1978 260 Sundancer 12 volt house ground

Hello All, I'm in the process of rewiring and am separating the 12 volt house panel from the starting battery to it's own battery system. I'm going to use the old panel which has breakers for each circuit next to the switches. The panel itself has no ground connections, just the breakers and hot wires that jump from them over to the switches. So my question, which may be a stupid one I don't know, from the batteries run the hot to the panel and the negative post to a negative bus terminal for the grounds from each circuit, cabin lights, horn, etc.. Is the negative ground from the battery post sufficient as the ground for this? Thanks

I don't know but am following as I want to know as well.

LOL! Darn I thought I had an answer. I was able to test my old panel board this morning and all the switches work great. So I guess once I feel secure about a proper ground and finish identifying the rest of the spaghetti wires then I can start running circuits to everything.

OK, I was doing some research and have seen a number of ground systems, some which just say using the negative post on the house battery. However I came across one I think may be the better way to go. Basically you just run the house battery negative to the start battery negative post which is attached to the engine. Does anyone know if that sounds right? Would or could that be a problem concerning electrolysis? (I don't have a great understanding of electrolysis so I recognize that could be a ridiculous question)

So You are correct, all of the batteries should have there grounds tied together. But be carful on bonding if it exists.

Decent article on bonding etc. https://www.houseboatmagazine.com/2012/04/protect-your-boat-from-the

Going down a rabbit hole... Here's another with direct relation to our "hobby" https://shop.pkys.com/Dock-Ground-Fault-Breaker-Trip-issues.html

Nater Potater said:

Going down a rabbit hole... Here's another with direct relation to our "hobby" https://shop.pkys.com/Dock-Ground-Fault-Breaker-Trip-issues.html

Click to expand...

Great article on leakage current. Very important and over looked subject.

Thanks for the info. Good stuff.

Yes, there should be only one ground point in a DC system and all negative circuits should be connected to that ground. The engine is usually the ground point and battery negatives are connected to that ground point. You are right. It is better practice to have a negative buss bar, to which you connect the negatives, and a conductor from the buss to the negative ground on the engine. See the section on Grounds (about half-way down the page) https://newboatbuilders.com/pages/electricity2.html

As for the article on Houseboat, it is good but I wish they would stop using the term electrolysis. The correct term is stray current corrosion. Electrolysis is actually the reverse reaction. https://newboatbuilders.com/pages/corrosion.html

The article on leakage is excellent and a real problem that occurs at far more marinas that is realized. All it takes is one electrical fault in the shore power or on someone's boat. The result is deadly.

I was looking at the ground section in the article and you just answered another question for me. I redid my shore power which has a metal breaker box which is of course grounded. I was wondering about whether or not that was enough of a ground for that and I see the article says the shore power should also be grounded to the engine at the same point that the 12 volt system is. That sounds pretty spooky to me but there it is in the article. I didn't want the 12 volt system anywhere near the shore power. I was thinking the ship to shore ground in the receptacles and box was going to be enough.

They are confusing ground with grounding, which are two different things. The term ground refers to attaching the negative of a DC 12V system to earth ground (in this case the engine). The term grounding refers to the third wire (the green wire) in AC systems. The green grounding wire is the safety wire. The black and white wires (hot and neutral) are the only wires carrying current in an AC circuit. Black carries the current from the source and the white returns it to the source which is connected to ground at the source. The green is there only to carry current if there is a fault and you lose your return to ground. The only place on a boat where the white and green (grounding wire) are connected is the boats ground. This does not introduce current into the DC system or into the water. It only provides a low resistance path back to the source so the current doesn't accidentally go to ground through you.

As far as the metal breaker box on a boat goes it should not be grounded. There should not be any connection between the box and the electrical system on the boat. The box should be isolated from the DC or AC system. It is common on house systems to ground the box, but is not good practice on boats. There is no need to ground the box, it is not part of the bonding system which connects all metal fittings in contact with water to place them all at zero voltage potential, to avoid galvanic corrosion. By connecting the box to ground, if there is a fault in the box, you risk introducing stray current into the ground (and into the water around the boat.)

Also, inside the breaker box, if both DC and AC are inside, they must be separated by a non conducting shield and the AC components need to be shielded from accidental contact by tools, or body parts (fingers, hands, whatever).

Rayfor said:

... I see the article says the shore power should also be grounded to the engine at the same point that the 12 volt system is. That sounds pretty spooky to me but there it is in the article. I didn't want the 12 volt system anywhere near the shore power. I was thinking the ship to shore ground in the receptacles and box was going to be enough.

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So this is a topic of much discussion, but in short yes they get tied together, and no they never get tied together. Let me explain.

The boats ground plain or bonding consists of the AC green wire which is supposed to be earth ground only and the DC ground, this should also have a bronze bonding plate that does not get painted and is a bolted through the hull, the plate side to the sea water and the bonding wires to the bolts inside. The white ac neutral wires should never be tied to the bonding in any way what so ever as that carries ac voltage/current. The dock side power needs to be brought to the ac panel of the boat, but needs to have a galvanic isolator (zinc saver) between the dock side green ground and the boats bonding system. This is the old way of connecting AC. The more modern connections and correctly so, use an isolation transformer the remove the green wire from the dock altogether and leaves the boat isolated from the dock. It's a bit more complicated then that but these are the basics.

I've been wiring my boat off and on (no pun intended) for 5years, and am now (almost) qualified for a Phd. in electrical engineering!!