Electrical lesson - been awhile

[pstephens46]

Boat wiring question. Regarding the buss bar and associated grounds. Does your buss bar connect directly to neg from a battery? Or is the ground achieved in some other fashion?

[Bateau_CX19]

Bus bar just gives you a neater solution for multiple connections. Bus bar can be used on either or both positive and negative. If all you wanted to connect was a motor to a battery, there would be little need for bus bar. However, in reality you want to hook up lots of things. By connecting your battery to a bus bar, you only need one connection to the battery for each positive and negative. Now you can make all of your other connections to the bus bar rather than directly to the battery.

so, I guess the answer to your question is yes, the negative bus bar, if used, would connect directly to the battery ground. You would then connect all of your other grounds to the bus bar. As a caveat to this, if you have an ammeter in the wiring to measure current, the shunt has to be placed in the main ground connection if you want to measure all consumed current. In this case, battery negative->shunt->negative bus bar->negative circuits from boat.

[rodbolt17]

then you have a bonding circuit that is separate from the buss ground if you have a metal fuel fill,metal tanks and various sea****s and running gear.

[TownsendsFJR1300]

Plus 1 ^^^.

My battery is at the rear of the boat (I use the stock, short Yamaha battery cables).

I then ran a separate heavy duty line (black and red) up to the center console. It's tied direct to the battery, a positive and negative to each side.

I think I have 6 or 8 attachment points and I use ALL of them: GPS, depth finder, stereo, marine radio, two separate cig lighter type outlets (in the glove box).
Each positive line from say the radio, is fused before it gets to the buss bar. Much, much neater under the console and all lines are labeled.


Now this is separate from the boats, stock wiring etc, just for my added on accessories...

[DennisG01]

Not knowing all the specifics on the boat, it's also a possibility that you may find a secondary bus bar. Meaning, the first one comes off the battery and the a second bus bar comes off the first one.

FYI (please double check me on this), but I believe that any positive cable must have circuit protection. For the example that Scott gives, the positive cable that feeds his fuse panel (GPS, etc) should have a circuit breaker or large fuse inline and within a foot or so of the battery (I forget the actual distance, but it's pretty close). This protects that feed cable - probably 8g or 10g.

[TownsendsFJR1300]

Not knowing all the specifics on the boat, it's also a possibility that you may find a secondary bus bar. Meaning, the first one comes off the battery and the a second bus bar comes off the first one.

FYI (please double check me on this), but I believe that any positive cable must have circuit protection. For the example that Scott gives, the positive cable that feeds his fuse panel (GPS, etc) should have a circuit breaker or large fuse inline and within a foot or so of the battery (I forget the actual distance, but it's pretty close). This protects that feed cable - probably 8g or 10g.

I considered putting a fuse in the main line but between the line running up thru a fiberglass orifice, the thickness of the insulation (of the wire) and that everything else is fused, I decided against it.

Un-less you actually short out the buss bar the wire should be fine. I didn't want to loose EVERYTHING (GPS, marine radio, etc) should that "main fuse" go out for some reason. There's absolutely no metal or anything to wear thru that HD line and runs direct from the battery to the bar. The heaviest draw (largest fuse), is a 10 amp for the cig outlets (for a spot light mainly).
I put two separate sockets, separate lines, separate fuses should there be an issue with one.

Been this way since about 2000.

Of course a fused line would be safer, but with each electronic unit separately fused, shouldn't (hasn't been)be an issue (in 18 years)..

[TownsendsFJR1300]

Not knowing all the specifics on the boat, it's also a possibility that you may find a secondary bus bar. Meaning, the first one comes off the battery and the a second bus bar comes off the first one.

FYI (please double check me on this), but I believe that any positive cable must have circuit protection. For the example that Scott gives, the positive cable that feeds his fuse panel (GPS, etc) should have a circuit breaker or large fuse inline and within a foot or so of the battery (I forget the actual distance, but it's pretty close). This protects that feed cable - probably 8g or 10g.

I considered putting a fuse in the main line but between the line running up thru a fiberglass orifice, the thickness of the insulation (of the wire) and that everything else is fused, I decided against it.

Un-less you actually short out the buss bar the wire should be fine. I didn't want to loose EVERYTHING (GPS, marine radio, etc) should that "main fuse" go out for some reason. There's absolutely no metal or anything to wear thru that HD line and runs direct from the battery to the bar. The heaviest draw (largest fuse), is a 10 amp for the cig outlets (for a spot light mainly).
I put two separate sockets, separate lines, separate fuses should there be an issue with one.

