12V Negative - Shared or Per-Circuit?

[sainted]

Oh, one other thing. You should use triplex for ac wiring whether or not you use primary wire for the dc circuits. ABYC requires that the ac conductors be bundled separately from the low voltage stuff, and using triplex fulfills that requirement.

[Cheechako]

I think I like the buss bar approach. Duplex wire is insanely priced compared to single wire.

[alx]

Originally Posted by Cheechako

I think I like the buss bar approach. Duplex wire is insanely priced compared to single wire.

I don't mind the price if it's the right thing for the boat. My problem is that duplex is much thicker, and bringing a lot of wires into my fuse console it's hard to get them all together neatly. Using primary wire would allow me to use a thicker gauge (likely 12AWG) for the whole boat as opposed to just select "heavy" circuits.

Originally Posted by sainted

Oh, one other thing. You should use triplex for ac wiring whether or not you use primary wire for the dc circuits. ABYC requires that the ac conductors be bundled separately from the low voltage stuff, and using triplex fulfills that requirement.

Already do I only have one AC circuit after the panel - and that's the battery charger. The panel itself has the boat's only AC outlet.

[sparrowhawk1]

It's been a while since I've read it but Nigel Calder who is a boating guru Wired his boat with several circuit breaker panels. for example one towards the stern one in the middle and one towards the bow. With heavy gauge wire that is fused close to the battery supplying the panels and then duplex from the fuse boxes to the individual loads. This not only saves costs and is easier than running duplex from one end of the boat to the other but it makes troubleshooting much easier.

[Captain Blue]

The cleanest way is what a64pilot said

[deblen]

Bus bars,sub panels,etc-the cost adds up.
If you are doing a complete re-wire,I suggest buying a 500ft reel of duplex 16ga. & feeding each load separately.
By going with 16ga (10amps @ 12V cap),wiring is smaller & more flexible per run. 10 amps (120watts) will easily supply any lighting & electronics.

Yes-you will need the odd run of heavier ga. for A/P pump,etc.

Not criticizing the A64pilot method-it will work fine,but I noted the comment by OP? about the high cost of duplex cable. If bought in 500ft reel,it is reasonable $210. IMHO

Wire Tinned Standard 16/2 Flat Red Black 500' Spool

[alx]

Cost is not really a factor in my decision - I don't anticipate that either option will be vastly more expensive than the other.

I'm trying to determine what's the best option in terms of reliability and usability. It seems like the popular vote is for a distributed negative bus with a large enough "backbone" and primary positive wiring.

[trifan]

Here are a few more thoughts about rewiring a boat:
Although there probably won't be any issues with running duplex wire from the panel to loads, consider what happens if, for some reason, there is enough current in the load to cause the negative terminal of that load (the "ground") to differ somewhat from the negative of an adjacent circuit, say a few millivolts, which isn't much but what if a sensitive piece of electronics in one circuit is cabled to a sensitive piece of electronics in a different circuit and you have the grounds of each differing a bit? It might make a problem, it might not. It depends on the equipment but I have seen people almost go nuts trying to resolve a problem like that and never suspect it was the power causing the trouble. Yes, I had a previous life and, yes, it involved crap like that. Distributed grounding using busbars is the best approach as it keeps the ground plane impedance to a minimum. (A good thing).

Once you get the wiring done, then work on your lightning suppression so those electronic gadgets (and you and yours) don't get fried. You know, faraday cages, through-hull side-discharge electrodes, etc.

Good luck!

[wooden head]

I ran a combo of bus bars and duplex wire. Bus bars at helm, by fuse panel and amidships lights only amidships both hot and negative the positive bars divided by breaker circuit. Common ground. Negative bus by helm and breaker panel to help simplify multiple conections in a close area. Bundles of wire should be split into small bundles, (I keep it to three wires) to protect from heat failure. A wire in the middle of a bundle cannot disipate heat efficiently and can greatly reduce amp rating.

Sent from my SM-N910T using Cruisers Sailing Forum mobile app

[sainted]

Originally Posted by alx

I like the bus bar concept, though I'm wary of giving up the protection of double insulation that duplex wiring offers.

Yes, according to the ABYC standards, primary wire must be protected from chafe. The sheathing on duplex or triplex wire fulfills that requirement. To protect primary wire you can run it in conduit, which isn't as hard as it sounds. Flexible PVC conduit is easy to slide over primary wire. You also have to support wire (any kind) every 18".

[deblen]

Originally Posted by wooden head

I ran a combo of bus bars and duplex wire. Bus bars at helm, by fuse panel and amidships lights only amidships both hot and negative the positive bars divided by breaker circuit. Common ground. Negative bus by helm and breaker panel to help simplify multiple conections in a close area. Bundles of wire should be split into small bundles, (I keep it to three wires) to protect from heat failure. A wire in the middle of a bundle cannot disipate heat efficiently and can greatly reduce amp rating.

Sent from my SM-N910T using Cruisers Sailing Forum mobile app

Good point on the bundling & heat dissipation. I've never been keen on lashing wires/cables every 6" or less for the sake of a super neat look.
Lash enough to avoid entanglement or abrasion in open areas. In cupboards or other normally non visible areas,slack up on the lashing.Use only enough to avoid abrasion/entanglement.
If wires are sized & fused properly,there will be no heat problem in individual wires.
You will appreciate this when you have to chase a wire later.

[jeepbluetj]

The conduit thing is where I like duplex better. To me it's just simpler to trace a duplex wire back then a separate ground and +v. Since I'm an engineer, I like to make debugability easy.

OTOH, I've got a 30 foot boat, and everything "long" was put in there 35 years ago by Catalina, so my new runs have all been pretty short. (I rewired the entire boat, except for the existing light circuits. they were embedded in the deck and I didn't feel like changing those out. The 110v stuff was a disaster, replaced every bit of it.)

On a larger boat I'd likely distribute several panels. Then home-run each load to a localized panel. Windlass gets it's own stuff.

It probably depends on the layout of your boat, the loads, and where you need to run wire.

[DeepFrz]

Here is what ABYC says about it. I think best practice is to use duplex cable. Run a + (fused/cct. brkr) and - cable of same current carrying capacity to each distribution panel (if using more than one panel) and then duplex or two wires from each fuse/cct.brkr to each cct. Some items need to have the ground wire run directly to the main DC bus or the main engine bus.

Using combined DC return (-) wires is very poor practice and will not enhance problem resolution in the future and is against ABYC recommendations.

11.5.2. REQUIREMENTS FOR DC
SYSTEMS
11.5.2.1. Two-Wire System - All direct current
(DC) electrical distribution systems shall be of the
two-wire type. (See Figures 9A and 9 B, and Figures
10 A and 10 B.)

[sparrowhawk1]

Originally Posted by DeepFrz

Here is what ABYC says about it. I think best practice is to use duplex cable. Run a + (fused/cct. brkr) and - cable of same current carrying capacity to each distribution panel (if using more than one panel) and then duplex or two wires from each fuse/cct.brkr to each cct. Some items need to have the ground wire run directly to the main DC bus or the main engine bus.

Using combined DC return (-) wires is very poor practice and will not enhance problem resolution in the future and is against ABYC recommendations.

That's pretty much what I recommended. But could you explain why some grounds have to go to the "main bus bar"

[DeepFrz]

sparrowhawk1, I believe its just for fuel tank sending units but not sure if that is the extent of it. Although that may be for gasoline tanks but it doesn't differentiate between diesel and gasoline.