GFCI and ELCI breakers can be confounding, but heed their warning

Ben Stein

Ben Stein

Publisher of, passionate marine electronics enthusiast, completed the Great Loop in 2017.

17 Responses

  1. Mr. Stein, thanks very much for a clear and compelling explanation of this important safety technology. As both a sailor and President of Underwriters Laboratories I applaud your efforts in helping to spread the word about marine electronics safety. We added ELCIs to our own boat and are very glad we did.

  2. Good information, but incorrect about how a GFCI works. You state “These breakers look for current flowing on the grounding conductor of the circuit and trip if current exceeds a threshold ”

    The grounding conductor has nothing to do with the operation of the GFCI. A coil around the hot and neutral wires detects any imbalance between the two and trips the device.

    You can install a GFCI on an ungrounded circuit and it works fine.

    BTW, really enjoy Panbo. It’s one of my favorites.

    • Ben Stein Ben Stein says:

      Mark is absolutely correct. In my research for this article I misunderstood the means of detection for GFCI. I believe that’s been corrected in the article and noted. But, I really appreciate the correction.

      Ben S.

  3. Jim Wood says:

    Can you please explain to the uneducated how installing the breaker isolated the inverter output from the A/C panel.
    If the breaker is on (closed circuit) the current will flow to the panel as if the breaker wasn’t there?? Do the owners have to trip that breaker (open circuit) manually prior to plugging in shore power? My wife and I are friends of these boat owners and were following with interest. We all appreciate that you were able to help them resolve this issue.

    • Ben Stein Ben Stein says:


      You’ve hit the nail on the head and I should have been clearer about the fix. The breaker allows isolating the inverter from the AC panel by turning off the breaker. It’s likely that will only be required in a relatively small number of cases (when an ELCI breaker is encountered) so while it might be inconvenient it shouldn’t be frequently required.

      The longer-term fix likely involves separating the output side of the inverter from the main panel.

      Ben S.

      • Jim says:

        Thank you Ben. This assumes a stand alone inverter? How would this be different if it were a inverter/charger? Would you still be able to isolate the inverter output to the a/c panel without interfering with the charging operation. Appreciate the response.

        • Ben Stein Ben Stein says:

          The breaker is only controlling the AC output of the inverter. So, the inverter is still getting AC power and still connected to the batteries. This means it will still be able to charge the batteries.

          Ben S.

  4. Dave says:

    RCD ( residual current devices. ) have been common in Europe for decades now and are routine in marinas and on boats. Any onboard AC generation must be isolated from any incoming shore supply system , either by (a) seperated unconnected systems (b) manual switch over systems that disconnect all three wires or similar automatic solutions that detect invertor /generator power up. It’s easy to do

  5. Colin A says:

    If I think I get your description right, was the inverter output tied to the entire Bus behind the panel? If so that’s was and still is very problematic. The model of inverter might be helpful for schematic reasons. But let’s say as a worst case the inverter output is wired to the entire bus on that panel and one of say the outlet breakers is feeding the inverter/charger input. For one you have created an interesting loop in the circuit if the inverter has a pass thru relay. But the bigger issue is potentially having the inverter and shore power trying to feed the panel if someone were to shut off the AC feed to the inverter (again assuming a pass thru) Unless the inverter is a synchronizing (and even if it is I doubt this would work correctly) type there is some potential for serious issues as the two AC sources would not be likley to sync.

    Take a look at Victron or Magnum wiring diagrams to see the potential issues on not either having a dedicated inverter section a entire panel pass thru or interlock in place.

    I have seen a whole lot of bad inverter installs over the years. It seems to be one of the most commonly misunderstood type of installs. I have even seen pro’s get tripped up on really complex systems.

    • Ben Stein Ben Stein says:

      You do understand the description correctly and I share your concern about the wiring configuration. Because I didn’t disassemble all of the wiring it’s possible the point of connection for the inverter is further upstream, perhaps it’s connected to the input of the shore power, not on the main panel, but regardless the danger of multiple AC sources is present. It’s because of that danger that I’ve suggested a competent marine electrician be consulted to suggest a remedy to the current configuration. In the meantime the breaker on the output side at least allows for the isolation of the inverter output.

  6. Max Parker says:

    Ben, this is a good explanation. One thing I might add is that as marinas update their dock wiring and have to be compliant with the NEC code, we’ve found some are misinterpreting the rule and are installing 5-mA ELCIs instead of 30-mA ELCIs. Apparently, you can buy 5s at big box stores and 30s have been harder to locate. We’ve found that it is possible to find all the leaks and get boats below 5-mAs of leaks, but it can be a challenge. Bad inverter installations are the biggest culprits followed by neutral to ground connections in home-style appliances (like washer/dryers), bad shore power wiring, and the occasional failed water heater element.

  7. Dave mccabe says:

    Given the likelihood that many AC Devices will have EMI filters which in effect feed small currents into the earth lead ,my experience is getting the overall leakage under 10mA can be quite a challenge . For this reason in Europe , whole house RCBOs are rated at 30mA and are very widely available and cheap ( 10-20 euros ) with a standardised set of characteristics type B C D , which are to do with inrush ( as an rcbo is also a breaker )

    Less then 30mA RCBOs are very specialised and hard to source , and are mainly used in things like outdoor extension cables and the like

    In my marina there are now 5 RCBOs between my boats outlets and the incoming marina supply , making it an “ amusing “ activity tracking down which has tripped , as the discrimination in RCBOs isn’t granular enough to cope with this many and most electrical installs don’t bother sorting out discrimination anyway

    • Colin A says:

      In the US most electrical ELCI/RCBO are placed in the branch circuits or at the plug hence the 5ma trip settings. As you mention many European installations look at it differently. That’s one of the reasons the ELCI rule caused some headaches in the US. GFCI (5ma) are common (30ma) were used mostly in specialty industrial wiring (from what I understand) until the ELCI rule came out.

  8. Alden B Cole says:

    Excellent article and excellent contributions from commentators. One thing I have seen frequently with inverter installations is that the output neutral is connected to the common neutral of the panel. The output neutral of the inverter must have it’s own neutral bus that serves inverter loads. When in pass through mode the neutrals a connected together by a relay. When in invert mode, a relay parallels the ground to the neutral. The grounding conductor(green wire) is NEVER to be interrupted by any sort of switch. Side note: A galvanic isolator is not a switch device, it is a pass through device.

    Also. ABYC techs and other electro techs out there, Sign up for the 45 hour NEC course. These are given 100’s of times a year all over the country and on line too. Google Mike Holt. The courses are low cost and often free. Contact your electrician or state agency for info. Electricians take protection of life and property as their sacred mission. The National Electrical Code is their Bible.

    • Colin A says:

      Have to agree with Alden above. The neutral causes alot of confusion for installers. It also sometimes leads to some odd installations, that may be done right but look strange. If your doing an install I recommend clear labeling, to avoid future issues.

  9. Alden B Cole says:

    I meant 100s of times a year.

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