The question of eliminating the ac-dc ground connection if an ELCI is installed is an interesting one and I'm glad that Paul brought it up. There's no question that isolating the ac green wire ground from the boat's dc ground system will eliminate dc current flowing through the shore power system. The safety issue is the main concern with this isolation and is why ABYC still requires these to be bonded, AFAIK. The ELCI breaker itself will do nothing to prevent stray dc current flowing through the shore power system. I think Paul's point is that it eliminates the shock hazard for nearby swimmers thus allowing the ac ground to be disconnected from the dc ground. I think this is largely true, provided the ELCI is correctly installed and functional and the ground connection is truly eliminated. Most marine surveyors will check for bonding between ac and dc ground, and will note it as an issue if they are isolated - at least while ABYC requires it.
Also, ELCIs are not equivalent to GFCI devices. The principle is the same but GFCI devices operate at 5 mA of leakage while ELCI breakers operate at 30 mA (or 100 mA for some shoreside breakers). While 30 mA is unlikely to be fatal, it can be harmful. 5 mA is generally considered to be safe - although noticeable. The galvanic isolator is a proven device - simple to install and rarely fails. It is essentially the poor man's isolation transformer. I certainly wouldn't consider it a waste of money, especially if the ac and dc grounds are tied together. The ELCI is also a great safety upgrade for older boats but can expose wiring and equipment shortcomings, especially battery chargers and inverters. Marinas that have added ELCI to shore power connections see a lot of tripping when boats connect to shore power. Also important to understand that even complete isolation between shore power ground and boat ground will not eliminate all stray dc current, especially in salt water. Stray dc current can flow from boat to boat due to wiring problems and equipment faults. This can occur even with no shore power connection at all. In our marina, even boats with isolation transformers only get 6 months out of shaft anodes - this varies depending the location of the slip. Cheers, Dave Castor Port Angeles, WA On Mon, Jun 3, 2019 at 3:12 PM Dreuge via CnC-List <[email protected]> wrote: > Joe, > > I think there is some confusion. I’m also guessing that you did not > follow the link and read my more detailed blog discussion. I don’t blame > your reaction, I would have reacted the same way a little while back. > > > I disagree with this. > I have had a galvanic isolator since about 1995 or so. Mercury Marine sold > them to keep their outdrives from dissolving back then and I grabbed one. I > can go on for a while about how they work, but the short version is every > boat at the marina is wired together by the ground wires and is essentially > one giant boat. If your neighbors don?t have zincs, no problem, your zinc > will cover for them! It may not last long doing triple duty though ? The > galvanic isolator prevents this from happening. > > > First off, I did not argue that galvanic isolators do not work. They do. > I stated that the connection of AC and DC grounds is a main factor leading > to galvanic corrosion and thus the need for galvanic isolation. The only > reason for connecting the grounds is to provide an effective ground-fault > current path. Eliminate the need for an effective ground-fault current > path, eliminates the need to connect the grounds. Newer technologies > provide such a means. > > I argued that connecting AC and DC grounds is not needed for ground fault > protection if the vessel is protected by a ground fault circuit > interrupter(ELCI). This why the ABYC E-11 now requires all new vessels to > have such a device. The European ISO requirements (see extract from ISO > 13297 in my blog discussion) specifically states that if a RCD (another > name for ELCI or GFCI) or isolation transformer is installed then '' the > negative ground terminal of the DC system need not be connected to the AC > shore ground'' . I'm guessing the ABYC will eventually follow the ISO. > > My main point is that it is wise to install a whole-vessel ELCI. These > provide greater safety, and these are now readily available and more > affordable than fail-safe GIs. The Blue Seas A-Series ELCI Main Circuit > Breaker (model 3106100) which fits my Blue Seas panel costs under $150. > Fail-safe GIs cost well over $300. My very robust under $10 DYI GI was > installed in what I called a ‘’Fail-Safe installation’’. That is, it was > installed between the AC and DC grounds rather than breaking the AC ground > to shore and inserting there. The DYI GI, like the Yardina GI, is not > technically a ''fail-safe’’ GI, Yardina claims that they have no reports of > their GI failing. While these are very unlikely to fail, if it does fail, > it does not matter. The only reason I have not yet removed my