How To Wire A Fan/Light Switch

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You can install the wiring a combination ceiling light/fan unit by following these diagrams and step by step instructions.

Installing a ceiling fan/light combination is a common home improvement project. The part of these projects that confuse many new do-it-yourself persons is how to wire the electrical wiring, so the fan and the light can be controlled by separate, wall-mounted switches. Many handy persons who are ready to tackle any carpentry, painting or plumbing project without any hesitation shy away from tackling electrical projects. There is no reason to pay a professional electrician $50 to $100 an hour when you can do it yourself. After reading this how-to guide, you will know how the fan/light circuit works and will be able to wire your fan/light switches with confidence.

How is the home Cable Run?

In the electrical trades, “home-run” refers to the cable bringing the power from the service panel. Depending on whether the service panel is closer to the ceiling outlet box or the device box that will house the switches, the home-run cable will either enter the ceiling outlet box or the wall-mounted device box. The way you wire the switches will depend on whether the power is brought to the ceiling outlet box or to the device box that will house the switches.

What type of single-pole switch to install

You will install 15-Ampere, 120-volt, single-pole toggle switches, but their physical configuration will depend on whether they are being installed in a single-gang or a double-gang device box. If they are to be installed in a single-gang device box, the device box normally occupied by a single switch, you will need to use a double switch. A double-switch has two switches mounted on a one mounting strap. If you are installing them in a double-gang box, a box designed to hold two switches or two receptacles, you will install two separately mounted switches. For this tutorial's illustrations, I'm using a double-gang device box and two separately mounted switches.

How to wire the switches: With the home-run terminating in the device box holding the switches.

Diagram 1

When the power is brought to the switches, a 12/3 w/Gr Romex cable is run from the switches to the ceiling outlet box. The 12/3 w/Gr cable contains three insulated conductors—one red, one black and one white—and one bare copper conductor.

The home-run cable from the circuit breaker panel is brought to the switches when the switch location is closer to the circuit breaker panel than the ceiling outlet box. As a rule, you will run a 12/2 w/Gr Romex cable from the breaker panel to the two-gang device box as the home-run cable. You could run a 14/2 w/Gr Romex cable and protect it with a 15-Ampere breaker, but few professional electricians install anything less than 20-Ampere branch circuits today. It is sound practice to install 12/2 and protect it with a 20-Ampere breaker because you may want to add other loads to the circuit at some time in the future. The home-run cable contains three conductors—one black insulated conductor, one white insulated conductor and one bare copper conductor.

As you see in this diagram, the black wire bringing power to the switches is connected to the bottom brass color screws on the switches by black pigtail wires that are connected to the black circuit wire in a three-way splice.

How to make a pigtail splice

  1. Making a pigtail splice is a straight forward process. Here, is how to do it like a professional electrician.
  2. Cut each pigtail wire 6 to 8 inches long. Looking at diagram 1, you will see that you will need two black pigtails and two bare copper pigtail wires.
  3. Remove ¾ of an inch from each end of the insulated pigtail wires.
  4. Make an open loop on one end of the pigtail wires, the loop will be used to connect the pigtail wires to the switches.
  5. Hold the other end of the pigtail wires next to the stripped end of the circuit conductor of the same color and twist tightly together with Electrician's (Lineman's) pliers. Twist them together in a clockwise twist. Remember that every solid electrical connection starts with a solid mechanical connection. Complete the splice by screwing a wire nut on the spliced end.
  6. Double-check to be sure that no bare copper is showing from beneath the wire nut when splicing an insulated wire. If bare copper wire shows outside the wire nut, remove the wire nut and cut the stripped splice as needed, then replace the wire nut.

Connecting the white, neutral wire

As you will see from diagram 1, the neutral wire from the breaker panel is spliced together with the neutral wire from the light. Splice the two neutral wires together in the same manner as you spliced the pigtail wires to the circuit wires.

Connecting the switches

  1. Connect the black pigtail wires to the bottom, brass colored screws on the switches. The loops should be placed around the screws in a clockwise direction so that the wire will be pulled tighter under the screws as the screws are tightened down on the wire. Never placed the loops in a counterclockwise direction because the wire will be forced out from under the screws as the screws are tightened.
  2. Connect the red wire traveling on to the ceiling outlet box to the brass screw on one switch and the black wire going to the ceiling outlet box to the top brass screw on the other switch.
  3. Attach the bare copper ground pigtails to the green, octagon-shaped screws on the switches.
  4. Connecting the fan/light unit.
  5. Connecting the fixture is a straightforward process of splicing the circuit wires to the fan/light unit's fixture wires. Splice black to black, white to white, red to red and bare ground to bare ground.

How to wire the switches: With the home-run terminating in the ceiling outlet box

Diagram 2

Wiring the switch-leg

When the home-run cable enters the ceiling outlet box, the 12/3 w/Gr Romex cable running to the switches is referred to as a switch-leg. Normally, the National Electrical Code (NEC) only permits a white, insulated wire to be used as a circuit neutral. There are a few exceptions to that rule. One of those exceptions permits a white, neutral wire to be used a hot wire when it is properly re-identified by painting it or wrapping it with a color tape. In this case, you will see that it has been re-identified by wrapping it with black, plastic electrical tape. We could have used any color tape except white or green tape because white is for a neutral conductor, and green is for a grounding conductor. In a switch-leg, the re-identified neutral is used to carry the power from the black, home-run wire to the switches.

Wiring the switches

Connect the re-identified white, neutral wire to the two, bottom brass screws on the two switches using black pigtail wires. Connect the red and black switch leg wires to the top brass screws on the switches and the bare ground wire pigtails to the two green, octagon-shaped screws.

Wiring the light/fan unit

Connect the home-run neutral wire to the white fixture wire. Connect the home-run bare, copper ground wire in a three-way splice with the fixture ground wire and the switch-leg ground wire. Connect the red and black switch-leg wires to the red and black fixture wires.


Posted on Nov 29, 2012
Ken Brace
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Ron Siojo
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