How to Connect a Ground Wire to a Circuit Breaker

repairman working on a breaker box
What You'll Need
Insulated screwdriver
New circuit breaker
Wire strippers
Voltage tester

If you’re putting in a new circuit breaker, you need to be very sure about where the wires go, especially the ground wire. Without this knowledge, you’re not going to carry out the task correctly and the consequences could be disastrous. Connecting a ground wire to a circuit breaker is not a difficult job, but you do need to administer care and attention to be entirely safe.

Step 1 - Prepare the Breaker Box

Before you can run a wire to a new circuit breaker, you need to have sufficient room in the breaker box. As long as you do, you can turn off the power at the main breaker before beginning the task.

Take the cover off the breaker box. Place one probe of a voltage tester against the neutral bus bar and the other probe against the bus for the terminals. If you register any voltage at all, the current is still on and you should check that the power is off at the house mains.

At the side of the breaker box, you’ll see a small indented circle. You’ll need to remove this to run the wires in for the new circuit breaker. With a hammer and an insulated screwdriver, knock out the circle. If it’s a single-pole breaker, there will only be one hole while a double-pole breaker uses two holes. You can now run the wire into the breaker box.

Step 2 - Connect the Wires

preparing wires

Where you connect the wires depends on the number of wires you have to connect. In all cases, however, the ground wire will connect to a bar; which bar will depend on the age of the breaker box.

With three-wires installation, one wire will be green, one will be white, and the last will be black. The green wire is the ground wire. You will need to strip the insulation off the end of the wires and separate them so they can reach their separate locations in the breaker box.

If you have a two-wire cable plus a ground wire, you’ll need to connect the white wire to the neutral bus bar. The black wire, often referred to as the hot wire, connects to the breaker.

With a three wire cable plus a ground wire, the black and red wires both connect to the circuit breaker with the white wire going to the neutral bus bar.

In a double-pole breaker with a circuit of 240 volts, you’ll have a two-wire cable plus a ground wire. The black and white wires both go to the breaker and each will have its own screw. It makes no difference which screw you use, although you should tape the white screw with black tape to show it’s hot.

Step 3 - Ground Wire

Inside the breaker box you’ll see a bar across the box with a series of holes and screws. In most breakers boxes, there will be two of these with one for the white neutral wires and one for the green ground wires. Screw the bare end of the ground wire to this bar, which is known as the ground bus bar.

Older boxes don’t have separate bars for ground and neutral. If this is the case with your box, you can attach neutral and ground wires to the same bar.