Re: [A/S] Ground Faults and hook ups

["Dr. Gerald N. Johnson, electrical engineer" <geraldj@xxxxxxxx>]

A properly working and wired GFCI trips when the current passed through
the hot wire is not all returned through the neutral wire. It is
possible to miswire the GFCI unit. It is more likely an indication that
a wire in your landyacht has a problem. Most likely neutral and ground
(black and green or bare) have been interchanged at some receptacle or
appliance. Or neutral and ground have been connected together by some
wiring error in the trailer at the main box or a receptacle. As likely
is a screw or nail (especially on a SOB put together with nails)
connecting the shell or frame to a wire. When either of these errors in
wiring exist, the GFCI properly trips. Its premise of safety is that if
current returns by any other path than the neutral (white) wire, it
could have returned to ground through the body of some person and the
GFCI is calibrated to trip at such a current smaller than most people
can feel. At the same time loads and circuits will function with these
wiring errors when used from a non-GFCI outlet or generator. Crossed
neutral and ground wires (as well as neutral and grounded shorted
together) are not a great safety hazard (unlike the nail through the
wire and holding on the aluminum skin) but are treated as such by the
GFCI. Energizing the shell of the trailer isn't a problem unless you
happen to touch it while standing on the ground. Then its at least very
irritating, but can kill. There should be no connection between neutral
and ground anywhere in the trailer. All loads must function with the
ground wire disconnected (this can be a hazardous test because if some
load does return through the ground, disconnecting the ground at the
source can lead to a shell energized through that load. That can be
deadly). If any fail to operate with the ground wire disconnected that
is a sign of that load (speaking ONLY of 120 volt loads) being connected
improperly. It would be safer to disconnect the neutral source wire in
the main panel and see if any loads continue to operate. Any that do in
that situation are wired improperly as the GFCI has indicated. As Phil
Piper noticed a couple days ago, mice do chew wiring insulation. Motion
of wires in a trailer can wear through insulation. Either one can lead
to shorts that were not there previously.

Its worth purchasing and carrying a three neon bulb outlet tester to
check outlets in campgrounds for proper wiring. This device will not
detect improperly shorted ground and neutral, and will not detect
accidental grounds in the ground circuit (e.g. badly made safety
connections) but it will help isolate problems to trailer or campground.

Something like the E-Z Check Plus GFI Circuit Tester will test for
proper wiring and for proper GFCI operation. My last electrical supply
catalog shows it lists for $32 but that's cheaper than a fatal shock or
a wasted visit to an electrician for checking trailer wiring. Some of
the less expensive outlet testers may trip a GFCI and make the test
difficult to complete.

Gerald J.