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Old 24-07-2010, 00:07   #1
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ELCI and Isolation Transformer

Hi...

As with most projects aboard Nomadness, a simple-in-principle project is morphing into much more, tugged to and fro by trade-offs, legacy hardware, and related issues.

Nutshell summary: I'm installing a Charles 3.8KVA isolation transformer and removing the old galvanic isolator. It's a steel boat, and I've moved to a hot marina after a fresh re-zincing... I've wanted to improve the AC system for a while, and this pushes me over the edge.

At the same time, I'm replacing the old AC panel (the old one is in a very awkward and nigh-unserviceable location), and have a new Bluesea 8459 with two 30A source-select breakers and 8 branches. This will take over the role of the original AC selector switch. I'm also removing the old automatic transfer relay that has been there since the Olden Days; it's not only redundant but a potential source of trouble since my Outback inverter/charger does that just fine on its own. I am, however, repurposing the original source-select switch to pipe AC directly to the branch bus if all silicon gets toasted by lightning.

Leading up to my question... ABYC requires a shore-power breaker if there is more than 10 feet from the inlet (in my case, a new SmartPlug) to the connected equipment, and I have over 20. While reading the Bluesea support documents, I brought myself up-to-date on the ELCI (required on new boats about now), basically a whole-boat GFCI that trips at 30mA instead of 5mA like the ones we're used to seeing. But dang, they're pricey - about $100 more than a standard double-pole breaker (comparing the 1502 to the 8077).

I started wondering if it's really worth the bother in my case, since the only connected hardware is an isolation transformer. Ground faults are vanishingly unlikely in this scenario, and the ELCI seems redundant when leakage problems would almost certainly be on the other side of the big iron. Any thoughts on whether it would be overkill, both in terms of ABYC guidelines and practicality?

For context, my overall system includes AC from the shore connection, a 7.5 kW Genset, and the Outback FX2012 inverter/charger. The only power-related oddity is that I'm providing a 15-amp GFCI-protected AC output for my partner's much smaller boat, allowing her to hang off mine with a shore-power cord while on our shared end-tie (only one outlet) or rafted (sipping from solar/generator/inverter sources on my boat). This doesn't affect my ELCI question since it's downstream of the isolation transformer, but might, um, spark commentary as it is a bit unconventional.

Mostly I'm just trying to prevent superfluous purchases, and can't imagine the ELCI ever tripping with only the isolation transformer directly connected (unless I do a spectacularly bad wiring job, of course).

Cheers from Nomadness,
Steve
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Old 24-07-2010, 05:34   #2
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The presence of an Isolation Transformer (or Galvanic Isolator) does not negate the requirement for an ELCI.

ABYC E-11.11.1 states:
An Equipment Leakage Circuit Interrupter (ELCI) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E-11.10.2.8.3 whichever is closer to the shore power connection.

ABYC E-11 ➥ http://www.paneltronics.com/atimo_s/...11Excerpts.pdf

See Diagram 6 on page 13 (excerpts above).

See also ➥ http://www.powersigntech.com/Atimo_s...e_1st_2010.pdf
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Old 24-07-2010, 09:23   #3
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*sigh* OK, thanks, Gord. I know it's only required for new-boat construction, but if I'm doing surgery, I might as well bring her up to spec for some future survey......

Cheers,
Steve
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Old 24-07-2010, 10:06   #4
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Thanks, guys! I bought the Blue Sea ELCI a few months ago for the same reason as Steve (actually, I just wanted to be the first old boat in San Diego to have one). It's been sitting in my project parts crate waiting to get installed. Now would be the time, I suppose.
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Old 28-07-2010, 18:12   #5
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Still, it does seem really crazy to have a $170 ELCI (Bluesea 1502) whose sole mission in life is to trip if there is leakage in the 20-foot run between it and a Charles ISO-G2 isolation transformer. I'm really dragging my feet on this, given the $100 price difference relative to a simple 30A double breaker (Bluesea 8077). Is it just for new construction, or are all yachts expected to retrofit? I love the concept, of course, but with isolation it seems truly superfluous.

Not so with downstream GFCIs, I might add, since their ground is referenced to the hull and bonded AC/DC systems. I have those in the wet areas, including the one that is used for outside work on an extension cord.

Am I missing something here? If there is a good safety reason to go the fancy ELCI route, I certainly will. It is unambiguous in the ABYC document, but does that reflect an excess of caution and a bit of CYA given the wide range of installations and potential errors?

