T&T: 120V green ground conductor

[KevinR]

> -----Original Message-----
> As for the ground, this is exactly what you need an isolator for. You should
> use a 30 amp isolation transformer, and connect the ground on the output side
> to the 12 volt ships (DC) ground. The incoming AC ground (green wire) goes to
> the input of the transformer. It's critical that the incoming AC ground is
> kept isolated from the ship's DC ground, especially on a wooden boat.

A bit of clarification here -  ABYC E-11.17 requires that the safety ground (green wire) of the
AC system ON THE BOAT be bonded to the "engine negative terminal or its bus". However, to
prevent galvanic corrosion, a galvanic isolator OR an isolation transformer is also needed.
While an isolation transformer is an excellent way to provide the isolation, they are big, heavy
and expensive. As such, the galvanic isolator that Paul proposed should be just fine for his
application.

If the boat uses a shore power system as used by many trawlers under 40' and as Paul described
(i.e., 30A, 120V, no isolation transformer, with a galvanic isolator), the green wire on the
boat side of the isolator MUST be bonded to the DC ground/engine block (see:
http://www.yandina.com/acrobats/GalvOwnManual.pdf).

An alternate way of complying with the requirements if you have the space and budget to do so,
is to add an isolation transformer to the circuit (see:
http://www.victronenergy.com/upload/documents/Datasheet-UK-Isolationtransformer.pdf). This
transformer sits between the shore power inlet and the main AC panel. The safety ground (green
wire) is galvanicly isolated from the shore safety ground, but the boat side green wire still
gets bonded to the DC ground system.

Kevin