Remote common ground or individual wire runs?

[sailboy21]

Getting really deep into my impromptu re-wiring project. Everything (AC, engine harness, positive main feeds, grounds coax, etc etc) was in one giant rats nest bundle. I separated the engine harness and coax cables, ripped out all of the AC wiring, now I am left with my main panel feeds and several miscellaneous grounds.

90% of my electrical devices are served by a ground strip in the battery compartment. My panel is about 3 feet away, and the wires lead through a bulkhead pass through. There are about 7 things that need a ground located physically above the panel, i.e. the ground must pass through the bulkhead with all the positive leads. I have had the understanding that each device should have its own dedicated ground wire all the way, not shared with any other devices. But, would there be any harm in establishing a smaller common ground connected to the main ground for these devices? My way of thinking is clearing up extraneous wires would be a benefit.

The devices that need a ground are: depth sounder, 2 cabin lights, bilge pump panel lights, hand held VHF charger, battery voltmeter and 7" LCD TV & TV antenna amplifier both from a 4 outlet cigarette plug. Probably no more than 1-4 amps at any given time, max worst case scenario is 40 amps from the panels master fuse.

[Hartley18]

My suggestion would be to install a ground terminal bar (a copper strip fitted with screw terminals) at the panel location - or at each panel location if you have more than one. Connect each individual device to the ground bar and connect a single ground wire from one end of the bar to a common ground point in the boat (usually a keel bolt or engine block).

This system is called a "single point ground" and, apart from being easy to check and faultfind, prevent earth loops that can wreak havoc with your radio gear.

The earth wires themselves don't have to be huge, but the common ground wire should be rated to the maximum current of the system - 40 amps in your case.

[sailingdog]

Provided the grounding wire coming off of the above panel ground buss bar is heavy enough to accommodate all the loads combined, I don't see a problem with it. However, each individual ground buss bar should be connected to the common ground directly and not to another ground buss bar.

If you use a terminal strip, the strip should be tinned copper, not plain copper. Using plain, untinned copper is generally a bad idea in a marine environment.

[k1vsk]

To add a comment to what Hartley said, a more insidious problem to be avoided is electrolysis or corrosion created by differing ground potentials which is a major reason for having a common ground. It is less important how they are interconnected as long as they are connected.

[sailboy21]

Thanks. I have a huge common ground for the 3 batteries and engine, connected with 4AWG to what used to be two copper straps literally screwed into the plywood bulkhead, no insulators or anything. Those are gone now, replaced with high quality ancor piece. I've been an animal lately. I have a garbage bag full of old thick strand copper wire and other misc tidbits from antiquity. Whoever wired this boat had a real fetish for zip-tieing EVERYTHING... amazing how many dead end and redundant wires I found.. Gonna have a new boat....

[sailingdog]

Don't throw the wiring out... it might be worth calling a scrap metal dealer, if you really have that much of it. Copper's pretty expensive at the moment...