We had a small electrical problem a couple weeks ago.  While making breakfast and running the air conditioner one morning, we got one of the conductors in or 220V wiring hot enough to melt through the insulation and short against the other conductor.  This caused our 50A shore power breaker to trip.  That put an abrupt end to the air conditioning, battery charging, and pancakes.

The wires in question are 8 AWG and more than adequate for carrying 50A at 110V.  I’ve seen the stove pull an impressive amount of power, but the breaker should have tripped long before any wiring was damaged.  If our breaker failed to trip for some reason, there is another 50A breaker on the dock that would have.

Where the short occurred was immediately after the transfer switch that selects between shore power and generator, and I later discovered that the switch itself would no longer turn.  Did the switch fail internally and cause the problem, or did a bad wiring connection cause the heat buildup and melt something inside the switch?  I’m betting on the latter, since I discovered some corrosion in the connection.

The switch itself is a Kraus & Naimer C42 A212 and not the kind of thing you can walk into a local store and pick up.  But I felt fortunate that the first call I made to a marine electronics shop yielded the part in inventory.  It was in my hand two days and $275 later.

Replacing the switch and burned wire was unremarkable except for the mechanical challenges of crimping 8 AWG.  Most crimpers only go down to 10 AWG.  I bought an uninsulated barrel and a crimper that could handle 8, 6, 4, and 2 AWG.  After crimping, I covered the splice with heat shrink tubing.   I did not put any type of dielectric grease on the connection,  but I’m wondering if I should have given the corrosion.

In the current setup, the boat’s 220V ammeter only measures the black conductor the circuit.  I wonder if it would be advantageous to install a second ammeter for the red conductor.