When it comes to finishing your home, you’ll definitely want electrical power in the following rooms:

  • Garage
  • Finished basement
  • Home theater
  • Home office
  • Shed/workshop

If your main circuit breaker can’t take on the extra load, then you can install an electrical subpanel to divide the power and provide electricity to the new area of the house. It’s always easiest and safest to have a professional electrician install a new subpanel, but it is possible to try it yourself.

If you’re in the DIY mood, follow this guide to learn how to wire a sub-panel.

To Start: Tips, Tricks, and a Glossary

Unless you’re a trained electrician, you’re going to see lots of new words that might feel overwhelming! To perform this project, you’ll need to set aside a couple of hours and plenty of patience. Let’s start by going over some definitions, as well as universal tips for installing a sub-panel.

Terms You’ll Need to Know:

  • Amps: Short for “ampere,” amps are the standard unit of measurement in electricity.
  • 4-wire feeder cable: This cable should be included with the subpanel, and it features four wires inside— black and red wires (hot wires), white wire (neutral wire), and bare metal wire (ground wire).
  • Bus bar: A metal strip that connects wires to power the electrical panel. There are neutral, ground, and hot bus bars in a sub-panel.
  • Feeder breaker: A black cube with switches on it that gets added to the main panel to feed power to the sub-panel.

Universal Tips:

  • Install the wires in clean, neat paths around the perimeter of the sub-panel. Unorderly wires can create a fire hazard.
  • Install the subpanel at least 1 foot away from the main panel.
  • Don’t purchase or install used panels or cables.
  • Never install subpanels in bathrooms or closets. Otherwise, they could get wet or overheat, ultimately causing a fire hazard.

Tools & Supplies You’ll Need:

  • Screwdriver or power drill
  • Hammer
  • Voltage tester
  • Subpanel
  • Mounting screws
  • Feeder cable
  • Cable clamps (or staples)
  • Feeder breaker
  • Flashlight or portable lamp
  • Wire strippers
  • Long-nose pliers

Step 1: Consult With a Home Inspector

how to install a subpanel consult with a professional

You don’t want to put too much strain on your electrical system by accidentally installing a subpanel with too many amps. A licensed inspector can:

  • Let you know if it’s safe to install a subpanel
  • Recommend the amperage for the subpanel
  • Issue a permit for the installation
  • Inspect the panel after installation to ensure it’s up to code

Once you know how many amps your home can support, you can purchase an appropriate subpanel from a local hardware store. The panel should come with the necessary connections. Be sure to pick up the required wall attachments if they aren’t included with the panel.

Step 2: Mount the New Panel, But Don’t Wire It Yet

Install the sub-panel near the main service panel, but make sure there’s at least 1 foot of distance between the two.

⚠️ Turn off the power to the main panel. ⚠️ Forgetting to do so can cause you to electrocute yourself.

When you turn off the main service panel, all your lights and electric devices will shut off. Use a flashlight or portable lamp (or two or three) to provide light while you work.

Then, install the new subpanel:

  • Locate a wall stud.
  • Mark where the screws need to be added with a pencil (Place the panel roughly 5 feet off the ground).
  • Drill the mounting screws into the wall stud with a power drill or screwdriver. Leave a small gap between the screw and the wall.
  • Place the subpanel over the mounting screws, then tighten the screws so that the panel fights securely to the wall.

Step 3: Connect the Wires

Feeling calm and patient? Then you can get started with the wiring. It can feel overwhelming to look at a system and wires you’ve never dealt with before. Thankfully, connecting wires isn’t terribly complex; it just requires a careful hand and time to double-check your work.

      • First, use a hammer to remove the knockout slug on the side of the panel. A perforated circle on the side, top, or bottom of the panel signifies the slug.
      • When the knockout slug is removed, insert the metal connector into the hole so you can insert the 4-wire feeder cable through it. Tighten the screws on top of the connector with a drill or screwdriver.
      • Run the feeder cable from the main service panel to the sub-panel. Keep the doors open on both panels.
      • Slide the cable out of the knockout opening on the main panel and through the knockout opening in the sub-panel.
      • Unwrap the insulation around the cable to expose the four wires inside. If the end of the wire is covered, use a wire stripper to remove about 1 inch of the sheathing.

Still with us? Now, you’ll move on to connecting the wires from the 4-wire feeder cable to the appropriate places in both the main panel and the sub-panel. The inside of the door on your main circuit breaker may have a diagram that shows the location of all the bus bars.

      • Insert the white neutral wire beneath the screw at the top of the neutral bus bar on the main panel, then secure it by tightening the screw. Connect the other end with the same steps in the subpanel.
      • Next, connect the ground wire (the bare wire) to the ground bus bar on the main panel and tighten the screw. Connect the other end to the ground bus bar in the subpanel.

Now, wrapping up with the two hot wires— the red and black wires.

      • With the ends of the black and red wires stripped, insert the wires into the slots on the feeder breaker beneath the two screws on top. Tighten the screws to secure the wires.
      • Snap the feeder breaker into any empty slot in the main panel. It will click into place if installed correctly.
      • Attach the other end of the red and black wires to the two hot bus bars in the sub-panel. Insert them beneath the two screws at the top of the bus bars, then tighten the screws.

Step 4: Power Everything Back On!

You’re probably tired of working in the glow of a flashlight at this point, and now you’re ready to reap the reward of your hard work. When all the wires are secured into place, you can turn the main breaker back on. Then, turn on the feeder breaker that you just added by flipping on the switch.

If everything was installed correctly, your sub-panel should be functioning! But if you turn your main electrical panel back on and your lights or other electronics won’t turn back on, double-check your work.

If you can’t find the source of the issue, call a professional electrician to help.

Overwhelmed By This Task? Call Electric City Instead!

While it’s possible to wire a subpanel by yourself, most homeowners don’t want to risk this complicated task. A licensed electrician like Electric City Corporation can finish this project quickly, efficiently, and safely. Plus, we’ll secure permits and ensure everything’s up to code.
Call Electric City today for a free consultation about an electrical subpanel!