2011 NEC Fan Light Switched Together 3 way switches, power at switch, 3 wire (plus ground cable being routed thru the ceiling box onward to other switch

Connections Instructions:

(as depicted in the diagrams above)

At the Fixture box…

Two cables entering this box; one cable from switch 1, one cable from switch 2.

• a) using an insulated wire nut connect / join the white wire from switch 1 + the white wire from switch 2 + the connection to the grounded conductor (neutral) of the fan / light combo fixture.
• b) using an insulated wire nut connect / join the black wire coming from switch 1 + the blue wire from switch 2.
• c) using an insulated wire nut connect / join black wire from switch 2 + the switched ungrounded conductor (hot) from light (shown as black in diagram) + the switched ungrounded conductor (hot) from fan (shown as red in diagram)
• d) using an insulated wire nut connect / join the red wire from switch 1 + the red wire from switch 2.
  *e) please see under important notes in regards to the equipment grounding conductor (bare wire).

At switch 1 box…

Two cables entering this box, one coming from fixture, and one is the ‘circuit power supply cable’

• a) connect the black wire coming from ‘circuit power supply’ cable to the common screw of switch 1.
• b) connect the white wire coming from fixture to the white wire from the ‘circuit power supply’ cable.
• c) connect the black wire coming from fixture to the on the remaining main screws of switch 1.
• d) connect the red wire coming from fixture to the last remaining main screws of switch 1.
  *e) please see under important notes in regards to the equipment grounding conductor (bare wire).

At switch 2 box…

One cables entering this box coming from fixture.

• a) connect the black wire coming from fixture to the common screw of switch 2.
• b) connect the blue wire coming from fixture to one of the remaining main screws of switch 2
• c) connect the red wire coming from fixture to the last remaining main screws of switch 2.
• d) using an insulated wire nut cap off the white wire.
• e) please see under important notes in regards to the equipment grounding conductor (bare wire).

Important Notes:

By electrical codes you MUST have at least 6 inches of wire in the electrical box itself, and also the wire must be able to reach at least 3 inches outside the box, it can fail an electrical inspection if the required min. wire length is not met. You may have the wires a bit longer (within reason) but they cannot be shorter. Also see the note on box fill further down in this article.

Use wire nuts of the correct size to join wires together. For fan / light combination fixtures, most likely it will have wire connections, the white wire will be the grounded conductor (neutral) , any green wires are equipment grounding conductors, then there will be two other wires one will be the switched ungrounded conductor (hot) for the light, and one will be the switched ungrounded conductor (hot) for the fan.. If you are confused please post to our forums for further clarification.

What is not shown in the drawings to avoid confusion, is that each wire cable also has a bare equipment grounding wire included. This wire is connected to a grounding screw in each electrical box (if the box is metal), joined either through the grounding screws in the box itself or via a wire nut to the bare wire of the next cable entering / exiting the box, it is also connected to any grounding screw (if there is one) on the switch itself, as well as any grounding screw at the fixture (green wires that attach to the fixture are grounds). Now if using a plastic box, it is made of a material that is non conductive, however some plastic boxes have a metal strip inside that can still be used to connect equipment grounding wires, in the event that it does not use wire nuts to join the bare grounding wires together. The equipment grounding wire (bare in most cables) must be electrical conductively joined throughout the circuit. Green wires are also equipment grounding conductors.

At the switch itself there are 3 main electrical screws, one of these 3 screws is distinctly different in color (perhaps darker) than the other 2. This screw connection is called the common screw. It is very important that in order for the 2 switches to work as they are intended to that the correct wire is attached to the common screw. Basically as depicted in the drawings one switch has the ungrounded conductor (hot) from the circuit power supply cable attached to the common screw, where the other switch had the ungrounded conductor (hot) feed to the light fixture itself.

Please also note that there are a variety of manufactures out there that make 3 way switches so it is possible that the switch you buy may have the common screw located in a different spot or side of the switch then depicted in the drawings in this article, just make sure that the wire depicted to go to the common screw of each of the switches is actually connected to the common screw of the 3 way switch you bought. The other 2 wires going between the remaining screws of one switch to the other switch does not matter as long as one wire of the 2 remaining wires go on each of the remaining 2 screws of the screw.

