Inside Your Main Electrical Service Panel, do you know it?
When you open the panel door, you gain access to the circuit breaker switches, but that's all. And that's as far as most homeowners need to go. However, to get inside the panel to install or replace a circuit breaker, you have to remove the protective cover around the breaker switches, known as the dead front cover. The dead front cover is typically held in place with a screw in each corner. Removing the cover provides access to all components of the panel. Some panels have a separate door and cover; others have a door and cover as parts of the same unit.
1. Main Circuit Breaker
The main circuit breaker is a large breaker usually located at the top of the panel but sometimes near the bottom or along one side. It controls all the power of the branch circuit breakers (the breakers controlling individual circuits) in the panel.
Power comes from the utility service lines, flows through the electrical meter on the outside of your house, and continues into the service panel. However, some systems include a separate disconnect switch between the meter and the panel. The main breaker is used to turn power to all the branch circuits ON or OFF at the same time.
The main circuit breaker also identifies the total amperage capacity of the service panel and will have a number on it identifying its amp capacity, such as 100, 150, or 200. The standard for new panels today is 200 amps, but panels can have an even higher capacity.
2. Neutral Bus Bar
Once the power leaves the electrical service panel through the hot wire(s) of a circuit and does its work through the electrical devices (light bulbs, outlets, etc.), the electrical current returns back to the service panel through the neutral (usually white) circuit wire, which is connected to the neutral bus bar. The bar connects to the main service neutral and returns the current back to the electric utility grid.
In many service panels, the neutral bus bar also serves as the grounding bus bar and is where the individual bare copper circuit ground wires are terminated. In this case, it is often referred to as a neutral/ground bus bar.
3. Main Bonding Jumper
The main bonding jumper provides a ground connection between the neutral/ground bus and the service panel. Another ground connection is made by the grounding electrode conductor or GEC. This is a bare copper wire that connects the neutral/ground bus bar to a ground rod driven into the earth near the service panel or to metal rebar in the home's foundation. This final ground connection with the earth allows stray electrical current (such as a surge created by lightning) to pass safely into the surrounding soil.
4. Ground Bus Bar
Some service panels have a separate bus bar for ground-wire connections, instead of a neutral/ground bus. In this case, the ground bus is electrically connected to the neutral bus in main service panels only; in subpanels, the ground bus and neutral bus are not connected to each other.
Above some information about the inside your main electrical service panel, hope it will be helpful for your using the panel box.