I've been doing some reading in preparation for a small shore power installation. It's clear that I should connect the AC ground (green) to the DC negative (consistent practice, from ABYC specs, Nigel Calder, @Maine Sail's posts at AC-DC ground, and other reliable sources).
And it's clear that I should make that connection on the boat side of the galvanic isolator - yes, I read Testing A Galvanic Isolator and found a fail-safe isolator (and no, I couldn't quite spring for an isolation transformer).
So far as I can tell, that ground -> DC negative connection would often be at the engine block. But it's unclear to me where to do that in a boat without an inboard. Should I use:
1) The boat side of the battery meter shunt (where all other DC negative connections come together)
2) A negative battery terminal (breaking the rule that all connections go through the shunt, but in theory this one shouldn't be carrying current, so perhaps a direct-to-the-battery connection is better?)
3) The negative bus nearest the shore-power inlet
Pro: within a couple feet of the inlet, galvanic isolator, and AC panel
Cons: An extra 10' or so from the battery bank (on AWG 2 cable); connects to the boat side of the shunt (so similar to #1, but with an extra 10' or so of (heavy-gauge) wire in between).
4) Some other location I'm not thinking of
How heavy should that AC ground -> DC negative connection be? 10 AWG (sufficient for the 30A shore-power current)? Or is there some reason it would need a heavier cable?
And it's clear that I should make that connection on the boat side of the galvanic isolator - yes, I read Testing A Galvanic Isolator and found a fail-safe isolator (and no, I couldn't quite spring for an isolation transformer).
So far as I can tell, that ground -> DC negative connection would often be at the engine block. But it's unclear to me where to do that in a boat without an inboard. Should I use:
1) The boat side of the battery meter shunt (where all other DC negative connections come together)
2) A negative battery terminal (breaking the rule that all connections go through the shunt, but in theory this one shouldn't be carrying current, so perhaps a direct-to-the-battery connection is better?)
3) The negative bus nearest the shore-power inlet
Pro: within a couple feet of the inlet, galvanic isolator, and AC panel
Cons: An extra 10' or so from the battery bank (on AWG 2 cable); connects to the boat side of the shunt (so similar to #1, but with an extra 10' or so of (heavy-gauge) wire in between).
4) Some other location I'm not thinking of
How heavy should that AC ground -> DC negative connection be? 10 AWG (sufficient for the 30A shore-power current)? Or is there some reason it would need a heavier cable?