Weird Home Circuit Breaker Problem?

These pictures are for aluminum wiring that is something like 50 times more likely to create problems compared to copper. But many pictures also demonstrate how to make conventional copper wire splices. First, all wires must be twisted together to make good electrical connections without the wire nut as in pictures 40 and 41:

in picture 42: nut (properly sized for the number of wires) screws onto that wire assembly in picture 45. Picture 48 demonstrates what happens long term if the wire nut assembly is not properly constructed. This web site is for aluminum wires. For copper wire, anti-oxidant (the inhibitor) is not required. Copper is far more forgiving. But the failure created by bad aluminum wire splices demonstrates why four wires should be electrically and mechanically solid before a wire nut is even attached. No wire junction should be dependent on the wire nut alone to hold that connection together.

Picture 50 through 54 demonstrate a worst case failure mode. Obviously most never experience anything so dangerous. But it demonstrates, again, why properly twisting wires before applying wire nut is important (as well as demonstrate why aluminum wire is that much more dangerous). All wires must make solid and multiple contacts with the other wires. Then a wire inside the wire nut, furthermore, bonds all those wires together. Picture 50 through 54 show consequences of not making good wire splices before applying the wire nut:

Steven Banks wrote: