Calm down Bruce. His question was about DC power systems, not the fine
points of "grounding" HF antenna systems.

My point was the DC power system does not require a "connection" to the
water like lightning systems or HF radio systems normally do.

"Sec. 120.378 Ungrounded systems" is talking about isolated, from ground,
power systems on commercial vessels. I believe, from a quick search, that
section is referring to inspected small passenger vessels that carry more
than 150 passengers. In any case they are not talking about a DC power
system on an 'uninspected' non-commercial wood hulled 40 foot catamaran.

Besides, the connection point for the negative battery cables and the
negative leads from the lights, etc. IS the boats ground point. So the
system is 'grounded' even if there is nothing else, like an engine, to
connect to it.. If you added a second, completely separate, electrical
system, and didn't connect it to this 'ground' point, then that would be an
'ungrounded' system. However, I have no idea why you would want to do this
on your boat.

A "Ground Detection System" is used to monitor an isolated, non-grounded,
electrical system where there would be danger to people or other equipment
if a portion of the ungrounded system was accidentally grounded. Such as,
exposed current carrying conductors could then present a shock hazard. I
have seen systems like this for aluminum smelting pot lines and nuclear
waste vitrification furnaces. I don't think you need one on your catamaran.

"Polarizing ground" generally refers to the ground applied to one leg of the
secondary winding of an AC transformer. This is how a "Neutral" leg is
created for a 'separately derived' AC power system. Again, this doesn't
apply for a simple DC power system on a wood hulled 40 foot catamaran.

Rusty O