Lee Huddleston wrote:
I have a 2 pole 30 amp breaker on my boat. I installed it because
Nigel Calder recommended it in this book.

I don't get it. What's all this talk about GFCI on a boat with an
isolation transformer? Beyond the transformer, there is no physical
connection to any shoreside wiring, the boat's AC circuits are
isolated.

Aren't isolation transformers set up this way --

Shoreside hot and neutral wires connected to isolation transfomer input
windings. Ground wire connected to isolation transformer shield, to
protect against transformer failure. Ship's hot and neutral wires
connected to isolation transformer output windings. No AC ground wire
in ship's wiring. No connection of any AC wires to any DC wiring. No
risk of stray DC currents generated by the ship's AC wiring anywhere.
Only risk is touching the ship's hot and neutral wires simultaneously,
which is the same risk as with any AC wiring.

That being said, I also have a 2 pole 30A breaker on the shoreside of
the isolation transformer, per Calder, in case the dock breaker is
faulty.