Will This Diagram Work?

[davisr]

I appreciate you making this clear Stu. Yes, if I read you correctly, I have indeed made plans to have the DC return wires from the anchor light, steaming light, etc. run all the way back to a DC consolidation bus beside the DC panels.

In other words, I have planned to completely segregate these anchor light, steaming light, etc. DC return wires from the mast's AWG 4 lightning ground wire (which leads directly down to the ship ground/ground plate).

There is only one wire in the entire DC system that runs to the ship ground/ground plate. That is the DC grounding wire (shown in green) on the main circuit diagram.

Thanks man for all the help,
Roscoe

[Stu Jackson]

Originally Posted by davisr

...

There is only one wire in the entire DC system that runs to the ship ground/ground plate. That is the DC grounding wire (shown in green) on the main circuit diagram.

As I read it, your AC ground AND your grounding wiring also leads to the grounding plate.

I posted that not only for the excerpt you chose, but to point out that maybe it's not such a good idea to have all three (AC, DC and grounding) going to the same place. Try reviewing that article again.

I don't mean to suggest I'm an expert of this stuff. Part of how I learned, not only "learned" on my own, but learned to provide links to other folks, was to read a lot and bookmark a lot!)

And your boat, with its outboard and unusual ground plate built-in, is a challenge. I just want you to be aware of the choices you're making, 'cuz I don't have an answer, and when i usually say "If it was my boat..." would apply only to those things I am sure of technically. In this case, i just don't know the right answer.

[mitiempo]

Roscoe

The galvanic isolator is installed in the AC ground (green) wire between the shorepower inlet and the 30 amp main double breaker.

[mitiempo]

Stu

The article by Stan Honey doesn't mention Roscoe's situation, but only covers an external keel/inboard engine boat. Stan has the lightning grounds to a keel bolt and the negative bus connected to the engine block as normal.

My opinion, were it my boat, I would keep the 4 awg wire from the mast at the connection for lightning protection and float the AC with no connection to DC negative at all.

[Stu Jackson]

Brian, I agree with your conclusions, only 'ceptin' that I don't know precisely what that ground plate is made of and how it was built, other than Roscoe's pretty good description. That's what I'd do, too.

It would be interesting to get Roscoe's take on his plans.

Hey, Roscoe, ya still dere????

[davisr]

Hey Fellas,

I've gone back and reread the Stan Honey article in the West Advisor.

The West Advisor: Marine Grounding Systems

I've also gone back an reread the thread that I've mentioned several times on Proper AC and DC Grounding.

http://www.cruisersforum.com/forums/...-dc-72432.html

Summary of Stan Honey's position

Stan Honey urges everyone (with inboard engines) to use the engine as the DC ground. He also urges everyone to run the AC grounding wire (the green wire) to this same DC grounding point on the engine (the inboard engine). Conscious of the issues that this create in terms of galvanic corrosion to metals on the exterior of the boat, such as the through-hulls, he urges everyone to install a galvanic isolator between the shorepower inlet and the AC breaker/panel.

When it comes to grounding for lightning protection, Stan Honey urges everyone to ground the mast with 4AWG wire to a nearby keel bolt/grounding bolt.

Stan Honey, therefore, urges everyone to have two separate grounding systems: 1.) DC and AC grounding sytem grounded together via the engine (the inboard engine); and 2) the lightning grounding system grounded via the keel bolt/grounding bolt.

It is worth noting that the position of Don Casey, Complete Illustrated Sailboat Maintenance Manual (2006) is similar to Stan Honey's.


Summary of Nigel Calder's Position (as quoted in thread "Proper Grounding for AC and DC")

In the initial posting for the thread "Proper Grounding for AC and DC" I quoted Nigel Calder's position on the subject of grounding. Nigel Calder states that it is a common practice to use the engine as the DC ground. He urges everyone, however, to use a single grounding point or "Common Grounding Point," as he calls it for DC, AC, and Lightning. This single grounding point should be connected to an immersed ground plate or strip made of copper. He explains all this and includes a sample diagram on pp. 232 and 233 of Boatowner's Mechanical and Electrical Manual (2005).


So where do I stand at present?

Given that I do not have an inboard engine that I can use as a ground for DC and AC, it seems that the best course of action is for me to follow the suggestions of Nigel Calder (and some others on this forum), and put DC, AC, and Lightning on a single point. This might create problems in terms of corrosion, but I suppose I could combat this with the galvanic isolator suggested by MiTiempo. A number of people in the thread "Proper Grounding of AC and DC" say that corrosion is of secondary importance to the protection one receives by having the DC and AC grounded together, especially if there is a problem with the grounding of the dockside connection at the marina.

So, that's my thinking . . .

Regards,
Roscoe