In essence, an electrical subpanel can be thought of as a mini service panel. Its basic structure is the same as a service panel, with a main feeder wire leading into bus bars and circuit breakers. Branch wire circuits lead off of the circuit breakers into various parts of the house.
A typical amperage and voltage for a sub-panel might be 30 amp, 240 volt.
Note that a circuit breaker subpanel does not provide additional electricity to the house; it is feeding off of the main service panel.
There are 2 major reasons why you might want to install a circuit breaker subpanel:
- If the main service panel does not have enough space to hold circuit breakers for the new circuits that you intend to install. The circuit breaker subpanel can, in a sense, create new space for circuit breakers, but in a physically separate location.
- For the sake of clarity and separation of service. Usually, a circuit breaker subpanel will service one separate area that has a discrete function, such as a kitchen, shop, office, or addition. By installing a circuit breaker subpanel, you make it clear which circuit breakers and branch circuits apply to which parts of the house. It is easy to segregate the duties of all of the branch circuits by keeping them sequestered within the circuit breaker subpanel area.