A 100-amp main breaker panel receives 100-amp service at 240 volts. Electricity enters the home via the meter socket and service-entrance wire. Two-gauge, three-conductor aluminum SER wire is an appropriate 100-amp service-entrance wire. The service-entrance wire runs from the meter socket outdoors to the main breaker panel indoors, delivering the 100 amps of electricity.
The two black insulated conductors of the service-entrance wire connect to the main lugs on the breaker panel. A 100-amp double pole main breaker limits the amount of electricity coming in from outside. When this main breaker is on, electricity flows to the bus bar of the main breaker panel and is allowed to flow through each branch circuit breaker to individual branch circuits. The neutral conductor of the service-entrance wire connects to the neutral bus bar in the main breaker panel. The neutral bus bar is the connection point for all white neutral wires, which return electricity to the panel after it flows through each branch circuit. The grounding bus bar in the main panel unites all grounding wires from individual branch circuits. In a main breaker panel, the neutral bus bar and grounding bus bar are connected via a bonding strap. The grounding bus bar also connects to a grounding conductor or rod that is located outside of the residence. Electrical service work should always be conducted by a licensed, professional electrician.