While I've got the floor, does anyone have experience with the new SmartPlug? I liked the look of it and bought one recently to retrofit my shore inlet and cord, but I've never gotten feedback from users. Having just last weekend replaced the shore outlet at the marina due to internal arcing when slightly stressed to the side, and having seen some badly burned ones and useless locking rings, it seems like a sensible idea.

Thanks again,
Steve
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Old 28-07-2010, 21:24   #6
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Microship-
Quote:
since their ground is referenced to the hull and bonded AC/DC systems.
ELCI's and GFCI's have nothing to do directly with the safety ground. The current being supplied on the hot leg is compared to the current being returned on the neutral leg. If the comparison is not withing 6 ma for a GFCI or 30 ma for an ELCI then the device trips to eliminate the leakage.

ELCI's (called residual current devices, RCD's) have been required in Europe for several years. The USA is finally climbing aboard. Your point about having an ELCI upstream of an isolation transformer has me thinking though.

Regarding the SmartPlug...I am a dealer and I believe they are a vast improvement over the "standard" plugs and receptacles that we have all grown up with.

Charlie
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Old 28-07-2010, 22:09   #7
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Originally Posted by CharlieJ View Post
ELCI's and GFCI's have nothing to do directly with the safety ground. The current being supplied on the hot leg is compared to the current being returned on the neutral leg. If the comparison is not withing 6 ma for a GFCI or 30 ma for an ELCI then the device trips to eliminate the leakage.
Ah, yes, I was sloppy with my wording there... you are quite correct.

Quote:
Originally Posted by CharlieJ View Post
Regarding the SmartPlug...I am a dealer and I believe they are a vast improvement over the "standard" plugs and receptacles that we have all grown up with.
Good - another vote for them. I first heard about them on Navagear, then found them for sale at Shurtz Marine where I just had a Micron 66 bottom job while hauled a couple weeks ago. Having always despised those twisty connectors of yesteryear, I decided to give it a try... it would have been a big decision, sitting at my computer, but on top of a bunch of yard work, it was a drop in the paint bucket!

Cheers,
Steve
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Old 29-07-2010, 10:09   #8
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Steve, you are absolutely correct. I will probably install mine despite the logic because I tend to experiment with the new technologies in order to appear slightly more informed than my customers, plus I can write it off as a business expense. I like to rationalize these experiments as R&D. That way I get to play with new toys and don't feel as guilty about spending too much money on new toys. The bizarre part is that if everything is well installed and there are no problems, I won't see any difference (not too rational, is it?).
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Old 31-07-2010, 14:27   #9
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Roy - I love that logic! I'm a master of rationalization also... I'll research to death some little $20 online purchase, but if it's something for the boat, then only the best will do (and NOW!). It's a sickness.

(The equivalent phenomenon in the music world is called GAS - Gear Acquisition Syndrome.)

Steve
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Old 31-07-2010, 15:21   #10
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WRT an ELCI on the shorepower side of the IT, I don't think one is required by ABYC. In reading the installation manual on the Charles 3.6kva, it shows 2 ways to connect it to the shorepower, one is with an ELCI and the transformer static shield connected to boat ground and the other way is with a normal circuit breaker and the transformer static shield connected to shorepower ground. The Charles manual states the figures they show are reprinted from the ABYC specs.

Take a look at:
http://www.charlesindustries.com/mar...R36T-1_PR3.pdf

I believe the ELCI would give you protection if your transformer shorted itself to it's static shield. Not sure what that would save you except maybe a big boom as a transformer with a short to it's static shield needs replaced, IMO.

I went ahead and used an ELCI on the shorepower and connected the static shield to boat ground, afterall, it's insignificant when figured in the price of the whole project, my IT is 6250va (not Charles).

BTW, I'm not sure there is much potiental difference between boat ground and shorepower ground. The water seems to be a pretty good shorepower ground (assuming you have a ground plate on the hull).
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Old 10-08-2010, 10:58   #11
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Yet another reason to add

Steve,
First good to see where you've been hanging out since the BEHEAMOTH days..

Second, the other reason to drop the bucks for the ELCI is what happened to me on my boat..

A few days ago we were sitting in the nice comfortable A/C watching TV and just loving life on the dock. Then suddenly everything electrical started freaking-out, smoke poored out of the fancy Xantrex charger and the shore power just died. What had happened was the neutural wire burned-up on the dock. We lost the TV, PC, router, cable modem, and PC monitor. Basically everything that could use the cable as ground tried putting 240v down the line.

