How to Extend an Electrical Panel
An electrical panel can be extended by installing a secondary or sub-panel to expand the electrical services of the main panel without overloading the circuits. Sub-panels come in a variety of sizes, allowing you to add as many as 20 breakers that will be supplied with 220 volts of current. Because high electrical current is involved, safety precautions should be followed, and you should not complete this project unless you have electrical experience.
Prepare the Electrical Panel
Ask your local utility company to shut off the power to the main service panel from the street.
Find the exact location that you plan on installing the sub-panel. Use a measuring tape to find the location 48 inches above the wall and place a mark with a pencil on the closest wall stud.
Create a 3/4-inch opening in the top plate of the wall’s 2-by-4 with a drill so the electrical cable can go into the attic and be fed to the main panel.
Hold the bottom of the sub-panel against the mark you drew on the stud and position the panel box between the wall studs. Secure the panel box to the wall by inserting the screws into the holes.
Shut off the power for the main power panel. Flip the breaker labeled “main breaker” so it is in the “off” position. Remove the screws holding the front panel with a screwdriver.
Set the voltage tester leads on the terminals on the main power line, where it goes into the main panel from outside. If the lights do not come on, then the power is completely off.
Installing the Electrical Panel
Push the electrical tape into the hole in the sub-panel and through the openings in the top plate in the wall and into the attic. Feed the tape into the attic and over the wiring in the main panel. Insert the tape into the hole in the main panel.
Connect one end of the electrical wire to one end end of the fish tape with electrical tape. Ask a helper to feed the cable to you. Pull it through the openings and into the sub-panel; use the fish tape to guide you.
Slowly feed about 1.5 feet of the cable into the sub-panel and remove the electrical fish tape. Measure out about 1.5 feet of cable for the main panel; use lineman’s cutters to remove any excess.
Trim 10 inches of insulation with a utility knife from each end of the cable, which will reveal three wires and copper ground wire. Remove 1 inch of insulation from each end of the insulated wires.Attach the wiring in the main service panel to an unused 220-volt circuit breaker. Push bare ends of the black and red wires beneath the screws on the breaker and tighten them. Position the bare end of the white wire beneath the screw on the neutral bus strip and tighten it. Secure the screw on the bare copper ground wire on the ground strip at the base of the panel.Secure the wiring in the sub-panel to the main breaker. Position the stripped ends of the black and red wires beneath each screw in the breaker and secure the screws by tightening them. Feed the end of the white wire beneath a screw on the neutral bus strip and the bare copper wire beneath a screw on the ground strip. Secure and tighten the screws.
Tighten the screws to secure the main panel with a screwdriver.
Call the utility company and ask them to turn the power back on from the street. Turn the main breakers to the main service panel and sub-panel so they are on.
- Enlist the help of an assistant to feed or pull the electrical cable so kinks do not form and damage the wiring installation process.
- You should consult your local municipality on any local building codes to see whether you need any permits before beginning the project or are required to have the work inspected after it is completed.
- Always make sure the power has been turned off before you begin working to prevent contact with high voltage, which could result in serious injury or death.