Electrical Bonding

[Scott MacCready]

While working on my new boat and otherwise inspecting things, I noted all of the large guage copper wire that used to connect all the seacocks, the mast, and the engine block, has been disconnected by the previous owner. All the wires are there, just unbolted. Is there a logical reason for this? I figure maybe he followed the school of thought that a well-grounded boat increased the chance of a lightning strike. thanks, Scott

[marv brinn]

all of the parts need to be bonded electrically so that there is no galvanic reaction ,no removal or depositing of material thru the electrolysis of salt water. ask the prior owner why that was done..I would be very curious about that answer.

[Sal Randazzo]

The question of whether or not to ground your boat is controversial, because as you say, boats that are well grounded are supposedly more likely to get hit by lightning. However, if your boat is well grounded, you are supposedly less likely to sustain injury or damage to your boat. It's a real catch 22 - You're damned if you do you and damned if you don't. However, running the ground wires to the seacocks is a no-no. The powerful electrical surge caused by lightning can blow out the seacocks and sink the boat. Most of the articles I've read reccomend using 4 gauge copper wire tied to a 1 foot square copper plate on the bottom of the hull.

[marv brinn]

I'd like to hear from the readers of this string . I have always thought that the bonding was an essential part of keeping all parts at the same potential . I would go with the way that the majority of boats are built.If lightining strikes it will find its way to the seacocks anyhow
What say you LaVida??

[Dalton]

Robinhood still grounds everything including through hulls.

[rtbates]

Isn't the reason you want all your water contacting metal to be joined and grounded is to make 100% sure that any stray current passes thru the sacrificial zinc and not your bronze seacock.

What I have found concerning grounds on Seraph is that I don't like having the AC ground connected to the DC ground. Being a very simple boat with the only AC being the battery charger and the AC outlets, I've taken out the AC-DC ground connection wire.
Why I did this? At my old slip I was tripping the dockside AC ground fault whenever I hooked up the AC line from the boat to the dock's outlet. I found that if I disconnected the boat three slips down from the AC system this went away. I also found that when plugged him in I could read AC voltage from the docks ground to the water around his boat! Apparently the AC current in the water would travel thru the ground bonding system on Seraph back thru the AC neutral and trip the ground fault. When I removed the jumper wire connecting the DC ground/bonding ground from the AC ground all was OK.

[M. R. Bober]

I think that you may have set up a potentially dangerous situation. A galvanic isolator or an isolation transformer would be safer alternatives in the event of short in an AC device.

I know that there a many opinions on the subject (and many regulations in place around the country). I'm curious as to the thoughts of our "on site" experts.

Mitchell Bober
Sunny Annapolis (where AC stings & DC burns--or is it the other way around), MD

[rtbates]

Seraph has the isolation transformer. What I did was separate the two system grounds. Now the ONLY path for any stray AC current to follow is via the dockside cord to the supply ground. What this in affect does is eliminate any chance of an appliance AC hot wire coming loose and touching the appliance metal case and energizing the boat DC/bonding ground system. Instead it will travel down the shore power cords ground back to the AC supply ground and trip the shore breaker. Granted I must and do keep my shore power cords in tip top shape. I use a volt/ohm meter to make sure I have a good AC ground and the hot and neutral are not swapped.

You also don't want your AC ground and neutral connected at the boat either. They are connected only at the supply for the reasons mentioned above.

Basically you want any short of HOT to ground occurring in an appliance on your boat to travel OUT of the boat back to the supply.

Now IF your boat has it's own internal AC source things need to be a tad different.

Thanks for your concern.

Randy