Been this way since about 2000.

Of course a fused line would be safer, but with each electronic unit separately fused, shouldn't be an issue (hasn't been) in 18 years..

[DennisG01]

Sorry, Scott, I wasn't using you "specifically" as the example - nor was I implying you did or did not fuse the main wire. I was just using what you wrote as a base example to add some information for anyone reading this thread down the road. I'm pretty sure it's a USCG regulation to have all positive lines fused - to protect the line from overheating/burning. But I also think it'd be a pretty rare case for this to happen in your scenario. You said that chafing is not a concern. The only way that I can, personally, think of there being an issue would be if the main line started to internally corrode a bit (increases resistance/heat) to the point where using multiple items at once caused too much of a draw and the wire started heating up. But again, that's a going to be a pretty rare case - although in some environments (and maintenance levels) it could be more of a reality.

[TownsendsFJR1300]

Sorry, Scott, I wasn't using you "specifically" as the example - nor was I implying you did or did not fuse the main wire. I was just using what you wrote as a base example to add some information for anyone reading this thread down the road. I'm pretty sure it's a USCG regulation to have all positive lines fused - to protect the line from overheating/burning. But I also think it'd be a pretty rare case for this to happen in your scenario. You said that chafing is not a concern. The only way that I can, personally, think of there being an issue would be if the main line started to internally corrode a bit (increases resistance/heat) to the point where using multiple items at once caused too much of a draw and the wire started heating up. But again, that's a going to be a pretty rare case - although in some environments (and maintenance levels) it could be more of a reality.

No problem Dennis and good points... Both end connectors/wires are greased with di-electric grease (as are the battery terminals) so I'm really not concerned about corrosion starting in the middle of the line...

It's extremely rare I go out at night, (maybe 3 times in 20 years), so the load on the wires (from accessories) are minimal. And I did forget, I do have a 6 gallon fresh water tank (under the CC) and 12 volt pump for it which is probably the biggest draw, and again, that pump is fused BEFORE it gets to the buss bar...

The less connections there are, the less points for failure (KISS)…

[Jason2tpa]

Boat wiring question. Regarding the buss bar and associated grounds. Does your buss bar connect directly to neg from a battery? Or is the ground achieved in some other fashion?

My understanding and use of a terminal bus bar is simply an extension of a battery terminal. The neg or pos battery terminal is "extended" to the corresponding neg or pos bus bar terminal via a conductive conduit. That conduit is wire/cable. The bus bar itself is just a piece of plastic with a conductive metal strip that extends the length of the plastic strip...threaded holes through the plastic.

[TownsendsFJR1300]

Sactly ^^^^^

[Bateau_CX19]

The requirement for fusing is from ABYC and is known as the 7/40/72 rule

Mounting placement dimensions for a fuse or circuit breaker (7"/40"/72" ABYC rule): 7 inch maximum if the conductor is not housed in a sheath or enclosure in addition to the wire insulation, 40 inch maximum if the conductor is housed in a sheath or enclosure in addition to the wire insulation, 72 inch maximum if the conductor is connected directly to the battery and housed in a sheath or enclosure in addition to the wire insulation.

Always a good idea to fuse a battery cable although the rules allow the motor starter circuit to remain unfused. The fuse is sized to protect the cable so each time a secondary run is made from a distribution point, ie a bus bar, a new appropriately sized fuse should be used. Better to blow a fuse than have a fire.

[99yam40]

yea, have you ever had smoke rolling out from under the dash on a boat while out on the water?

I was in a friends boat in the surf when smoke let loose.
good thing he had a battery switch we could turn off.

hard to find the proper wrenches when in a hurry to disconnect the battery

Best I can remember it was a cigarette lighter type of plug that went south,probably for a spot light or other power to something
not sure if it was fused or not

[zenoahphobic]

yea, have you ever had smoke rolling out from under the dash on a boat while out on the water?

I was in a friends boat in the surf when smoke let loose.
good thing he had a battery switch we could turn off.

hard to find the proper wrenches when in a hurry to disconnect the battery

Best I can remember it was a cigarette lighter type of plug that went south,probably for a spot light or other power to something
not sure if it was fused or not

Yes fuses don't necessarily stop fires.
Makes you think whether a conveniently dash located Red Button should be made to cut the battery(s) off right at the positive terminal(s). Only problem is that it and it's wiring needs fire protection; and adding a solenoid at the battery adds to greater maintenance liability.