If there is an equipment grounding screw on the 3 way switch it may be green in color and be separated away from the main connections of the switch and likely part of the metal frame that is also part of the mounting structure of the switch.

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Extensions to this Switch circuit…

Be Aware that there is a limit by code on how many wires can be in a given size electrical box, when adding more wires to the same box you may have to install a larger and / or deeper box to allow space for more wires coming and out of the box.

Here is an article / explanation in regards to box fill calculations ‘Box Fill Calculation’

The instructions here are based on the fact that the circuit has already been wired to the configuration shown in this article and we are now making the wiring changes for onward power.

From the switch locations….

Switch 1 onward options…

(only onward always on power is available)

‘Always on’ power…

(showing bellow the switch 1 portion of the circuit)

Not shown in the diagram but the onward cable also has a bare wire (equipment grounding conductor) that also must be connected to all the other bare wires at the switch electrical box.

Connection Instructions for onward cable (always on)

(only the changes to the wiring are described here)

• a) Using an insulated wire nut, attach / join – the white wire of onward cable + the white wire coming from fixture + the white wire coming from ‘circuit power supply’ cable
• b) Using an insulated wire nut, attach / join – the black wire of onward cable + the black wire coming from ‘circuit power supply’ cable + the black wire connected to the common screw of switch 1.

Identification of wires in onward cable….

Black – Ungrounded conductor (hot – always on)
White – Grounded conductor (neutral)

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Switch 2 onward options…

(only onward switched power is available)

Switched power…

(showing bellow the switch 2 portion of the circuit)

Not shown in the diagram but the onward cable also has a bare wire (equipment grounding conductor) that also must be connected to all the other bare wires at the switch electrical box.

Connection Instructions for onward cable (switched)
(only the changes to the wiring are described here)

• a) Using an insulated wire nut, attach / join – the white wire of onward cable + the white wire coming from fixture.
• b) Using an insulated wire nut, attach / join – the black wire of onward cable + the black wire coming from fixture + the black wire connected to the common screw of switch 2.

Identification of wires in onward cable….

Black – Switched ungrounded conductor (hot – switched)
White – Grounded conductor (neutral)

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At Fixture onward options…

(only switched power is available)

‘Switched’ power…

Because there are so many wires at the fixture location, I have decided not to make a diagram but to just describe the changes required.

Not in the description but the onward cable also has a bare wire (equipment grounding conductor) that also must be connected to all the other bare wires at the fixture electrical box.

Connection Instructions for onward cable (switched)
(only the changes to the wiring are described here)

• a) Using an insulated wire nut, attach / join – the white wire of onward cable + the white wire connected to the grounded conductor (neutral) of fan / light combo fixture + the white wire coming from switch 1 + the white wire coming from switch 2.
• b) Using an insulated wire nut, attach / join – the black wire of onward cable + the black wire coming from switch 2 + the switched ungrounded conductor (hot) from light (shown as black in diagram) + the switched ungrounded conductor (hot) from fan (shown as red in diagram)

Identification of wires in onward cable….

Black – Switched ungrounded conductor (hot – switched)
White – Grounded conductor (neutral)

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Foreign Users:

The colors of the wires depicted are based on the standards and code requirements / configuration in the United States and Canada. If you are viewing this site from a foreign country, your wiring standards and color of wires may be different but the principal and sequence of wiring will still remain the same. Therefore the information in this article may still be of use to you regardless of what country you may be in. Just translate the colors used here to the color of wires used in your country in regards to ungrounded (hot) conductors / grounded conductors (neutral) and equipment grounding conductors as well know applicable code requirements in your country.

WHILE EXTREME CARE HAS BEEN IMPLEMENTED IN THE PREPARATION OF THIS SELF-HELP DOCUMENT, THE AUTHOR AND/OR PROVIDERS OF THIS DOCUMENT ASSUMES NO RESPONSIBILITY FOR ERRORS OR OMISSIONS, NOR IS ANY LIABILITY ASSUMED FROM THE USE OF THE INFORMATION, CONTAINED IN THIS DOCUMENT, BY THE AUTHOR and / OR PROVIDER.

By: Donald Kerr