blow a fuse. I am not familiar with the CF-20 you flushed it with, but if it's like the RX-11 and you pulled it down to 500 mic. it should be sufficient. Did you charge it with liquid? If so, where? Or as stated you had power on the comp. while pulling vac. and you had a lightening storm on the inside.

  6. #6
    Join Date
    Jan 2010
    Posts
    6,784
    [QUOTE=isp tech;10209022]I go to the job today to remove vacuum ( I did get the vacuum down to 500 microns ) I noticed that T3 leg on the compressor has been hot as it is wired direct to the incoming power lug.

    So your saying you wired the compressor up while it was still live on one lag ?

  7. #7
    I screwed up! After thinking about this Ive realized that applying power to t3 while in a vacuum is the same as megging it while in a vacuum. I should have noticed that t3 was wired direct and powered. I f#$&ed up!!! Time to replace the compressor. Stupid.

  8. #8
    Join Date
    Mar 2010
    Posts
    32
    wow. suprised breaker @ panel or mcc didn't trip instead of blow fuse. why was x/o closed at unit? were you trying to keep fan running or keep courtesy plug energized, to run vacuum pump? never apply power or meg a compressor when it's in a vacuum. as far as full sightglass i'm guessing oil equilization line between compressors. anyways can't go back now so put some gas in and see what happends.

  9. #9
    Join Date
    Mar 2010
    Posts
    32
    sorry hit enter to soon. if as you stated compressors dosn't show grounded. put some gas in unit and see what happends damage has been done.

  10. #10
    Join Date
    Dec 2009
    Location
    northeast pa
    Posts
    118
    Quote Originally Posted by isp tech View Post
    I screwed up! After thinking about this Ive realized that applying power to t3 while in a vacuum is the same as megging it while in a vacuum. I should have noticed that t3 was wired direct and powered. I f#$&ed up!!! Time to replace the compressor. Stupid.
    maybe the fuse was blown the whole time.What was wrong with old compressor?Only thing you can do is try running it worst thing that can happen is you have to replace it anyway.

  11. #11
    I would put gas in it except for the fact that when this compressor is wired it blows the fuse even when its not running. I left the power on to keep stage 1 running. I disconnected the 24v to stage 2 compressor contactor thinking that would be the right thing to do. I dont think it will run?

  12. #12
    Join Date
    Dec 2009
    Location
    northeast pa
    Posts
    118
    Quote Originally Posted by isp tech View Post
    I would put gas in it except for the fact that when this compressor is wired it blows the fuse even when its not running. I left the power on to keep stage 1 running. I disconnected the 24v to stage 2 compressor contactor thinking that would be the right thing to do. I dont think it will run?
    is L3 wired direct to main lug did it blow the before the replacement?

  13. #13
    Join Date
    Jan 2005
    Location
    Houston TX
    Posts
    880

    Check it first

    ISPTech: You NEVER apply power to a compressor when it is in a deep vacuum. As Chillerout1 has already stated. What has happened is the voltage from the T-3 leg has broken down the compressor windings and went to ground. If this is a 460 volt unit, you have applied 277 volts to those winding with about 100 amps from the main fuse until it blew. I would first disconnect all the power legs to the compressor and meg the compressor at 500 volts (megger voltage) with about 10#s nitrogen pressure in this compressor, don't take just standard ohm meter readings. I think you are right ISPTech in that you are going to be changing another compressor out. Experience is a very costly teacher in this case. Good luck and be safe, as the only thing that helped you was that L-3 fuse was open while you were disconnecting the T-3 leg.-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

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