120 VAC ABYC Code advice?

[Dan_Y]

Mainsail-
The AC circuit on our '91 H30 needs some work and I would like to get it as close to ABYC recommendations as possible. I will soon install a galvanic isolator at the boat entrance panel.

But I'm not sure what to do with the push-to-reset 30A AC breaker on the boat entrance panel that is corroding and becoming an I^2R fire hazard. I'm thinking of replacing it with a BSS two pole ECLI 30A breaker to get the whole boat protection. It seems to be an ABYC recommendation now. The main panel is about a 12-14 Ft run back to the boat entrance panel so ABYC seems to recommend placing the ECLI at the entrance panel.
http://catalog.bluesea.com/#63/z

I assume the ECLI is compatible with the galvanic isolator because the ECLI doesn't seem to trip until 30ma (I might be wrong). The GI is still a good idea if I had a small leakage to ground that was below the ECLI trip threshold of 30ma I would think.

Many thanks for your insights.
Dan

 

[mitiempo]

The ELCI and galvanic isolator do very different things and do not interfere with each other.

The ELCI is basically a whole boat GFCI that trips when there is more than 30mA difference between the hot and neutral wires - an indication of leakage within the boat's wiring system and possibly to an individual.

The galvanic isolator is there to prevent DC current from entering the boat through the earth (green) wire of the AC system. Because the AC earth and DC negative are connected on each boat any issues on any boat on the same shore power circuit you are plugged into become your problem as well. This includes your zincs (or other anodes) protecting other boats on the same circuit. The GI blocks up to 1.2 volts of DC current from entering your boat through the green wire while letting any fault in the AC above 1.2 volts reach the shore ground.

 

[Dan_Y]

Thanks mitiempo. My AC system appears to be fully isolated from the DC system - there is no AC green wire to the DC ground bus in the panel or at the engine ground, but at least the AC neutral bus is not tied to the AC green bus in the panel either. Knowing the AC green is not tied to the engine ground is why I was thinking about installing the GI and then connecting the green to the DC ground. However, currently the galvanic corrosion is really low as the zincs typically look really good when I replace them annually - but then again, none of the bronze through hulls are bonded to each other or the engine...

 

[mitiempo]

ABYC requires that the AC ground (green) wire be connected to the DC negative on board. There are safety reasons for this as the shore side ground cannot always be depended on. A fault in a device that has both AC and DC - battery charger or inverter - needs a safe path to ground. If the marina ground was faulty or non-existent the DC system could become AC hot without such a path. This connection does increase the chance of corrosion issues as all boats on the same circuit are then connected by the ground wire. A galvanic isolator both protects your boat from others stray current as well as protecting their boats from yours.

 

[Dan_Y]

Apparently tying the AC gnd to the DC negative was not required in 1991? Would you make that connection in the salon AC/DC panels by jumping the DC and AC gnd busses together? Or extend the green wire from the AC gnd bus in the salon panel to the engine DC ground lug?

 

[mitiempo]

You can make the connection behind the panel.

 

[Dan_Y]

Excellent. Thanks!