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Old 19-01-2018, 12:52   #1
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ground for AC

I'm replacing an existing 50amp AC electrical service with a 30 amp service. My boat is a Countess built in '69. The 50 amp service never had a ground. The instructions I found on line said to connect the ground to the designated connection on the engine. According to Yanmar one should never connect a ground to the engine. Any suggestions?
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Old 19-01-2018, 13:26   #2
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Re: ground for AC

Get an electrician
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Old 19-01-2018, 14:06   #3
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ground for AC

My AC and DC grounds are interconnected.
Don’t quote me, but I believe that is IAW ABYC.
Of course the DC ground is connected to the engine, or the starter or alternator wouldn’t work.
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Old 19-01-2018, 14:30   #4
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Re: ground for AC

This may help
https://www.westmarine.com/WestAdvis...unding-Systems
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Old 20-01-2018, 00:52   #5
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Re: ground for AC

Quote:
Originally Posted by john61ct View Post
Get an electrician

This...
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Old 20-01-2018, 03:21   #6
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Re: ground for AC

Greetings and welcome aboard the CF, aquastan.
Yanmar, as quoted, is wrong.
AC Gnd through Galv. Isolater to engine.
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Old 20-01-2018, 23:19   #7
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Re: ground for AC

it would go to the AC ground bus bar in the AC panel.

that bus bar should should also be connected to DC ground at the main DC ground bus bar or battery.

no wires should be grounded on the engine. except the engine ground wire itself.
an engine block should not be used as a bus bar.


I would wonder if you have grounds from the AC panel to all the outlets and appliances? if you don't, then you need to rewire the whole boat.
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Old 21-01-2018, 03:47   #8
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Re: ground for AC

ABYC E-11.17.1.4
The shore-grounding (green) conductor is connected, without interposing switches or overcurrent protection devices (See E-11.5.5.5.), from the shore power inlet to
11.17.1.4.1
an optional galvanic isolator, and then to
11.17.1.4.2
all non-current carrying parts of the boat’s AC electrical system, including
11.17.1.4.3
the engine negative terminal or its bus.
11.17.1.5
If an optional galvanic isolator is used, the shell of a metallic shore power inlet shall be electrically insulated from the boat.

See Diagram E-2

Note : The AC Ground bus (green wire) is connected to the DC Negative Bus.

From 2008* ➥ http://www.blackfinforums.com/sites/.../abyc-e-11.pdf

*This will likely disappear soon, so print it now if you'll be needing it.
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Old 21-01-2018, 05:49   #9
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Re: ground for AC

GordMay and A64, thanks for the links. Both PDF’s saved for future exploration of my boats wiring.......I love this site.
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Old 21-01-2018, 07:19   #10
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Re: ground for AC

While the ABYC recommends it, connecting AC and DC grounds is a contentious issue and other societies do not follow this practice. In my view it will kill more people than it saves, particularly if your boat is in fresh water.
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Old 21-01-2018, 16:33   #11
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Re: ground for AC

Quote:
Originally Posted by john61ct View Post
Get an electrician
Get a marine electrician
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Old 22-01-2018, 01:27   #12
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Re: ground for AC

On my boat all the AC appliances are double insulated, everything is in plastic, nothing even has a ground connection(modern equipment?), The RCD's are dual pole - Live and neutral and will trip, because i test them every now and then, besides NO one in their right mind would swim in my marina the water is disgusting and it's not allowed..I doubt that chances of a fail between the AC to DC side is even remotely likely(even then the RCD would trip) and so I disconnect my AC ground from the DC ground and stop the galvanic problem right there, it seemed almost every second marina we went to in Europe had a ground fault anyways where we WOULD suffer corrosion problems against the remote chance of an AC fault.
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Old 22-01-2018, 09:53   #13
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Re: ground for AC

Here is another article for you. Gord has posted the ABYC standards.
https://www.proboat.com/2011/10/demy...nd-connection/
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Old 22-01-2018, 11:06   #14
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Re: ground for AC

In the article's example, "Live Case" the RCD's will trip when the human earths the case even without the AC to DC grounding connection, or even if the marina's shore side ground is poorly maintained.

Putting a screw through the power cable and not shorting against Neutral while energizing the metal?! not plastic case - one in a million chance Darwin award.
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Old 22-01-2018, 11:07   #15
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Re: ground for AC

The Yandina galvanic isolator is only $99 plus shipping. It doesn't have an indicator light circuit to display the health of the isolator but they are "fail-safe" which means if they burn out then you lose isolation and not your ground connection.

Galvanic Isolator Explained

Disconnecting or not connecting the AC ground from the metal parts of the boat is just stupid dangerous. It's not worth the $100 saved, or even $299 for the isolator that WestMarine sells.

I went to trade school for 5 years to become a commercial electrician. I understand the arguments for and against the practice. I still think it is very ill-advised to purposely NOT connect the one wire that facilitates the operation of the over-current device in the case of a fault situation. The only way to do so safely is with the use of a fail-safe isolator.
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