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Grounding Question

Old 03-04-2012, 06:34 PM
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Since i have outboards and they are grounded, can I attach my electronics to the negative on my battery terminal? Does it matter where i attach them? Meaning, not directly to the negative terminal on the battery but on another negative wire from a different electronic device?

Also, is this grounding (green) necessary on electronics? When I read directions they make it seem like its code but not necessary.
Old 03-04-2012, 06:48 PM
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The problem with connecting at the battery directly is the connection itself. For me, I want a good strong connection to a buss bar, that I can then add additional wiring to. If all these connections are made at the battery, it is harder to make them properly as the ring terminals are stacked one upon the other. I would prefer fewer wires with a better, tighter connection.

Also, I don't use the wing nut connector..use a hex head nut and tighten sufficiently.

As far as color, I usually use black for negative. and most of my past boats were factory wired using black as the common or negative wiring.
Old 03-04-2012, 07:17 PM
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Yea, I noticed that wing nuts are not very common anymore. Makes sense to have a better connection with hex.

My question is about the grounding wire (green), not negative (black). Some of my electronics have both. I assume I can just attach the ground to a negative bus bar as well and not have any problems?
Old 03-04-2012, 07:29 PM
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As long as you are talking 12v DC, then yes....the ground bus that connects to the negative lead on the battery is the only "ground" on a boat. But if the boat has a generator and/or shore power connections, then that grounding system is completely seperate from your DC source and ground...

We are not talking about lightning or rf grounds either...
Old 03-11-2012, 08:02 PM
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let me ask my question this way...My Furuno Sounder has a Negative Wire to connect to Negative battery terninal. It also has a GRND (ground) wire connection for hooking up where? If a battery is the only ground/negative then why do i need to hook both (Green) GRND and (Black) Negative to the negative buss bar? Wouldnt just the Black suffice? Is hooking up the Green wire a must do in my application? ;?
Old 03-11-2012, 08:59 PM
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The green wire isn't required in your application. It's a Furuno thing ... ;?
Old 03-12-2012, 05:58 AM
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Originally Posted by triumphrick View Post
But if the boat has a generator and/or shore power connections, then that grounding system is completely seperate from your DC source and ground...
If your boat is wired according to ABYC rules, the DC grounding system IS connected to the AC ground.

You should have a DC grounding bus, physically separate from the DC negative bus, that would be used for DC equipment ground connections. It is generally unnecessary to connect electronic equipment grounds although it can help in cases where you are experiencing interference problems.

Eric
Old 03-13-2012, 11:07 AM
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Thanks Eric,
Thats what i was wondering...it may help with interference.
Old 03-13-2012, 10:33 PM
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Deanboy21,

Are you describing the Green wire that is the grounding/bonding wire for your bronze thru hulls, bronze strainers, bronze seacocks, etc. on your boat?

Also, on newer boats they use Yellow for the ground/negative cables for the battery ground.

Please tell us what year, make, and model boat you have so we understand exactly the question we are answering. Pictures would also help.

If you have an A/C electrical system on your boat it will have green for the grounding system as well, but totally different than the bonding system.

Maybe Seabob can chime in.
Old 03-15-2012, 03:24 PM
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Its a 2000 28ft Contender. All DC system. My new Lowrance electronics says if no grounding device then to connect the GND wire to to the negative on the battery along with the black wire. I do see some wires screwed onto the bronze thru hull then attached to the motor mounting bolt when i look up under the deck.
Old 03-15-2012, 04:20 PM
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Originally Posted by deanboy21 View Post
Its a 2000 28ft Contender. All DC system. My new Lowrance electronics says if no grounding device then to connect the GND wire to to the negative on the battery along with the black wire. I do see some wires screwed onto the bronze thru hull then attached to the motor mounting bolt when i look up under the deck.
The green wires attached to the thru hulls is a bonding system not a ground system. In your case I would bet that there is no connection between anything 12 volt other than possibly the engine block itself. It would be possible to attach the ground wire from your electronics to the bonding system but I would not recommend it. The bonding system is there to eliminate any difference in potential between under water metal items to protect them from electrolysis. I would attach the green wire from the electonics to the 12 volt negative only if you are having issues with interference.
Old 03-15-2012, 04:30 PM
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Using the grounds on your DC electronics really depends on the vessel type they are installed on. Grounds are meant to protect the equipment and eliminate noise. For commercial applications, we ground electronics to the hull in the event of lightning strikes. Yet the hull is normally steel or aluminum.

You don't have to ground the electronics on a fiberglass hull, but if you really want to then install a bussbar with individual connection points on the buss for each piece of equipment. The bussbar will effectively act as an anode. Never daisy chain grounds between equipment, mainly because if you take a lightning strike to an antenna, the strike has potential for smoking everything daisy chained. Hope this helps
Old 03-15-2012, 04:44 PM
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The electronics "ground" is a ground plate set in the water (in some cases a capacitance ground), with screen or metal inside of the hull. This is more related to RF interference--and not to the green or bonding wire in the boat.

Most small boats do not have a ground system.

But if you do--with a lightning storm, you should disconnect all power supplies (positive and negative, plus grounds as well as antennas. It is not just daisy chained electronics which will be damaged by lightning strikes. Lightning can come form a lobe which strikes in the water nearby, and travel up thru the entire ground system. I am aware of several boats where just this happened with many thousands of dollars of loss in both the electronics and electrical systems.
Old 03-16-2012, 10:40 AM
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Originally Posted by sickcat View Post
The green wires attached to the thru hulls is a bonding system not a ground system. In your case I would bet that there is no connection between anything 12 volt other than possibly the engine block itself. It would be possible to attach the ground wire from your electronics to the bonding system but I would not recommend it. The bonding system is there to eliminate any difference in potential between under water metal items to protect them from electrolysis. I would attach the green wire from the electonics to the 12 volt negative only if you are having issues with interference.
I think i understand now. I had a feeling for my 12 volt setup on a smaller 28ft boat that the GND could be used for interference issues. Maybe I will try everything and see if there are any problems before I connect them. Or, maybe just connect the Lowance DSI unit since it may be sensitive to the big Furuno ducer i have.

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