DYI GI and > AC/DC ground connection is that it does not matter. > > Your discussion below is not correct . Specifically, the statement of > ''deadly hazard ‘’. A GFCI/ELCI would cut the power saving one from the > deadly hazard. But even without GFCI/ELCI protection, it is more deadly to > have a hot wire in one hand and then touch the DC ground if the AC/DC > grounds are connected then if they are not connected. That is, a deadly > AC current would flow better to the AC ground with the AC/DC ground wire > than it would with just an engine to seawater to AC ground connection. > > The actual reason for connecting the grounds is less for someone on the > vessel and more for the safety of swimmers. Yes, it is wise for a vessel > without a main ELCI to connect the AC/DC grounds and if doing so then it is > smart to use a GI. I would rather rephrase the last statement: it is > unwise nowadays for a vessel with AC shore power connection to not have a > whole-vessel ELCI. There is a reason why fewer companies are making > fail-safe GI. I initially wondered why a company like Blue Seas, which > provides practically any electrical need, does not provide a galvanic > isolator. But they do have this discussion on their website: > https://www.bluesea.com/support/articles/AC_Circuits/88/Green_Wire_%5BControversy%5D. > > > For convenience, here is my original link: > http://svjohannarose.blogspot.com/search/label/GalvanicIsolator > <http://svjohannarose.blogspot.com/search/label/GalvanicIsolator%3Chttps://protect2.fireeye.com/url?k=8c302211-d0a614f2-8c300b66-0cc47adc5fec-d02e08d2e81cb3ec&q=1&u=http%3A%2F%2Fsvjohannarose.blogspot.com%2Fsearch%2Flabel%2FGalvanicIsolator%3E> > > As far as not grounding the AC system to ships ground, this would be a > large and dangerous violation of ABYC regs and they exist for a reason. > In a perfect world boats would have isolated 2 wire AC systems with no > grounding at all. This is not the case presently and as long as various AC > devices not built specifically for boats exist we have to deal with > potential ground issues. Do not forget that the shoreside AC power *is not > isolated* and you are floating in a more or less direct connection to the > ground rod at the transformer and/or panel on shore. If some defective > appliance puts AC voltage on any part accessible by a human you now have a > hot wire in one hand and any part of the boats DC ground system is the > other half of the circuit. This can be a deadly hazard on a boat depending > on how good the green wire system on the boat and marina is and even if it > is good you still can get a considerable charge through you. The > interconnected grounds prevent this from happening. > The ONLY way I could see trying to make an isolated AC system besides for > an isolation transformer, which is actually a great idea but big and heavy, > is if the BOAT had an ELCI installed. You cannot count on every marina > having one at their end. > Joe > Coquina > C&C 35 MK I > > > > - > Paul E. > 1981 C&C Landfall 38 > S/V Johanna Rose > Fort Walton Beach, FL > > http://svjohannarose.blogspot.com/ > > > > > From: CnC-List [mailto:[email protected] > <[email protected]>] On Behalf Of Dreuge via CnC-List > Sent: Sunday, June 02, 2019 4:07 PM > To: [email protected] > Cc: Dreuge <[email protected]> > Subject: [EXTERNAL] Re: Stus-List Galvanic Isolators > > > > I would not spend much money on a galvanic isolator (GI). The main > cause of the galvanic corrosion is a result of connecting the AC and DC > grounds. Check if you have these grounds connected. Most older and > smaller vessels don?t have the grounds connected and don?t have galvanic > corrosion problem. Also, the industry is moving away from this requirement. > > One is better off investing in a whole vessel GFCI breaker(also called an > ELCI Main Circuit Breaker). These cost much less than a typical fail-safe > GI and provide galvanic isolation from stray AC currents by disconnecting > the power, and more importantly they provide much better ground fault > protection than connecting AC & DC grounds. > > If one still prefers bonding the AC & DC grounds then I would recommend > the Yandina GI or better, a DYI GI, and connect the GI between the AC to > DC connection to provide a fail-safe connection. > > I have a write up on my blog about this and also how to make a DYI GI, but > in short, don?t waste money on an expensive GI, invest your money in an > ELCI breaker, individual GFCI circuit protectors, and a decent marine > charger (not a cheap HF/Walmart/Amazon brand ) > > http://svjohannarose.blogspot.com/search/label/GalvanicIsolator > <http://svjohannarose.blogspot.com/search/label/GalvanicIsolator%3Chttps://protect2.fireeye.com/url?k=8c302211-d0a614f2-8c300b66-0cc47adc5fec-d02e08d2e81cb3ec&q=1&u=http%3A%2F%2Fsvjohannarose.blogspot.com%2Fsearch%2Flabel%2FGalvanicIsolator%3E> > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. 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