An expanded view of house wiring is provided in [Fig. 1]
a discussion of the entire system. The house panel has been included
with the "feed" and the important grounding mechanism. In addition, a number of typical circuits found in the home have been included to provide a sense for the manner in which the total power is distributed.
Fig. 1: Home wiring diagram.
First note how the copper bars in the panel are laid out to provide both 120 V and 208 V. Between any one bar and ground is the single-phase 120-V supply. However, the bars have been arranged so that 208 V can be obtained between two vertical adjacent bars using a double-gang circuit breaker. When time permits, examine your own panel (but do not remove the cover), and note the dual circuit breaker arrangement for the 208-V supply.
For appliances such as fixtures and heaters that have a metal casing, the ground wire is connected to the metal casing to provide a direct path to ground path for a "shorting current". For outlets and such that do not have a conductive casing, the ground lead is connected to a point on the outlet that distributes to all
important points of the outlet.
Note the series arrangement between the thermostat and the heater
but the parallel arrangement between heaters on the same circuit. In
addition, note the series connection of switches to lights in the upper right corner but the parallel connection of lights and outlets.
Due to high current demand the air conditioner, heaters, and electric stove have
30-A breakers. Keep in mind that the total current does not equal the
product of the two (or 60 A) since each breaker is in a line and the same
current will flow through each breaker.
In general, you now have a surface understanding of the general
wiring in your home. You may not be a qualified, licensed electrician, but at least you should now be able to converse with some intelligence about the system.