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  1. #1
    Join Date
    Apr 2012
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    Louisiana
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    Rental Chiller Amps to Ground.

    I was reading another post about bonding and current to ground being insufficient to trip the overfault saftey and didn't want to hijack it.

    Several years ago, I put my meter on the ground conductor of a rental chiller. I read 60 amps to ground, I brought this up with my company and the rental company. Checks indicated no grounded motors or compressors.

    Since then, I have used two other rental chillers with the same configuration and they both read about the same amps to ground.

    All were 208v main panels supplying a step up transformer and a 460v rtaa chiller. The transformer and chiller were both on the same flatbed trailer. Only four conductors were ran all three times, 3 lines and a ground. I'm fairly certain it was not the same chiller each time.

    Does this have something to do with the step up transformer. Is it normal? I was concerned each time, rental company acted like it was normal but did not explain it.

  2. #2
    Join Date
    Jul 2000
    Location
    Dallas,Texas
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    I just ran across this. I think I can tell you what is going on if you are still interested.

  3. #3
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    Apr 2012
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    Louisiana
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    Thread Starter
    I'm all ears.

  4. #4
    Join Date
    Apr 2012
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    Louisiana
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    Thread Starter
    I've got a rental on a job right now.
    460v cgam rental chiller.
    208v service.
    rental came with a step up tranformer
    approx 100 amps on all three legs measured at the site service panel.
    22-27 amps on the ground wire at the site service panel

  5. #5
    Join Date
    Jul 2000
    Location
    Dallas,Texas
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    Sorry, I need to check things a little more often.
    Your transformer is misapplied and\or wired incorrectly.
    For what you are describing, the neutral should not be connected. It is a derived neutral from the WYE windings for the purpose of 120 volts. Your application is using 208 wye to step up to 460 delta. You don't need a neutral on either side of the transformer. The chiller picks up it's control voltages from 460 x 240 transformers and 240 x 120 and 24 volt transformers.

    The neutral on the supply side being bonded to ground violates the NEC in several places and probably is doing some weird stuff in the supply system.
    The transformer would need to be grounded to the cabinet but the neutral should not be bonded and any voltage measurements from load to the neutral on the line side will be spurious and unreliable.

    If that doesn't make sense, let me know and I can give you the long version.

  6. #6
    Join Date
    Apr 2012
    Location
    Louisiana
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    Thread Starter
    thanks

    Sent from my SCH-I545 using Tapatalk

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