On 2005-02-25 12:44:20 +1100, chuck said:

Hello Eric,

Thanks for clarifying.

I believe you are correct. You are talking about high-resistance
onboard leakages that generate currents too small to be detected by the
GFI circuit or the breakers. The isolator diodes would probably not
conduct under those circumstances and a capacitor would help.

UL requires the GFI to trip at a 5 ma unbalance, so 24,000 ohms of
leakage would trip it. Actually, the isolator diodes would probably
pass 5 ma in that circuit without a capacitor. The capacitor would be
necessary when the leakage resistance was in the megohms and the
currents in the microamps.

Would rather not have that stuff flowing through my ground connections
through the water to adjacent boats, even at those low current levels.
This underscores the importance of making sure you don't have dangerous
leakages onboard in the first place. Easy enough to check, but how many
regularly test their GFIs?

We sure agree on the isolation transformer, too.

Thanks again, Eric.

Chuck

Chuck,

I am puzzled by your UL 5 ma rating.

Here in Australia we have basically two ratings. The first is for most
domestic installations an is 30 ma. The second is for hazerdous
locations including hospitals where the rating is 10 ma. There are
other higher rating RCD (Residual Current Devices) which are used in
industrial contexts (eg 60 ma) but the majority of installations are
either 30 ma. or 10 ma.

BTW I am an EE as well as a licensed Electrical Contractor.

--
Regards,
John Proctor VK3JP, VKV6789
S/V Chagall