T&T: Troubles with a GFCI shorepower plug

[2elnav at netbistro.com]

> Steve,
>
> I also have seen this problem.  I carry a 100' 115v extension cord that
> allows me to power my fridge, directly bypassing the ship's wiring.
>
> I have not had a chance to check this out on my boat, but I recently had a
> conversation with another cruiser about this problem, a gentleman who's an
> electrician in real life.  The cause my be as simple as the "Reverse
> Polarity" circuit that the good old ABYC requires us all to have.  The
> circuit is connected between the green ac ground and the white ac neutral.
> If it's a bulb with a filament, that would be enough to nuisance trip a
> GFCI   protected 115vac shore power circuit.  In addition to some places
in > Canada, we found the problem along the NY State Canal System, where
many
> docks have 115vac outlets dockside.
>
> Jim


REPLY
Jim  and Steve, now you begin to see why some of us have issues with blind
adherence to ABYC specifications.  In Europe  they  have a requirement for
a protection scheme similar to GFCI  but in this case the threshold is  30
ma  not 5 ma.
Hihj grequency switch mode power supply devices liek some chargers and
inverters  must also have a lot of bypass capacitors in their design  in
order t omet the newer  more stringent  RFI suppression  standards.  These
bypass capacitors  will each have a certain leakage current.  If you have
enough of them, the accumulated current is enough to trip a GFCI.

The sad part is,   electrical authorities recognize this and  do not
insist  on installing a GCFI directly on each dock outlet. Instead, the
electrical code  requires  one 5 ma device be installed on each outlet 
inside the boat.

Placing a 5ma  GFCI device on a 30 A dock service outlet is misguided  and
over zealous.  If such a device must be installed it has to be of the kind
 with a higher threshold.