Grounding questons

[KellyC]

I have a 67 Starcraft Islander that I am in the process of rebuilding and have a question. Is it ok to take a neg (-) lead from the battery to a small bus bar that will split and then go to the fuse box and a couple other things as well? I was thinking that as long as it is ground and not to the boat itself that it would be ok to do so. I do know that you should not ground anything to an aluminum boat but wanted to make sure that this idea was ok.
Thanks

 

[Pez Vela]

Re: Grounding questons

Your description of what you're trying to accomplish is rather vague as to "other things," and your inclusion of a fuse box in the negative circuitry doesn't sound right. I think you need to provide more information for the 12v system experts.

 

[KellyC]

Re: Grounding questons

Well lets see, fuse block has a + and - buss on it so I did not think that was an issue there. There may be another fuse block that will go to the ground buss that I was talking about, not to the - on the other fuse block. The reason for the second fuse block is that the first one is very small and I want all electrical items to have thier own fuses. That is the reason for asking about a buss that can branch off into at least 2 legs for ground.

Yes a fuse box or block does belong in the neg (-) circuitry as it has the ground buss of its own. The equipment has to be grounded, + from item and - from item both will go to the same fuse block to thier respective bus or fuse and then a larger gauge of wire will go to the neg (-) and one will go to the pos (+). I wish that I could draw it out but do not have anything to draw with here at work, not even sure I do at home either.

 

[grzzzz]

Re: Grounding questons

Howdy

A 67?? Me too. Been working on it 2 years now. It will be going in the lake this spring even if it is to push it off to watch it sink!! I put in a 2 battery system.. One batt to run "everything" and one just for motor starter. I have an isolator between them so there is never any feed back. You are always grounded to the boat. No way around it. The motor will always ground in some manner into the transom. There is just no way to isolate it. That does not say that you probably should not use the boat as a current carrier. There are plenty of ground to latch on to in the instrument cluster. Grab one there. That will carry your ground through your wiring harness back to the batt and keep a clean connection. No ground needed at the fuse box. Grounds will come of your "things"

Grzzzz

 

[Art Bernard]

Re: Grounding questons

It's not a problem to come off your batt to a rear mounted grounding strip than continue forwards to the fuse box ground connection. I will say though that you shouldn't ground to your boats hull. All grounds are to the neg terminal of your batt via your grounding strip in rear and ground strip in fuse box. Mine is set up this way and no problems. I use the ground strip in the rear along with a hot strip and fuse for my auto bildge pump, much less wire to run and worry about.

Art

 

[wifisher]

Re: Grounding questons

I think Art is right if I understand the OP correctly. I believe you are talking about running the ground to a buss bar that is attached to the fuse block. You are not going to run the ground thru a fuse. That is the proper way to set up your electrical system. Just be sure that the wire from battery to buss bar is large enough to handle the combined current from all of the ground wires coming to it.

A lot of people think that just because there is 0 volts that wire size does not matter. This is not true. Current remains the same on the ground side of the circuit, and therefore requires the same wire size.

 

[KellyC]

Re: Grounding questons

This is what I had in mind guys, and yes I will use wire size accordingly.

 

[wifisher]

Re: Grounding questons

That is much easier to understand. Yes, it will work wonderfully. Wire it up and get on the water.

 

[Silvertip]

Re: Grounding questons

Way too many points of failure in that scheme. The negative bus bar is not needed. Will it work? Certainly! The idea is that every connection you make is an additional point of failure. Wires are rarely the cause of failure. They need to physically break or short to cause a problem. It is the termination (ring terminal, crimp, solder or whatever technique you use) or the point where it is connected that fails. Therefore the bus bar has three points of failure by itself. Modern fuse/breaker panels incorporate both the positive and negative bus. Why not run the positive and negative feeds directly from the battery to the bus via an appropriate breaker in each positive lead. Use the switch as planned. All the bus bar does for you in the above diagram is eliminate one negative run of wire but it adds a bunch of failure points.

 

[KellyC]

Re: Grounding questons

So Silver, is this what you had in mind sir?

 

[ajgraz]

Re: Grounding questons

I dunno Silvertip, I think the use of a busbar depends on what you are trying to accomplish. I put a negative busbar in the stern of my boat real close to the battery, attaching all of my grounds to that busbar (the ground to the main fusepanel up front, plus grounds to all the stuff in the stern like the bilge pump, bait pump, anchor light, etc.). This was primarily for the purpose of shortening all the wire runs so as to reduce voltage drop to my devices...with the secondary effect of course of allowing the use of smaller wire.

I do agree it adds more potential failure points, but this is not an airplane, nor (I suspect) a trans-oceanic vessel. If the OP is making good terminal crimps and making sure to put drip loops in the wiring at the busbar, should not be a problem

 

[KellyC]

Re: Grounding questons

Nope, not a trans-oceanic vessel. Just a good ol fishing/cruising boat for the Columbia River. Ok, have not heard of drip loops? I do make sure that crimps are good and connections good as well.

 

[wifisher]

Re: Grounding questons

http://www.thevirtualboatyard.com/2009/02/keep-the-wiring-dry-with-a-drip-loop.html

All you need to know about drip loops.

 

[KellyC]

Re: Grounding questons

http://www.thevirtualboatyard.com/2009/02/keep-the-wiring-dry-with-a-drip-loop.html

All you need to know about drip loops.

Thank you very much for that wifisher, I was going to do that but did not know that is what it was called. And it explains it well. I was just going to do that because I have seen it done before and thought it was a good idea. Again thank you.

 

[Silvertip]

Re: Grounding questons

So Silver, is this what you had in mind sir?

Yes -- but the Negative jumper goes at the battery posts, not half way up the boat somewhere. You also need to understand that the jumper between batteries and the cables leading to the switch need to be the same size or larger than the battery cables going to the engine (provided of course that you feed the engine from the COM terminal of the switch.

 

[Silvertip]

Re: Grounding questons

Suit yourself, but there is no better grounding point than the negative terminal of the battery. Your boat may not be an airplane but it is prone to the same types of failures -- generally when you least expect it.

 

[KellyC]

Re: Grounding questons

Thanks for the help SIlver. Yea I was in a bit of a hurry and just left that part of the drawing there, I should have changed it to be right by the batteries. Yes I am going to use the COM terminal of the switch to feed the engine and I was going to use the same size cable from the switch to the engine, but if I need to go bigger then I can without a problem. Thanks again Silvertip, you are a very helpful person and this is one forum surfer that greatly appreciates it.