The photograph to the right shows the interior of a residential service panelboard manufactured by General Electric. The three service conductors—two ‘hot’ lines and one neutral—can be seen coming in at the top. The neutral wire is connected to the neutral busbar to the left with all the white wires, and the two hot wires are attached to the main breaker. Below the main breaker are the two bus bars carrying the current between the main breaker and the two columns of branch circuit breakers, with each respective circuit’s red and black hot wires leading off. Three wires (hot black, neutral white, and bare ground) can be seen exiting the left side of the enclosure running directly to a NEMA 5-15 electrical receptacle with a power cord plugged into it. The incoming bare, stranded ground wire can be seen near the bottom of the neutral bus bar.
The photograph on the left shows a dual panel configuration: a main panel on the right (with front cover in place) and a subpanel on the left (with cover removed). The subpanel is fed by two large hot wires and a neutral wire running through the angled conduit near the top of the panels. This configuration appears to display three violations of the current U.S. National Electric Code: the main panel does not have a grounding conductor (here it is fed through the subpanel instead), the connection between the main and subpanel lacks a grounding conductor (it must have four wires instead of three), and the subpanel neutral bar is bonded to the ground bar (these should be separate bars after the first service disconnect, which in this case is the main panel).
An older style fuse box of the variety used in the United States
A common design of fuse box that was featured in homes built from 1940 to 1965 was the 60-amp fuse box that featured four plug fuses (i.e. Edison base) for branch circuits and one or more fuse blocks containing cartridge fuses for purposes such as major appliance circuits. After 1965, the more substantial 100 A panel with three-wire (230 V) service became common; a fuse box could have fuse blocks for the main shut-off and an electric range circuit plus a number of plug fuses (Edison base or Type S) for individual circuits.