- Home
- How To
- Project Guides
- Project Guide: Installing a New Circuit
Installing a New Circuit
|
Follow These Steps
Step One
| Plan the Circuit |
| 1. | Measure the room or rooms where you’ll be installing the circuit, and draw a detailed, accurate floor plan. Make multiple copies, so you can start over with your circuit plan if you make mistakes. |
| 2. | On the floor plan, mark the position of every receptacle, switch, fixture and major appliance you plan to add to the circuit. |
| 3. | Draw lines representing the electrical cable for the circuit. The electrical cable should begin in the breaker panel and run to every device in the circuit. |
| 4. | Add up the wattage for all the devices you expect to connect to the new circuit. This will give you the new circuit’s total load. |
| 5. | Determine what type of circuit breaker you need to install, based on the total circuit load. All circuit breakers have a safe load capacity rating. For example, a 15-amp circuit breaker has a safe load capacity of 1,440 watts and a 20-amp circuit has a safe capacity of 1,920 watts. If you expect the total load will be greater than 1,920 watts, you will need to install two separate circuits. Permanently installed appliances, such as A/C units, washing machines and ovens, require their own dedicated circuit. Refer to our Circuit Breaker Buying Guide for specific guidelines on matching different loads to breaker types. Consult an electrician if you are unsure of your total circuit load. |
| 6. | Verify that your breaker panel can handle a new circuit. Your breaker panel’s amperage rating will be listed on the main breaker. Newer homes will have a 100-amp, 150-amp, or 200-amp rating, while some older homes may have a 60-amp rating. The rating tells you how much total current each of two vertical columns of individual circuit breakers can deliver at one time. |
Step Two
| Install Electrical Boxes |
| 1. | Consult your local electrical code for regulations on how and where you can install new-work or remodeling electrical boxes. The local code may also require specific types of electrical box for certain applications. | ||||
| 2. | Select the electrical box you need for every receptacle, switch and fixture in your new circuit. Our Electrical Box Buying Guide explains the functions of the different box designs. | ||||
| 3. | Shut off the main power on your circuit breaker panel before you begin installation work, in case you come into contact with existing electrical cable behind your walls. | ||||
| 4. |
Install the appropriate electrical boxes for every device in your circuit, as
laid out in your circuit plan.
|
||||
Step Three
| Run Cable to Devices |
| 1. | Be sure to select cable that can handle the load on your new circuit. Consult your local electrical code for specific guidelines. | ||||
| 2. |
Run cable between electrical boxes, as laid out in your circuit plan.
|
||||
| 3. | Run cable from the first electrical box in the circuit to your breaker panel location, as laid out in your circuit diagram. Do not wire the cable to your breaker panel at this time. | ||||
| 4. | At each electrical box, wire the cable to the receptacle, switch, fixture or appliance specified in the circuit plan. Refer to our Electrical Project Guides for specific instructions on installing different devices in a circuit. | ||||
Step Four
|
Run Cable to the Breaker Panel
Inside the breaker panel, you’ll find a grounding bus bar and a neutral bus bar on opposite sides of the panel. Each has multiple setscrew terminals for wires. Two hot bus bars, which provide electrical power to all household circuits, run down the middle of the panel, with breakers on either side of them. |
| 1. | Make sure the main breaker switch is in the off position. Before you begin work on the breaker panel, all the wires and circuit breakers in the panel must be de-energized. If you have a separate main disconnect, switch it off as well. This may be in a panel outside your house, near the electrical meter. |
| 2. | Remove the screws fastening the breaker panel cover, and pull the cover off the breaker panel. |
| 3. | Confirm that power is shut off using a neon tester. Hold one probe against the neutral bus bar while touching the other probe to both setscrews on a double-pole breaker. Note that there are two thick black cables running to the main circuit breaker. Be careful to never touch these cables, which are always energized. |
| 4. | Remove one knockout slug from the side of the breaker panel. First, use a hammer to tap the knockout slug with a screwdriver. Then, use a pair of pliers to twist off the slug. |
| 5. | Insert a cable clamp into the open knockout. |
| 6. | Use a cable ripper to strip about 12 in. of sheathing from the end of the cable. Cut off the excess sheathing with a utility knife. |
| 7. | Feed the cable through the cable clamp until there is a ½ in. of sheathed cable inside the breaker panel. Tighten the cable clamp to secure the cable. |
Step Five
Wire the New Circuit Breaker
For information on AFCI circuit
breakers, see our Installing
an AFCI Circuit Breaker Project Guide.
| 1. | Insert the end of the bare, copper-colored grounding wire into an open terminal in the grounding bus bar and tighten the setscrew to secure the wire. If it is the main service panel and there is no separate grounding bus bar, connect the grounding wire to the neutral bus bar instead. Position the excess grounding wire so it runs along the inside edge of the panel, away from the bus bars. |
120-Volt and 120/240 Volt Circuits:
| 2. | Use a wire stripper to remove a ½ in. of insulation from the white neutral wire. |
| 3. | Insert the end of the neutral wire into an open terminal on the neutral bus bar and tighten the screw. |
| 4. | Strip away a ½ in. of insulation from the black hot wire. If you’re adding a 120/240 volt circuit, strip away a ½ in. of insulation from the red hot wire as well. |
| 5. | Insert the end of the hot wire into the terminal on the new circuit breaker, and tighten the setscrew. In a 120/240 volt circuit, connect the red hot wire to the second circuit breaker terminal. |
| 6. | Lock the new circuit breaker into an open slot, by slipping the side with the attached hot wire under the tab beside the hot bus bar. Push the other side in, toward the bus bar, until it snaps into place, flush with the other breakers in the panel. |
| 7. | Position the excess neutral and hot wire around the inside edge of the panel, away from the bus bars. |
Straight 240-Volt Circuits:
| 2. | Use a wire stripper to remove a ½ in. of insulation from the ends of both hot wires. |
| 3. | Insert the end of each hot wire, which will typically be black and red, into a terminal on the new circuit breaker, and tighten the setscrews. There is no neutral wire in this type of circuit. |
| 4. | Position the excess hot wires around the inside edge of the panel, away from the bus bars. |
Step Six
| Replace the Panel Cover and Test |
| 1. | Use a pair of pliers to remove the breaker knockout on the panel cover that corresponds to the position of the new circuit breaker. With a double-pole circuit breaker, you will need to remove two knockouts. |
| 2. | Replace the panel cover and tighten the screws to reattach it to the panel housing. |
| 3. | To avoid a power surge, switch off all the individual circuit breakers before switching on the main breaker. |
| 4. | Switch on the main breaker and then switch on the individual circuit breakers, one by one. |
| 5. | Label the new circuit breaker on the breaker panel cover. |
| 6. | Test each of the receptacles, switches, fixtures or appliances on the circuit to ensure the installation was successful. |
Your Projects
Log In to Access Your Projects