In Canada, the wiring of 3-way switches is governed by the Canadian Electrical Code (CEC). A 3-way switch setup allows you to control a single light fixture from two different locations. The key components are two 3-way switches and a set of "traveler" wires that connect them. Each 3-way switch has a "common" terminal and two "traveler" terminals. Here are the three common methods to wire 3-way switches, keeping in mind the CEC requirements, particularly the need for a neutral conductor at each switch box (Rule 14-602 (1)). This rule has made older "switch loop" configurations (where only two wires were run to the switch, and the neutral was only at the fixture) generally non-compliant without modification. **Important Note:** Always consult the latest edition of the Canadian Electrical Code (CEC) and, if unsure, hire a licensed electrician. Electrical work can be dangerous and should only be performed by qualified individuals. ### Common Wiring Methods for 3-Way Switches (CEC Compliant): 1. **Power at the First Switch Box (and Neutral at Both Switch Boxes)** This is one of the most common and straightforward methods, often considered the preferred way due to the neutral requirement. * **Description:** The incoming power (hot and neutral) goes into the first 3-way switch box. A 3-conductor cable (plus ground) runs between the two 3-way switches, carrying the two "traveler" wires and a neutral. A 2-conductor cable (plus ground) runs from the second 3-way switch to the light fixture. * **Wiring Breakdown:** * **At the First Switch Box:** * The incoming **hot (black)** wire connects to the **common** terminal of the first 3-way switch. * The incoming **neutral (white)** wire is pigtailed and connected to the neutral wire of the 3-conductor cable going to the second switch. * The two **traveler wires (red and black, or identified as travelers)** from the 3-conductor cable connect to the **traveler terminals** of the first 3-way switch. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). * **At the Second Switch Box:** * The two **traveler wires** from the 3-conductor cable connect to the **traveler terminals** of the second 3-way switch. * The **neutral (white)** wire from the 3-conductor cable connects to the neutral wire of the 2-conductor cable going to the light fixture (and pigtailed to the switch box if necessary for future devices, even if not directly used by the 3-way switch itself). * The **common** terminal of the second 3-way switch connects to the **switched hot (black)** wire of the 2-conductor cable going to the light fixture. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). * **At the Light Fixture:** * The **switched hot (black)** wire from the second switch connects to the **hot** terminal of the light fixture. * The **neutral (white)** wire from the second switch connects to the **neutral** terminal of the light fixture. * The **ground wire** connects to the fixture's ground terminal and the box (if metal). 2. **Power at the Light Fixture Box (and Neutral at Both Switch Boxes)** This method is also common, especially when the power source is closer to the light fixture. * **Description:** The incoming power (hot and neutral) goes into the light fixture box. A 3-conductor cable (plus ground) runs from the light fixture box to the first 3-way switch. Another 3-conductor cable (plus ground) runs between the two 3-way switches. * **Wiring Breakdown:** * **At the Light Fixture Box:** * The incoming **hot (black)** wire connects to one of the **traveler wires** (e.g., black) of the 3-conductor cable going to the first switch. This wire effectively becomes a *continuous hot* to the first switch. * The incoming **neutral (white)** wire is pigtailed to the light fixture's neutral terminal and to the neutral wire of the 3-conductor cable going to the first switch. * The **switched hot (black)** wire coming back from the second switch (via the 3-conductor cable between switches and then the 3-conductor cable to the light) connects to the **hot** terminal of the light fixture. * All **ground wires** are connected together and to the fixture and the box (if metal). * **At the First Switch Box:** * The **continuous hot (black)** wire from the light fixture box connects to the **common** terminal of the first 3-way switch. * The **neutral (white)** wire from the light fixture box is pigtailed to the neutral wire of the 3-conductor cable going to the second switch. This fulfills the neutral requirement at the switch box. * The two **traveler wires (red and black, or identified as travelers)** from the 3-conductor cable going to the second switch connect to the **traveler terminals** of the first 3-way switch. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). * **At the Second Switch Box:** * The two **traveler wires** from the 3-conductor cable coming from the first switch connect to the **traveler terminals** of the second 3-way switch. * The **neutral (white)** wire from the 3-conductor cable is pigtailed and available in the box. * The **common** terminal of the second 3-way switch connects to one of the **traveler wires** (e.g., red) of the 3-conductor cable going back to the light fixture box. This red wire will carry the switched hot back to the light. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). 3. **Power at the Mid-Point Switch Box (and Neutral at All Switch Boxes)** This scenario occurs when the power source happens to enter the system at one of the 3-way switch locations, and the light fixture is located elsewhere. * **Description:** The incoming power (hot and neutral) enters one of the 3-way switch boxes, which acts as the "mid-point" for the power distribution to the light and the other switch. A 3-conductor cable (plus ground) runs to the other 3-way switch, and a 2-conductor cable (plus ground) runs to the light fixture from the mid-point switch. * **Wiring Breakdown:** * **At the Mid-Point Switch Box (where power enters):** * The incoming **hot (black)** wire connects to the **common** terminal of the 3-way switch. * The incoming **neutral (white)** wire is pigtailed and connects to the neutral wire of the 3-conductor cable going to the other 3-way switch, AND to the neutral wire of the 2-conductor cable going to the light fixture. * The two **traveler wires (red and black, or identified as travelers)** from the 3-conductor cable going to the other switch connect to the **traveler terminals** of the 3-way switch. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). * **At the Other Switch Box:** * The two **traveler wires** from the 3-conductor cable connect to the **traveler terminals** of this 3-way switch. * The **neutral (white)** wire from the 3-conductor cable is pigtailed and available in the box, fulfilling the neutral requirement. * The **common** terminal of this 3-way switch connects to one of the **traveler wires** (e.g., red or black, depending on your convention) of the 3-conductor cable going back to the mid-point switch. This wire will carry the switched hot back. * All **ground wires** are connected together and to the switch's ground screw and the box (if metal). * **At the Light Fixture:** * The **switched hot (black)** wire from the mid-point switch connects to the **hot** terminal of the light fixture. * The **neutral (white)** wire from the mid-point switch connects to the **neutral** terminal of the light fixture. * The **ground wire** connects to the fixture's ground terminal and the box (if metal). **Key CEC Considerations for 3-Way Switches:** * **Neutral Conductor Requirement:** As mentioned, Rule 14-602 (1) of the CEC requires that all boxes intended for future installation of control devices (like smart switches, dimmers, etc.) must have a neutral conductor present. This typically means running a 3-conductor cable (plus ground) between 3-way switches and ensuring a neutral is available in each switch box. * **Wire Color Coding:** While the CEC dictates the purpose of certain wire colors (e.g., green or bare copper for ground, white for neutral), the use of black and red for travelers is common, but it's crucial that any white wire used as a "hot" or "traveler" (which is sometimes done in specific scenarios, especially in older installations or with multi-conductor cables) must be re-identified at both ends (e.g., by taping it with black or red tape) to indicate its hot purpose. However, with the neutral requirement, using a 3-conductor cable for travelers that includes a dedicated neutral simplifies compliance. * **Common Terminal:** On a 3-way switch, the common terminal is usually marked with a different color screw (often black or darker than the traveler terminals) or labeled "Common." This is where the continuous hot (power in) or the switched hot (power out to the light) connects. * **Traveler Terminals:** The two traveler terminals are typically brass-colored screws. These are for the two wires that go between the 3-way switches. Always ensure all connections are secure, insulation is intact, and proper grounding is maintained for safety. If in doubt, always consult a licensed electrician.