Why Do I Have Two Electrical Subpanels and What Do They Do?

The main circuit breaker box, often known as the main service panel, is at the heart of a home's electrical system. This is the point at which the utility company's power feed enters the residence from the meter and where all of the power is distributed to the house's different branch circuits. A primary service panel is found in every home.
A subpanel is a smaller service panel that supplies electricity to a specified area of the house or other structures on the land. It functions as a satellite circuit breaker panel with its own set of breakers. The main service panel feeds the subpanel with a double-pole 240-volt breaker, and this single feed circuit is separated into extra branch circuits at the subpanel.
Advantages of an Electrical Subpanel
Subpanels are commonly used in systems for three reasons: space, convenience, and efficiency. Subpanels are typically used to extend the wiring for several branch circuits to a specific region of a home or to a building located some distance from the main panel. A subpanel could be installed in a garage, outbuilding, or room extension. The concept is to run a single set of feeder wires from the main panel to a subpanel, where the power is separated into several branch circuits serving that particular building or portion of the house. Like the main service panel, the circuits running from the subpanel may power light circuits, outlet circuits, or appliance circuits.
The benefit is that the circuits can be operated from a more convenient place rather than having to return all the way to the main service panel, which may be quite far away. Power tools in a garage with a workshop, for example, may occasionally trip circuit breakers, and resetting them from the garage subpanel rather than the main service panel is much easier.
When the main service panel's breaker slots are full, a subpanel can be a practical option to add additional circuits. For example, you can divide 60 amps into numerous smaller circuits by wiring a single 60-amp breaker to a subpanel.
Finally, by lowering the number of "home runs" back to the main panel, a subpanel can save time and money during construction. Running three or four individual circuits from a remote place back to the main panel costs more materials and labor than running a single high-amperage circuit and dividing it into smaller circuits from the subpanel.
How is a Subpanel Connected?
Two hot wires must be connected to a 240-volt double-pole breaker in the main panel to form a subpanel. A neutral and ground wire is also required. "Three-wire cable with the ground" is the type of cable utilized for this run. The subpanel will be powered entirely by the two hot wires, known as feeder wires. This wire runs from the subpanel to a 240-volt main breaker or main lugs, which feeds power down two hot bus bars. Individual circuit breakers will be connected to these bus bars to distribute power to the subpanel's branch circuits.
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