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How to Wire a 100 Amp Breaker Box – 6 Quick & Simple Steps

Written by Edwin Jones / Fact checked by Andrew Wright

how to wire a 100 amp breaker box

Unknowing homeowners without any background in electrical engineering may have difficulties when it comes to everything related to a breaker. Particularly, learning how to wire a 100 amp breaker box may prove challenging to them.

If you need to know the general 100 amp electrical panel wiring diagram, 100 amp breaker box diagram, or perhaps the specific 100 amp breaker wire size, then you came to the right place.

Wiring a 100 amp panel may seem complicated — but you have my assurance that it could be as easy as counting from one to three, given that you follow through this guide attentively.


Step-by-Step Guide on Wiring a 100 Amp Breaker Box


Tools You’ll Need for This Task

In order for you to safely and effectively wire your breaker box, it is essential that you have in your possession these following tools:

  • Electric safety gloves
  • Safety glasses
  • Screwdriver
  • Screws
  • Breaker box
  • Flashlight, in case you’re operating in a dark place
  • Wire strippers
  • Wrench

I highly recommend that you have all these tools by your side by the time you start working on your 100 amp breaker box. These tools will ensure that your task of wiring a breaker box will be safe, seamless, and easy.


Step 1. Turn off the power before starting the installation

Before proceeding with this electrical project, it is imperative that you first turn off the power before proceeding to work on the breaker box. This is a great safety precaution, as you don’t want to get accidentally electrocuted while you’re working on the circuit maintenance.

Step 2. Install the breaker box


It is a good practice to check your 100-amp breaker box for any external damage before you install it on your wall. This way, you can see if there are any disfigurements that may compromise your home’s safety.

Now, to install the breaker box, carefully attach it to the part of the wall where your meter’s electrical wires are. You can anchor it to the wall by screwing the panel’s stud to the wall itself. Ensure that all the fittings are properly attached to prevent any accidents involving your breaker box in the future.

Step 3. Installing the wires


After attaching the breaker box onto the wall, it’s now time to feed the meter box’s wires into the breaker panels. Using your wire strippers, remove an inch of insulation from the ends of each cable that you’d connect to the breaker panels. After that, insert the exposed tips of the two hot wires into the main breaker’s lugs.

Following that, insert the ground wire’s end into the neutral bus’s lug. Now, using your wrench, tightly screw the said cables to their respective lugs securely.

However, for you to be familiar with your breaker box’s wiring layout, I recommend that you refer to your 100 amp breaker box wiring diagram for more information. For example, the guide for a Square D load center can be found here.

And before I forget, the size wire you’re working with typically ranges between 2 – 4 American Wire Gauge, so keep that in mind.

Step 4. Inserting the wires into respective circuits


After carefully doing all of the steps above, it’s now time to insert the black wire from the first 120-volt circuit into the 120-volt breaker for that circuit. To be clear, this wire will be inserted into a slot beneath the screw on the breaker — do remember that.

Next up, insert the white and bare wires beneath one of the screws along the neutral bus. Like with how you secured the wires above, you should also securely tighten each of these screws with your screwdriver.

Step 5. Clipping each individual breaker


Congratulations! You made it this far through the guide. Don’t worry, you’re about to finish up, so keep on reading below.

Carefully attach the 120-volt breaker to the power bus in the breaker box’s center bar. Install the rest of your 120-volt circuits in the same manner into the breaker panel.

However, if you have 240-volt circuits, rather than only connecting one wire to the center bar, you’ll install two wires instead. Particularly, the wires will be colored black and red. Connect the 240V breakers to the panel the same way you connect 120-volt breakers.

Now, when you connect the 240V breaker to the panel, it will clip onto both sides of the power bus rather than just one, as is the case with 120-volt breakers.

Step 6. Finishing up

After doing all of the steps above, now is the time to install the breaker panel cover. Using a screwdriver, connect the lid to the breaker box using the screws included with the box. Don’t forget to fill in the index on the breaker panel door with the circuit details of each breaker circuit you just added. At this point, you can restore the electricity.


How to wire a 100 amp breaker box is a question that may plague homeowners. Understandably, each one of us wants to be familiar with every electrical maintenance task that can be easily done at home.

In order to help you in wiring a breaker box, I have curated this easy-to-follow guide so that you can easily install wirings to your circuit breakers.

I hope you have learned from this article. If there’s something unclear, or you have any questions about this guide, then you may want to drop your queries in the comment section down below.

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