Name:   MrHodja - Subject:   Household electrical voltages Date:   11/2/2016 4:15:02 PM

Plus and minus is a misnomer of sorts.  Three wires come in to a residence.  One is neutral, or ground.  The other two are 110 volts on either side of ground, thus the + and -.  Could just as easily be termed above and below.  If you look at a service panel backplane you will see that it is arranged so breaker lugs alternate between the two 110s, and a 220 breaker rests on two adjacent lugs, producing a 220 volt potential difference.  Also, 220 is wired diferently, having two "hot" wires, connected to the breaker, one to each lug, plus ground, where a 110 has one hot, one neutral, and ground with the neutral and ground connected to the same bus at the service panel.