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Ground Fault Victory!

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    Ground Fault Victory!

    Last summer we ran into issues with plugging our 1988 3818 into shore power. In each case the marina had “upgraded” the ground fault system to the new ABYC regulations which lowered the allowable ground fault from 100ma for x duration to 30ma for less than x duration. It took a while to work out with an excellent Marine Electrician, largely because of my schedule and wanting to do the necessary modifications myself, then there were the two surgeries that slowed things down.
    I made a ground fault tester using one that intended for contractors and blows at 2ma and 30 amp connectors. The knee jerk reaction from lots of people was that it had to do with the inverter and the time it takes for it to process that there is 120v power inputting. In the “unplugged” condition the unit is in a grounded condition, when power is input, the ground is opened. However, that takes a few milliseconds.
    The way my inverter was installed by a previous owner, the load (hot, black wire) bus was cut to form a sub panel of breakers. This sub panel has a “master” switch to activate breakers for the fwd & aft outlets, microwave and refrigerator. There was an “input” load wire going to the inverter, neutral connected to the neutral bus, ground to the ground bus. On the “output” side, the load wire goes to the “inverter master”, the neutral goes to the neutral bus and the ground to the ground bus. To make sure I had the correct neutral matched with the load I started by disconnecting all of the neutral wires and removed the factory bus. Then, starting with each load wire at the breaker, followed it back to the sheath, took the neutral and followed it to the connector and labeled it. Repeat, repeat, repeatedly.
    The issue with ground fault was solved by breaking the neutral bus into three. One bus for line one on the breaker panel, a second for line two on the breaker panel then a third bus for the inverter circuits. I can now plug my test gfi into either line or the splitter and not have an issue.
    There are going to be a bunch of us with this problem as marinas change to the new regulation. Hopefully you can use my solution as a guide and save you a bunch of frustration.
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    MMSI 367770440

    #2
    That was a tricky one. I will keep this in mind. Apparently there is a small voltage potential between the inverter neutral and the house neutrals?
    '89 3888
    "RUM AWAY"

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      #3
      Great post, Thanks!

      I ran into that problem when they plugged my boat into shore power while on the hard. It’s been on the list but I hadn’t taken the time to figure it out yet.

      It does male sense. When in “invert mode” the inverter becomes the “service entrance” which is the point where the neutral is bonded to the ground. When in pass through mode the “service entrance” is in the shore power ped on the dock.


      KEVIN SANDERS
      4788 LISAS WAY - SEWARD ALASKA
      www.transferswitch4less.com

      Whats the weather like on our boat
      https://www.weatherlink.com/embeddab...59665f4e4/wide


      Where are we right now? https://maps.findmespot.com/s/36S4

      Comment


        #4
        Part of the challenge is thinking that neutral = neutral anytime. When most people install inverters they connect the neutral supplying the inverter to the same bus as the neutral coming back from the inverter. In fact, whoever installed my inverter didn’t connect the neutral or ground to the inverter, just connected the out and in wires together. I discovered that when I was trying to figure out why it wasn’t working correctly when I bought the boat. That part turned out to be a bad circuit board in the inverter. The first time I ran into this was at Roche Harbor when we were put on a dock with rather new, rather large, rather over the top yachts. The staff, who are like being at a five star hotel, commented that almost every boat on that dock, the first to be upgraded, had problems plugging in immediately but they didn’t have any idea of why.....something about the inverter.
        The separating the neutrals coming from the inverter, it puts the inverter on what is effectively it’s own subpanel, which if you look at the installation instructions carefully enough, you’ll see.
        It’s no problem with outlets that are not updated to the new ABYC regulation because the size and duration of the ground fault switching within the inverter, even though both neutrals are connected to the same bus, is small and short enough not to trip the breaker. Enter the new regulation and that doesn’t work anymore.
        I overkilled the test inline gfi by installing the 30 amp plugs. I did that so I could reset it at the boat rather than at the power source as I plug in using a 15 amp plug.
        I really have to thank a very unusual Marine Electrician, Matt Netting, who was interested in finding a smoking gun and fix to share with other Marine Electricians as well as capable do it yourselfers. I highly recommend his services.
        I’m by no means an expert on any of this. I just had too much time on my hands to learn about it. I had a very successful back surgery August 1st, then my gal bladder taken out Labor Day leading to lots of armchair cruising and maintenance.
        P/C Pete
        Edmonds Yacht Club (Commodore 1993)
        1988 3818 "GLAUBEN”
        Hino EH700 175 Onan MDKD Genset
        MMSI 367770440

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