[sailingdog]

First, just because someone is a professional, it does not mean that they are competent or know what they're doing. All it really means is that the IRS knows they get paid money for doing it.

Second, not all outlets need to be GFCIs. As long as the first outlet in the circuit is a GFCI, the entire circuit is protected by the first outlet. If the electrician installed GFCI outlets at every location, he's an idiot and spending a lot of extra money where it isn't necessary.

Third, there are some who don't like connecting the AC ground to the DC ground. However, IMHO, it really should be done. From the Blue Seas website:

Without a good connection between DC negative and AC safety ground, stray AC current may enter the DC ground system. When this happens, AC current may enter the water around a boat and injure or kill swimmers near the boat.

The green wire is the safety ground wire that connects the DC negative ground block to the AC safety ground bus. The purpose of this wire is to provide a lowest-resistance path to ground for any stray AC current that finds its way onto the DC ground system. There have been cases of AC current entering the water around a boat through the engine shaft and killing swimmers near the boat.


There is a down side to this green wire connection. This safety ground can also provide a path for galvanic current if the boat is not adequately protected with galvanic isolators. However, most marine industry organizations and professionals now consider it standard practice to install this wire. Safety requires providing the grounding wire, either directly or through a galvanic isolator, or using a properly installed marine isolation transformer. Some people have left off the ground wire in a mistaken notion that they are providing galvanic protection, but forget that they are compromising safety for those on the boat, on the dock, and in the water. Electrically induced drowning is now recognized as a previously undocumented cause of death. The Coast Guard is funding a study to isolate and investigate this hazard.


The green wire can be tested and indicate continuity but be unable to safely carry enough current to trip a circuit breaker during a fault. There are ways to check the quality of the connection.


An Ohm meter test may show very little resistance in a green wire installation, yet the wire may be incapable of carrying 30 amperes or the higher currents needed to trip a circuit breaker during a fault. The minimum resistance reading of an Ohm meter will not necessarily indicate if a connection is compromised, such as a connection making to only a single strand of wire. There are specialized ground resistance testers that apply significant current, but they are uncommon. Careful visual inspection of the grounding connections helps, but even a careful surveyor may have a hard time finding all connections and tracing the wiring path.


One way to test the green wire connection quality is to connect a spot light or other heavy 12V load, positive to the boat's battery, and the negative to the safety ground pin of the shore cord. In a properly wired boat, the safety ground pin should return to the battery negative after first connecting at the AC panel. If the light burns bright and steady, there probably is a good grounding system. This is a good check to perform if a boat has an unknown maintenance history, has been rewired, or is being repaired after damage.

Fourth, your friend really needs to get a proper marine AC shorepower panel. They're not all that expensive or difficult to install. I have recommended this one for a lot of small boat setups:


Photo courtesy of Sailorsolutions.com, click to see product there.

The reason for the double breaker is to protect the boat from having a hot 110 VAC connection when you're not expecting it. If the shore power post has reversed polarity, a single breaker setup will not interrupt the 110 AC coming in on the neutral line and a serious risk of electrocution then exists.

While many boats don't need a galvanic isolator, the double AC breaker and the AC ground to the DC ground are both NECESSARY.

Originally Posted by mitiempo

A friend with a Spencer 35 and I (CS27) were discussing whether to bond through hulls or not. The concensus seems to be not to and I agree. In our research we came across info on galvanic isolators. After some reading we found that the green ground wire of an ac system on board should be connected to the boat's negative ground - negative bus and ultimately the engine ground. His boat doesn't have this connection and neither does mine. The ac system on my boat was by all accounts professionally installed with Blue Seas ac panel and tinned marine wire etc. All ac outlets are gcfi - 3 with a 15 amp breaker for each one. The shore charger is on its own breaker. The main breaker is the familiar double to break both hot and neutral and show reverse polarity. My friends Spencer 35 has a more basic system with a household box and no main double breaker but he does have gcfi outlets. Everything that we read explains ABYC regulation of grounding the ac green and goes on to explain the need for the galvanic isolator. My question is what is wrong with not grounding the green to the engine block and using gcfi outlets. It obviously works and has for many years. In my reading it seems that by connecting ac ground to the engine block and therefore to the dc ground you are inviting more electrolysis issues. What does everybody else think of this?
Brian