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Old 22-07-2013, 12:12   #46
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Re: Moving towards an AC boat

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Originally Posted by pbiJim View Post
There are 2 levels of GFCI protection available in the US that I am aware of. 10ma trip point is for protecting equipment. The more stringent 5ma trip point is for protecting people. Anything that you find at Home Depot, Lowes, or Ace Hardware is going to be 5ma class.
10, or even 30mA GFI do not just provide equipment protection.

In the USA the limit for GFI is 5mA. In Europe it is 30mA.
Unfortunately 5mA is too low for whole boat protection, but can be used on individual power points. This (or 10mA) is a good idea on deck areas etc

Almost all European boats have 30mA whole boat GFI. This is a very sensible system in my opinion.

There is a good discussion here:

Preventing Hazardous Ground Faults on Boats - Blue Sea Systems

Be careful with GFI devices they do seem to fail reasonably often on boats. Test them frequently.
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Old 22-07-2013, 15:03   #47
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Re: Moving towards an AC boat

I had read that 10ma was enough to induce a heart attack & that is why 5ma was chosen for the limit here in the US. I was unaware that Europe had a higher threshold standard. A 10 or 30ma system certainly would be more robust against nuisance trips. I'm not sure which would actually be preferable in practice. Thank you for expanding my knowledge base. Thank you also for that most useful link.
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Old 22-07-2013, 15:14   #48
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I had read that 10ma was enough to induce a heart attack & that is why 5ma was chosen for the limit here in the US. I was unaware that Europe had a higher threshold standard. A 10 or 30ma system certainly would be more robust against nuisance trips. I'm not sure which would actually be preferable in practice. Thank you for expanding my knowledge base. Thank you also for that most useful link.
Note that ABYC now mandates whole boat 30ma ELCIs as per European practice , it Europe code now requires multiple RCDs in the supply chain from premises mains , via dock post to boat.

Its why electrocution of swimmers is very very rare
Dave
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Old 22-07-2013, 15:41   #49
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Re: Moving towards an AC boat

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I agree variable frequency AC drives are a beautiful thing , I designed several in my earlier days ( 10% circuitry to do teh job, 90% protection circuitry to keep the MOSFETS alive!).
That was one of my early gigs too. My earliest designs used hall effect switches & TIP transistors to control power to little $35 DC brush motors in order to improve their efficiency & make them compete functionally with $200 PMDC brushless motors. That was back in the mid 1980's. Those crude circuits did the job they had to do, but when I look back at them now, they seem on par with a Ford model B. Post 2002, I stopped building any of that stuff. I now just buy what I need commercially. The stuff you can get off the shelf now for reasonable money is fantastic & in many cases, it nearly rivals servo performance. I'm a pretty big fan of Mitsubishi Drives for general dexterity & Lenze Drives for the really brutal applications. There are plenty of down & dirty cheap V/Hz drives out there for the simple applications too.
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Old 22-07-2013, 15:45   #50
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Re: Moving towards an AC boat

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Note that ABYC now mandates whole boat 30ma ELCIs as per European practice , it Europe code now requires multiple RCDs in the supply chain from premises mains , via dock post to boat.

Its why electrocution of swimmers is very very rare
Dave
Do you by chance have a link to the ABYC standards. It sounds like they are something that I really should read.

Thanks,
Jim
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Old 22-07-2013, 17:30   #51
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Re: Moving towards an AC boat

Couple of comments:

Stating that the motor in a 12V Danfoss compressor is multi phase AC is stretching things a bit much. To get the brushes, and their wear generated residues, out of the sealed unit Danfoss electronically commutates the DC input. One might state that the electrical current to the motor stator, it's a permanent magnet motor but the rotor is the magnet rather than the stator, is interrupted but since their is no voltage reversal
as is the case with what we normally perceive as AC it should not be described as AC.

The first municipal electrical power distribution systems were DC and they were fairly widely distributed however the demonstrated benefits of AC, easy voltage transformation, commutator free induction motors etc rapidly obsolescenced the DC systems. It was a bitterly fought war mainly between Edison and Westinghouse (I recall, but my recall is getting a bit iffy and I may be wrong) who had got control of the AC patents.

