grounding question

[magna 6882]

I installed a couple of plugs for 12v down riggers. I wire two circuit breakers with 8g then ran the hot line with 10g. My question is the ground. I found that each side of the boat had all the thru hulls connected with a number 8g green wire. I also noticed the galvanic isolator was wired with with 8g wire.
I was thinking tonight that with two systems AC and DC do i need to rethink where i picked up the ground leg for the 12v down riggers?

 

[Comodave]

The green wire is the bonding system, not to be used as a 12 ground wire. Your ground wire should be run back to, preferably the main ground bus bar, or at least a ground bus bar with sufficient wiring that is able to carry the current flow from your downriggers.

 

[SteveK]

The green wire is the bonding system, not to be used as a 12 ground wire. Your ground wire should be run back to, preferably the main ground bus bar, or at least a ground bus bar with sufficient wiring that is able to carry the current flow from your downriggers.

Dave,
why does it matter where you connect the ground wire? The bonding if connected to negative of battery completes that circuit, so curious.

 

[Comodave]

Typically you will have a main ground bus bar. That is where the single connection from the bonding system is usually connected to. You don’t want multiple connections between the bonding system and the 12 volt ground. I suppose that it could be at the battery but I don’t like multiple wires connected to the batteries. I think it is a better, maybe more elegant, solution to run a large cable from the batteries to the main ground bus bar. It keeps the connections at the battery more simple and cleaner. Also it is easier to get a good clean connection at a bus bar away from the fumes of a flooded battery. At least that is my thinking, YMMV.

 

[Sleeping Bear]

Grounding

You absolutely should not connect grounds to your bonding system. Bonding is to neutralize the metal parts and avoid corrosion, if you connect a load you will cause changes to the potential in the bonding system and can cause catastrophic corrosion.

Your grounding system should be separate and yellow wires.

 

[mvweebles]

Good article by Steve D on AC neutral and grounding.

https://stevedmarineconsulting.com/neutral-to-ground-demystified/

 

[Shrew]

why does it matter where you connect the ground wire?

Because the ground circuit should be capable of carrying the current of the device.

The bonding if connected to negative of battery completes that circuit, so curious.

Because the bonding system, while tied to the ground, is not part of the ground circuit. You're now putting charge through your bonding system?

 

[C lectric]

By connecting any load to a bonding system you have changed it to an active conductor.
If there is even slight resistance along the bonding path after the load connection then that current may leak to the seawater creating a corrosion possibility effectively defeating the bonding.

 

[Byekurman]

My understanding is that the ground buss/bonding system is designed to only carry fault current!

 

[SteveK]

My understanding has been that the bonding system provides a path for dissimilar metals into an anode.
I can accept not interrupting that flow by introducing a charge. It is an interesting topic bonding to create that path.