Electric diagraming

[shemandr]

I've been reading the current issue of GOB and in particular the article on galvanic corrosion. There are a number of diagrams there that make little sense to me - since I don't speak electric. And, there have been any number of diagrams offered on this site regarding battery configuration and whatever else that make almost as little sense to me. Is there somewhere where the symbols in these diagrams are defined and could be book marked as a reference.
Also, I was stumped by the first assertion in the article that simply keeping the AC ground and the DC ground separate is dangerous and against standards. What is the shock hazard?

 

[Charles Erwin]

First- I have not seen the article so cannot comment on what might lead to confusion concerning galvanic corrosion. Never have encountered standard symbols in diagrams/articles discussing electrical layout.

As to the last question here is my take. DC ground and AC safety green need to be connected together. Here is why. If a DC wire comes in contact with AC current the DC system becomes energized with AC current. (This can happen via a battery charger internal fault, chafed/pinched wiring, possibly an overheated DC wire melts into an AC cable, possible wiring goofs, loose connections, etc. ) But -- you have connected AC safety green and DC ground together. What happens is the AC current (accidentally present in the DC wiring ) will follow the DC ground wire to the AC safety green where you connected them and then back to ground ashore.

Since AC is now flowing direct to shore ground through the safety green wire -- there is a short circuit and your AC breaker will trip. If there is no connection between the two, likely no breaker trip, and you will have live AC present in the DC wiring - only you would not know anything about it.

Charles

 

[Charles Erwin]

Found the article in Good Old Boat.

I think the MaineSail article at http://forums.sbo.sailboatowners.com/showthread.php?t=148402 is much better.

Charles

 

[kenn]

shemandr,

There are a number of good books out there that cover boat electrics and galvanic corrosion. Given your comments, this might be a good book for you:

http://www.amazon.com/Sailboat-Electrics-Simplified-Don-Casey/dp/0070366497

I refer alot to Nigel Calder's big book, but it's fairly technical and I already have an electrical background.

And MaineSail's posts are very valuable.