The Breaker Box is the entry point into the residence from the power company. The box is typically metal and usually has a hinged door that opens to reveal Circuit Breakers for Main entry and individual circuits. In older American homes 100 amp service is common. Homes built in the last two decades often have 200 amp service. As new homes today grow ever larger, service greater than 200 amps may be used. You can see the amp rating of your electric service by opening the Breaker Box door and looking for the large circuit breaker near the top of the panel. This is typical at the top, centered and marked "MAIN." Numbers will appear on the lever of the Main Breakers. The Main Breakers may have two levers side-by-side joined by a strip of metal (so one cannot be thrown without the other). If each of the two levers have "50" on them, you have 100 amp service, two "100" and you have 200 amp service.
Breaker Box - ganged 100amp breakers: top right
In a correctly functioning Breaker Box, moving the Main Breaker to the "off" position turns of electricity to all circuits in the box. Behind the front panel of the Breaker Box, electricity is still on at the points where it enters from the Power Meter. The front Panel of the Breaker Box should not be removed except by a qualified, licenced elecrician. Even with the Main Breaker OFF, the inside of the box is extremely dangerous. Entry or probing into the box can result in death by electrocution.
With the panel remaining in place and the door of the Breaker Box open, individual Circuit Breakers will be seen in two columns. They are typically numbered with odd numbers on one side and even numbers on the other.
Behind the panel that you should not remove are electric feeders from the Service Entry Meter connected to two flat metal bars. These vertical bars provide a snap connection and bring current into the circuit breakers. Black and red wires from the circuits are connected directly to circuit breakers.
Also within the Breaker Box is a Ground Bus. This is a metal bar where all ground wires and white wires from the circuits are connected. The Ground Bus is grounded by a copper cable connected to either a metal pipe for the cold water supply system or a heavy copper rod driven into the earth. The type of ground system varies depending on local electrical codes.
