T&T: Need help troubleshooting electrical problem

[Ken Bloomfield]

Ken,

There is some info that you have left out that I am not sure of, so my guess
may be off.  The info that you left out is whether or not you plug in two 30
amp cords or not.  You speak in the singular ("my 30 amp cord"), but
normally if a boat is wired to accept either 30 amp or 50 amp service, it is
set up for two 30 amp cords or one 50 amp/125/250 VAC cord.  At any rate,
here goes:

I suspect that the 50 amp shorepower outlet is protected by a combination
GFCI/Current breaker.  That means that either overcurrent, OR a ground fault
detected can trip the breaker.  I think that there is a ground fault (minor,
but GFCI's are touchy) in that offending circuit, and my suspicion would be
the microwave.  You might wonder why if everything is off that this could
happen.  The answer could be that there may be a line filter in series with
the power input on the microwave that has a leaky capacitor therein, and
this line filter (supposed to be totally passive) may well be prior to the
actual power switch.  Put that circuit back to normal (i.e. reconnect the
neutral if still disconnected) and unplug everything you can and see if the
breaker still trips.  Then, start plugging things in one at a time and watch
for a trip.  I suspect this will nail the culprit down.

If not, then there may be a wiring fault in the wall.  In the event that
this does not nail down the culprit, get one of the really cheap polarity
testers (Lowe's, Home Depot, etc) with the 3 neon lights and ensure that
every outlet is correctly wired polarity wise.

Hope this helps,

Ken.

Ken Bloomfield
Cell# 865-293-2174
MTOA# 2062
AGLCA# 3529
M/V Tellico Lady, 50' Marine Trader-Walkaround
Maryville, TN