I tried to restrict my electrical appliance use on the boat to 12V DC for many years but found it was both impractical and expensive and just gave up and put in an inverter. I would much prefer to only use nice friendly and safe 12V DC in the small vessel marine environment for safety reasons but low cost DC appliances are just not widely available.
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Old 22-07-2013, 18:07   #52
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Do you by chance have a link to the ABYC standards. It sounds like they are something that I really should read.

Thanks,
Jim
http://www.bluesea.com/articles/1381

Or google ABYC e.l. 11.11.1

Dave
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Old 22-07-2013, 19:06   #53
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Re: Moving towards an AC boat

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The first municipal electrical power distribution systems were DC and they were fairly widely distributed however the demonstrated benefits of AC, easy voltage transformation, commutator free induction motors etc rapidly obsolescenced the DC systems. It was a bitterly fought war mainly between Edison and Westinghouse (I recall, but my recall is getting a bit iffy and I may be wrong) who had got control of the AC patents.
Your recollection is pretty good. That was the AC/DC war between Thomas Edison & Nikola Tesla (originally born Никола Тесла in Serbia). Tesla was a lunatic. He originally worked for Edison, then branched off on his own to pursue various innovations that Edison felt were too dangerous. His mechanical resonance experiments brought down a building in NYC where he rented shop space. His experiments with transmitting AC power through the air burned down more than 1 laboratory. When Westinghouse eventually backed him & forced him into putting his AC into a wire so that they could have somewhere to put a meter & charge for the power, he finally found his way into the good graces of history. Tesla was both brilliant & frightening. When he died, agents from the department of defense came & cleaned out the documents from his safe.

Surprisingly, the last vestiges of the old Edison DC system were still in use in parts of NYC as late as the 1990s. Then Con-Ed finally pulled the last plug & made the final few DC customers change over to the more efficient, and now standard, AC system.
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Old 22-07-2013, 19:12   #54
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Re: Moving towards an AC boat

Thank you for that link. That certainly provides me with a piece of the puzzle. I had hoped to find the comprehensive listing of all their standards. I had tried googling for them, but all I found was a place where I could purchase them. I did not find the web based PDF that I had hoped for.

Perhaps their standards are like the NEC, not really open to public observation, except to those who pay dearly for the privileged?
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Old 22-07-2013, 19:25   #55
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Re: Moving towards an AC boat

Dave,
That link seems to contain some conflicting information, unless I am misreading it. In the written description, it says "an ELCI provides additional whole-boat protection. Installed as required within 10" of the shore power inlet". Then the diagram below that passage is labeled, showing that the ELCI needs to be mounted within 10 feet, rather than 10 inches. Do you know of any way to determine which dimension is actually correct to the specification?
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Old 22-07-2013, 19:31   #56
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Dave,
That link seems to contain some conflicting information, unless I am misreading it. In the written description, it says "an ELCI provides additional whole-boat protection. Installed as required within 10" of the shore power inlet". Then the diagram below that passage is labeled, showing that the ELCI needs to be mounted within 10 feet, rather than 10 inches. Do you know of any way to determine which is actually correct?
http://www.paneltronics.com/atimo_s/...11Excerpts.pdf

7 inches or 40 inches in some cases.
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Old 22-07-2013, 19:34   #57
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Re: Moving towards an AC boat

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Perhaps [the ABYC] standards are like the NEC, not really open to public observation, except to those who pay dearly for the privileged?
That's essentially it. And, like most industry standards bodies, you can access the standards by buying outright (at um, high prices) or by joining the organization and paying... less-high prices

But fear not. The better marine electrics books (like Nigel Calder's book) provide good working summaries of the ABYC electrical spec.
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Old 22-07-2013, 19:37   #58
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Re: Moving towards an AC boat

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But fear not. The better marine electrics books (like Nigel Calder's book) provide good working summaries of the ABYC spec.
Do you have a title for that book?
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Old 22-07-2013, 19:41   #59
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Re: Moving towards an AC boat

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http://www.paneltronics.com/atimo_s/...11Excerpts.pdf

7 inches or 40 inches in some cases.
Dave
Thank you. That seems to be a much more comprehensive document.
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Old 22-07-2013, 20:12   #60
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Re: Moving towards an AC boat

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Do you have a title for that book?
Yup. Boatowner's Mechanical and Electrical Manual
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