31 August, 2023

Any DIY job can be daunting and even a little dangerous. When installing a sub panel with a main breaker, you need to keep your wits about you. Always ensure that the power is switched off at the main switch, to prevent you from being injured. 

The process of opening the main circuit breaker panel box is relatively simple. You simply need to connect 3 wires to add a circuit. As long as you follow all the safety precautions, you shouldn’t have a problem. 

What’s Inside Your Main Breaker Panel

Let’s take a look at what you will find inside your main breaker panel and how to wire a subpanel:

Main electrical lugs: These lugs are always live – which means they can shock you, even when the main breaker switch is turned off! Make sure that you never touch them at all!

Main cables: Don’t touch the black cables as they are live. Even if they are insulated, they can still shock you!

Main breaker: Ensure this is switched off at the source before removing the cover panel.

Breaker: The red or black wire is the hot wire. Each circuit connects to the breaker. You will also find the neutral wire here.

Breaker bus: Each main breaker is attached to the bus. The breaker bus distributes power from the main circuit breaker to each circuit breaker.

Neutral bus: The ground and neutral wires are connected here. The wires are usually white.

Breaker space: This is where there is space for you to add 3 more breakers. They can be installed in one of the open spaces. Take note when wiring a subpanel.

A load center helps provide safety by housing all the branch circuits in one enclosure.

Tools & Materials Required

To get the job done correctly you will need the correct tools and materials.

Tools required

  • Wire stripper/cutter
  • Flashlight
  • Utility knife
  • Needle-nose pliers
  • Pliers
  • Voltage tester

Materials required

  • Electrical staples
  • AFCI circuit breaker
  • Cable clamp

As an extra precaution, you should wear rubber-soled shoes and wear shock-resistant gloves. Before touching the circuit breaker, triple-check that the electricity has been turned off at the source,

Steps to Install the Subpanel

  1. Test the feeder wires for power
    The power will need to be turned off by your power utility company. You. or the electrician must check the feeder wires for power using a voltage tester. If there is no current, you may proceed.

  3. Open knockouts in the box
    Inside the box, you will find metal knockouts, these are the leading service conduit. This is where each branch circuit enters the breaker box. The knockouts are located at the top, bottom, sides, and back of the box. They come in various sizes to match different-sized conduits. The knockout can be opened using a screwdriver. Once they are open, the conduit or cable connectors can be installed. To secure them into place use knurled lock nuts threaded onto the tailpieces from inside the panel.

  5. Mount the circuit breaker panel
    Level the circuit breaker panel and anchor it to the wall. The holes should line up. If they don’t you may need to drill additional holes at the back of the panel so that the new installation will fit, or mount a piece of plywood to stabilize the panel.

  7. Install the main service wires
    Feed fish tape around through the main service conduit opening from the entry point outside the house where the main service wires are located. There are 3 main service wires. 2 – black hot wires, and 1- white neutral wire. The main service wires are secured to the end of the fish tape with electrical tape. These are pulled down into the breaker panel. Get a helper to push the wires from the outside, while you pull from the inside. Allow for extra wire length to add additional connections.

  9. Connect the main ground wire
    The main ground wire is a bare copper wire, and this is fed into the panel and connected to the main grounding connection. It will be connected to a grounding rod, which is connected to the grounding electrical lug in the service panel.

  11. Connect the main service neutral wire
    Connect the main service wire to the neutral bus bar in the electrical sub-panel.

  13. Connect the main breaker
    Strip the ends of the service wires with just enough insulation to connect them to the main circuit breaker terminal lugs. Ensure that the screws are tightened to the main lug panel installation.

  15. Pull wires for branch circuits
    Use fish tape to pull the various branch circuits into the panel.

  17. Connect the branch circuit ground wires
    Connect the green and bare copper wires for the branch circuits to the ground bus bar. secure in place using screws.

  19. Connect the branch circuit breakers
    Connect the circuit’s neutral wire directly to the breaker, attach the circuit hot wires (load power), and attach the breaker’s white pigtail wire to the neutral bus bar in the panel.

  21. Complete the installation
    Replace the cover, then call the utility company to restore the power. Ensure all the circuits are working correctly. Label the panel to identify the function of each circuit.

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