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Project Difficulty:
Difficult
Estimated
Project Time: 30 minutes
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| Tools and Materials: |
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Circuit breaker (of the same brand as your panel and of the amperage and type--120 or 240 volts--required by your project)
Plywood or rubber mat
Safety goggles
Insulated flashlight
Hammer
Insulated screwdriver
Voltage tester
Insulated cable stripper
Insulated wire strippers
Cable connector
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Installing a new circuit breaker is as simple (and as dangerous) as replacing one. However, have an electrician make the power connections if you're not absolutely sure of the procedure. Also check your local building codes to make sure you don't need a permit and/or inspection to add a line to your home. If you're working where it will be too dark to rely on natural light when you turn off the power, have an insulated flashlight nearby.
When working with the service panel, take these safety precautions:
* If the service panel is rusty or has blackened/burned areas, don't touch it; call an electrician
* Wear safety goggles
* Stand on a rubber mat or a dry piece of plywood. Never work with electricity while standing on a damp or wet floor or earth.
* If possible, work with one hand to avoid becoming a closed path for the electrical current
* Always use insulated tools
The following guidelines are for working with nonmetallic cable.
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1.
Turn Off the Power
Turn the power off at the main breaker. Carefully remove the cover, and then check the voltage with a voltage tester to make sure it's really off. Using a voltage tester, which you can buy or rent inexpensively, could save your life.
Caution: Never touch the main lugs attached to the main breaker; that area of the panel is always hot.
To confirm that the rest of the panel is off, place one probe of the voltage tester against the neutral bus bar and the other probe against the bus to which the breakers are connected. If the voltage tester registers anything, the power still is on. Turn it off.
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2.
Remove the Knockouts
Once the power is off, and the cover taken off of the service panel box, remove a knockout in the cover to make room for the new breaker. A single-pole breaker will use one space in the box, and a double-pole breaker will use two spaces.
On the side of the service panel box, use an insulated screwdriver and hammer to remove one of the circular knockouts so that the cable may be connected properly.
Install an appropriate cable connector, and allow enough free cable to snake around the inside perimeter of box until all wires can reach their connection points. (Fig. 1)
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3.
Strip the Cable Insulation
Using an insulated cable stripper, strip the outer cable insulation immediately after it enters the panel box and snake the separate wires to their respective locations (see steps below). Use insulated wire strippers to remove enough insulation from the ends of the individual wires in the cable to make attachments.
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4.
Connect the Ground Wire
Run the cable's ground wire to the ground bus bar.
Note: Older systems may not have separate neutral and ground bus bars. If the existing system has both white and ground wires on the same bus bar, then continue adding both white and ground wires to the same bus bar. If, however, you see white and ground wires attached to separate bus bars (neutral and ground bus bars), then continue to do so for new connections.
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5.
Connect the Wire(s) to the Circuit Breaker
Figure 2 shows wiring for different circuit breakers.
For a single-pole breaker for a 120-volt circuit:
For 2-wire cable plus ground, connect the white wire to the neutral bus bar, and the black wire to the breaker.
For a double-pole breaker for a 240-volt circuit:
If you have a 2-wire cable plus ground, connect both the black and white wires to the breaker, each one to its own screw (it does not matter which goes to which), and tape the white wire black to indicate it is hot.
If you have a 3-wire cable plus ground, connect the black and red wires to the circuit breaker; connect the white wire to the neutral bus bar.
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6.
Install the Circuit Breaker
Press the breaker into place.
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7.
Test the Circuit
Replace the cover, close the panel, and complete the wiring for your project. Then return power to the main breaker and test the circuit.
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