Installing a New Circuit
The receptacles, light fixtures, appliances and switches in your home are all part of multiple electrical circuits, which begin and end in your circuit breaker panel. For example, all the receptacles in a bedroom might be part of one circuit, wired to a single breaker.
For simple additions, such as installing an extra receptacle, you may be able to extend an existing circuit. As long as adding the load doesn’t exceed the circuit breaker’s amperage rating, you can splice wires leading to the new receptacle to the circuit’s existing wire. But if you’re wiring a new room or installing a high-wattage device like a major appliance, you need to add at least one new circuit, with its own circuit breaker in the breaker panel.
Always consult local building wiring authorities before working on your household electrical circuit. New circuit wiring must meet local electrical code standards, and you may need to acquire a permit. Additionally, both your plan and the finished work may need to pass an official inspection, and local authorities may require that a professional electrician handle certain parts of the job.
To install a new circuit, you will need an open slot in your breaker panel for a new circuit breaker. Plan to work during the daytime, as you will need to shut off all power in your home during most of the project.
• Select a circuit breaker designed to handle the load on your new circuit and designed to fit your
• If you aren’t comfortable working with electricity, have a licensed professional install the new
• Install new electrical cable, boxes, devices and a circuit breaker yourself and save.
WHAT YOU NEED FOR THIS JOB:
Step 1: 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 2: 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
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.
a. If you are adding a circuit to a room with unfinished framing, you can mount new-
work boxes directly to wall studs or ceiling joists.
b. If you are adding wiring behind existing drywall, you will need to cut openings in
the wall or ceiling and install remodeling boxes, also known as old work boxes.
Refer to our Installing Remodeling Boxes Project Guide for installation
Step 3: 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.
a. If you are adding a circuit to a room with unfinished framing, drill 5/8 in. holes
through wall studs, and pass the cable through the holes. Typically, cable
should run in a straight line, one foot above your receptacles, but consult your
local electrical code for specific regulations. Secure cable to framing members
using cable staples. Screw protective metal nailing plates to the framing
members at each point where cable passes through. These plates will prevent
someone from accidentally drilling into the electrical cable in the future.
b. If you are adding a circuit in a room with finished walls, you will need to use fish
tape to run cable behind the walls, from electrical box to electrical box. The
simplest approach may be to run cable up into an attic or down into a
basement. Refer to our Installing Electrical Cable Behind Walls Project Guide
for detailed installation instructions.
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
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 4: Run Cable to the Breaker Panel
Inside the breaker panel, you’ll find a grounding bus bar and a neutral bus bar on
Step 5: Wire the New Circuit Breaker
For information on AFCI circuit breakers, see our Installing an AFCI Circuit Breaker Project Guide.
120-Volt and 120/240 Volt Circuits:
Straight 240-Volt Circuits:
Step 6: 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
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.