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Current flow

Walk up to a roof top unit today with the stat in off mode the condenser motor was slowly turning.The compressor was couching like it just had a cigg.Also a nice little arc at the disconnect box where the screw for the conduit cover plate was.Buzzzzzzzzzzzz!

240 volt 60 amps circuit single phase with ground.Contactor was one pole.

What did I find?


  • Ken D.
    Ken D. Member Posts: 836

    Sounds like a grounded winding somewhere. Maybe in the fan or comp. Could have lost a leg and one side is grounded.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    We're Waiting

    C'mon Don... what did you find?
  • don_185
    don_185 Member Posts: 312

    just what I was thinking as well Ken.However,I had 240 volts
    at the disconnect box and what puzzle me was the amp reading I was getting on one leg and nothing on the other.

    So I pulled all the wires off all the loads and started checking them to ground.All checkout ok.Then it hit me...
    that one pole contactor.Whats its called trickle volts is that the correct term?

    I started checking the wires coming from the contactor snipping wire ties as we go.I work my way down the commom wire to the compressor.I find the wire is pinch between the
    compressor and the lines coming off the reversing valve.
    The wire has been cut thru from the edge of the compressor
    dome and is grounded to the compressor and copper lines of the reversing valve.

    Repair the wire..started and cycle the system all is well.

    I also install the correct fuses and maybe if it happen again she will blow the fuses this time.

  • mtfallsmikey
    mtfallsmikey Member Posts: 765
    Thought about something similar

    Had problems with a Traulsen commercial fridge at my old job. only 90 volts to the lower compartment freezer fan, turned out internal wiring (stranded copper)was corroded,acted like resistance wire. Factory said it was a "small" problem in some of their units.
  • Ken D.
    Ken D. Member Posts: 836

    Bingo, It's nice when you find something like that. Nice job.
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