Residential, Cook Electric
Written by Larry Cook

Basics of Home Electrical Subpanels – Part 1

The heart of every home’s electrical system is the main service panel or circuit breaker box. This is where the utility company’s electric feed enters your house from the meter. The main service panel’s job is to distribute electricity to the branch circuits of a home.

An electrical sub-panel works like a smaller service panel with its own circuit breakers, distributing power to an area of the home or a nearby structure. A subpanel is installed in an accessible place for the area it services.  

Why Subpanels Are Necessary

Some homes require subpanels to add circuits to a location located far from the main service. Subpanels are often necessary for a guest house or garage on the property. Typically rated at 60 to 125 amps, a subpanel’s capacity will be determined by the anticipated electrical usage of its service area.

Additional circuits will be split off from a sub-panel to supply power to car chargers and large appliances to meet their power demands. Every electrical subpanel located on a detached dwelling will require a grounding system of its own.

Subpanel Connections

An electrical sub-panel requires two hot wires connected to a 240-volt double-pole breaker within the main service panel. Moreover, a neutral wire and a ground wire will be needed. This wiring configuration is called a “three-wire cable with ground.” Functioning as feeder wires, the two hot wires supply all the electricity to the sub-panel.

A three-wire cable with the ground is connected to a 240-volt main breaker within a sub panel, providing electricity to two hot bus bars. Connected to the bus bars, circuit breakers distribute power to the branch circuits running from a subpanel.

Subpanel Sizing

Properly sizing subpanels to meet the expected electrical load presents a few challenges. The two factors are the capacity of the main service panel and the amount of available power load required.

For example, a home equipped with a 200-amp main service panel will have no problem installing a 100-amp subpanel to provide electricity to a barn, garage, or shed. It should also have no issue supplying a 60-amp subpanel for lighting a newly added room or powering general-use outlets.

Part 2 will cover Electrical Subpanel Benefits and Savings During Construction.

Electrical Peace of Mind

Providing professional electricians since 1988 in Maryland, Cook Electric is the company you can rely on for all your electrical service needs. For knowledgeable, fair, honest, reliable, and conscientious service, call Cook Electric today at (410) 266-9040. We will be very glad to help you.