You create a 120-volt circuit by connecting a wire to one of the 120-volt legs (via a circuit breaker) and another to the return bus (the return wire is also called the neutral wire). The line wire, which carries voltage, is usually black (although it can be red), and the neutral...
Another key difference between 110 and 220 circuits is the wire size. Because 220-volt circuits carry higher current, they require 10 gauge or larger wire, whereas the normal maximum wire size in a 110-volt circuit is 12 gauge. The terminal screws in 220V plugs and outlets are accordingly l...