Q. I’m installing a simple three-wire 120-volt shore power system on my sailboat. The system will have a proper breaker/distribution panel that will feed a multi-stage marine battery charger as well as two cabin outlets (two receptacles each). My boat is outboard-powered. What can you tell me about proper grounding for the 120-volt system?

A. Your question has two areas that need some consideration. First of all, when connecting 120-volts to your alternating current (AC) distribution panel, you will want to be certain that the wires are connected correctly. “Polarity” is critical; “hot” and “neutral” shore power wires must connect to the proper terminals in the distribution panel. This is very important; otherwise, having “reverse polarity” can damage equipment or, worse, create heat or fire. The colour codes for the wires are black for hot wire; white for neutral wire; and red or green for ground wire.

Secondly, the shore power ground must be connected to the distribution panel ground.
The chassis of the charger should be attached to the ground on your AC panel. Since you are working with an outboard engine installation, all grounding will be to the 120-volt AC distribution panel. The battery ground should not in any way be connected to underwater metallic fixtures.

Anyone worried about working with electricity should consult a qualified professional.