My neighbor who has an almost identical set-up on his boat BUT has an ELCI lost nothing since the ELCI breakers tripped saving all his stuff.

Lucklily the TV had an older style "brute force" power supply that just popped a fuse, the PC power supply is cheap, the cable modem is rented so Comcast got to replace it, the router just needed a new "wall wart", but the PC monitor is shot. The strange part is that even though the Xantrex charger pumped an enourmous amount of smoke into the cabin, it just lost a couple of MOVs and is working just fine.

What we learned is that the next purchase for the boat will be a pair of ELCIs to protect us should that ever happen again. Fixing and replacing all this junk is an expensive pain in the but and shore power is never all that great.

Chris Smith
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Old 10-08-2010, 11:14   #12
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HI Chris...

Wow, what a nightmare! Glad it wasn't any worse.

I think the ELCI is a great idea, and indeed would have saved your electronics during that event. But would not an isolation transformer have done so as well? Since I had to get the latter anyway, I decided the ELCI would be redundant (or at least pretty sure!). Photo below shows what I did at the front end: a normal breaker about a foot from power entry (in the same enclosure). I'm very willing to be proved wrong, but I just can't think of any way an ELCI there would add any further protection except against failure in the isolation-transformer or the wires leading to it.

By the way, I haven't decided yet if that SmartPlug was a good investment, though it is clearly a more robust connector than the legacy type. I gave up interoperability to do that, but the main annoyance is that I had to grind and primer steel to get it in there... the body "corners" all interfered with the original mounting hole. Ya'd think that something intended to replace an existing standard would, oh I dunno, maybe FIT IN THE SAME HOLE.... *sigh*

But back to the isolation transformer - my new marina is famously hot, and I just took a video of a power-meter spinning merrily at the outlet feeding a derelict power boat with nobody aboard. It does that all the time; this is not a cycling refrigerator. Unless there's some serious hardware running down in the old wooden hulk, I think I'm looking at massive leakage into surrounding seawater. That expensive ISO-G2 is starting to look pretty nice.

Cheers!
Steve
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Old 10-08-2010, 11:44   #13
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Oh, by the way... looking at old TV cable lines hanging in the water by some of the slips, heavy with mussels and terminating in corroded splitters zip-tied to steel posts, reminds me to post a warning. These are ground returns as well, unpredictably making a connection between boat and shore ground. I never see any mention of these when people talk about electrolytic corrosion and related ills, but they are a serious hazard.

I don't know if anyone manufactures an isolator for TV cable, and it's not an issue for me since I don't watch the stuff anyway... but seeing this stuff draped all over the docks makes me uneasy.

Cheers,
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Old 10-08-2010, 12:04   #14
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Oh, by the way... looking at old TV cable lines hanging in the water by some of the slips, heavy with mussels and terminating in corroded splitters zip-tied to steel posts, reminds me to post a warning. These are ground returns as well, unpredictably making a connection between boat and shore ground. I never see any mention of these when people talk about electrolytic corrosion and related ills, but they are a serious hazard.

I don't know if anyone manufactures an isolator for TV cable, and it's not an issue for me since I don't watch the stuff anyway... but seeing this stuff draped all over the docks makes me uneasy.

Cheers,
Steve
I believe most appliances (at least modern ones) that connect to TV cable have the coax ground isolated from the power ground. But your idea of and external isolator would be the absolute way to know for sure.
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Old 10-08-2010, 12:17   #15
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I think you're right, DotDun, though it's probably worth checking if anyone has such a rogue path to the outside world. I can't offer much of a data point at the moment, but at my house I just measured 180mV AC between the TV coax shield and green-wire ground... although that is from the upstream side. Measured in isolation, the TV itself shows infinite resistance between its ground and the shield, and would thus be safe. Given that people buy standard domestic hardware and plop it on boats with no clear attention to the isolation issue, however, I would bet it's a potential source of trouble in some installations. If nothing else, I would want to be sure the metal case of a splitter does not happen to touch ground - until now, this never would have even occurred to me.

(I'm remembering a wiring harness fire on my BEHEMOTH bicycle ages ago - a short ended up finding its way home via the 2-meter antenna coax shield. I've been wary of such "non-obvious" power system return paths ever since.)

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