Hi Tom,
Everything that I have read that tries to put the ABYC specs in layman's terms considers the engine negative terminal as connected to seawater ground, here's one that came up quickly: "The key factor here is that the yacht's electrical system is connected to seawater ground at one point only, via the engine negative terminal or its bus." (The West Advisor)
http://www.westmarine.com/webapp/wcs/stores/servlet/WestAdvisorView?langId=-1&storeId=11151&catalogId=10001&page=Marine-Grounding-Systems
I seem to remember something like that in N. Calder's book too, but I don't have that in front of me right now.
"... allowed, but not required..." that's a great term to include in this type of publication.
I know that they prefer that their documents leave little room for personal interpretation, but this might be one of those spots. I guess that many people consider the engine negative terminal as grounded, but apparently that doesn't have to be the case. (scratching my head too)
That said, for electric drives, one must not connect the DC system negative to the motor's negative terminal, though we are supposed to ground the non-current carrying items like the motor case....
Bottom line, I figure that my system is good enough and as safe or safer than most, that's got to be worth something.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Tom" <boat_works@...> wrote:
>
> Hi Eric,
> My understanding is that ABYC requires the DC system negative to be connected to the engine negative terminal (or its bus) E-11.5.4.7.2, it allows, but does not require, the DC system negative connection to be grounded. E-11 11.5.4.7.4
>
> No, I can't explain it. Any thoughts?
> -Tom
>
>
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