Results 1 to 8 of 8

Thread: Ground Fault?

  1. #1
    Join Date
    Mar 2016
    Location
    Washington State
    Posts
    60

    Ground Fault?

    Hello,

    So we are installing an Outback Radian as a grid tied with battery system along with Outback Rapid Shutdown System.

    One of the components of the rapid shutdown is a ground fault detection interrupter breaker, that gets connected to all sorts of sensors.

    So I go to turn on the PV and the breaker immediately trips. I check wiring, everything looks good as far as I can tell.

    I call Outback Tech. We go through all the wiring of the system, seems good. He sends me up onto the roof and has me check voltages.

    I see 70.3 volts between PV+ and PV-, 0 volts between PV- and ground, and 67.2 between PV+ and ground.

    He tells me this is my problem, I have a short somewhere. So I check each string, 5 of them. Every string shows very similar if not identical voltage readings, meaning every string has a short. At that point I say no way. The likely hood of this is too small and on top of that I wired it all myself, and it was done cleanly.

    At this point I had to leave so couldn't do a lot more.

    Any ideas? Anymore tests I could do to see where the problem may be? My gut tells me its still a mis wiring issue in the equipment somewhere or a bad breaker. But the tech was convinced it was a short at the array.

    thanks for any suggestion

  2. #2
    Join Date
    May 2011
    Posts
    4,122
    Isn't the Radian a negatively grounded system? If so you should see the same voltage between positive and ground as you see between negative and ground, when everything is hooked up. But the fact that you see a few volts difference does seem to corroborate a ground fault problem.

    Ir order to identity the location of the fault you have to disconnect both positive and negative on any string as you test it to ground, or else you'll also be partly measuring the voltage to ground through the other strings, and not get accurate measurements of either.

  3. #3
    Join Date
    Aug 2016
    Location
    Texas
    Posts
    40
    When you turn on the inverter, the GFDI breaker trips off which means the negative is not grounded anymore. But you said you still read 0 volts between negative and ground, I suspect you have a bad negative PV wire somewhere in your system.

  4. #4
    Join Date
    Dec 2012
    Location
    Placerville, CA, USA
    Posts
    19,130
    Quote Originally Posted by hill900505 View Post
    When you turn on the inverter, the GFDI breaker trips off which means the negative is not grounded anymore. But you said you still read 0 volts between negative and ground, I suspect you have a bad negative PV wire somewhere in your system.
    Or, equally likely, you have inadvertently made a bond between the common string negative bus and ground. This could also be fault in any one of the panels at the negative end of a string. A pinched wire is another possible source of the problem that hill indicated.

  5. #5
    Join Date
    Oct 2009
    Location
    Austin, TX, USA
    Posts
    9,277
    Quote Originally Posted by jaggedben View Post
    Isn't the Radian a negatively grounded system? If so you should see the same voltage between positive and ground as you see between negative and ground...
    Don't you mean that the positive to negative and positive to ground voltages should be the same? I agree that a small difference implies a high resistance ground fault somewhere other than in the negative home run. A pinched wire, maybe?

  6. #6
    Join Date
    May 2011
    Posts
    4,122
    Quote Originally Posted by ggunn View Post
    Don't you mean that the positive to negative and positive to ground voltages should be the same? I agree that a small difference implies a high resistance ground fault somewhere other than in the negative home run. A pinched wire, maybe?
    Yes, I mistyped. Thanks, and I agree likely a pinched wire.

  7. #7
    Join Date
    Mar 2016
    Location
    Washington State
    Posts
    60
    Why do I not see voltage between Negative and ground? Shouldn't I find the leaked ~4 VDC here?

  8. #8
    Join Date
    May 2011
    Posts
    4,122
    Quote Originally Posted by bbartmasse r View Post
    Why do I not see voltage between Negative and ground? Shouldn't I find the leaked ~4 VDC here?
    Either because you are testing with the GFDI breaker turned on, which bonds negative to ground directly, or because the fault is on a negative home run as hill90505 suggested.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •