Working at a house the other day, I came across a 30-year old Zinsco subpanel in a garage with serious corrosion problems. The panel is a 100A MLO, located next to a clothes dryer which was vented to the garage for 20 years or more.
The breakers were frozen in place. I presuaded them out, and the 30A water heater and 40A water pump breaker clips and corresponding busses were very badly pitted. The area behind the water heater breaker was badly scorched.
I cleaned up the busses and clips with a scotchbrite pad and some Noalox, wiped the busses and clips clean, and applied a thin coating of Noalox. I rearranged the position of the breakers so that a spare breaker sits on the most badly pitter section of buss, and a lightly-used 15A convenience outlet breaker on the next worst pitted section.
The circuits all tested OK (voltage and voltage drop, using an Ideal Sure-Test). When I put the panel cover on, I had to move the breakers around a bit to center them in the opening (as usual). The circuit served by the 15A breaker sititng on the bad section of buss read 80 volts. With te panel cover off, the voltage at the breaker terminal was O.K. (124V). With cover back on, circuit voltage was 80 again. All other circuits were O.K.
I left the situation with the cover on but with a slight mis-alignment of the breakers in the opening. There is a door over the area, so the 1/8" or less gap is not exposed unless the panel door is open.
The house is going to be remodeled starting a month or two, and this panel will be replaced, probably within 4-6 months. Any suggestions on how to better deal with the situation?
I'm thinking that if the poor contact between buss and breaker clip becomes a problem, I'll buy some of that Ilsco silver paste (used for improving connections between bolted buss bars), expecting that it'll improve the contact between the buss and breaker. I'd rather not double up the circuit with another. Any comments or other ideas?
If the problem is just on the one lightly loaded circuit, I'd rather double up via pigtail splice to another lightly loaded circuit. The poor contact between the breaker and bus may cause problems under load, even if it seems ok now. And I wouldn't rely on the owners promise of changing the panel in the future. Too many things can happen in the meantime.
BTW, is there a such thing as a "good" Zinsco panel?