Switches


Figure: Device and Connector Marking Codes for Conductor Types
Device or Connector Type Marking Conductors (Wiring) Allowed
15- and 20-amp receptacles and switches NONE copper, copper-clas aluminum
12- or 20-amp receptacles and switches CO/ALR aluminum, copper, copper-clad aluminum
30-amp and greater receptacles and switches NONE copper only
30-amp and greater receptacles and switches AL/CU aluminum, copper, copper-clad aluminum
Screwless push-in connectors NONE copper or copper-clad aluminum
Wire connectors 1 NONE copper only
Wire connectors 2 AL aluminum only
Any device COPPER ONLY or CU ONLY copper only
Any device CU and CU-CLAD ONLY copper, copper-clad aluminum

Switches should always be wired on a circuit’s hot side — that is, they are only connected to the black wire and rarely connected to the white wire. When necessary, it is permissible to use the white conductor as a hot wire. However, the white wire must be re-identified with black paint at both ends in the switch and fixture boxes so that it does not become confused with the other white wires that are neutral conductors. Some inspectors do not consider tape permanent enough to use as a marker.

Newer switches also have a grounding terminal. When replacing an older switch with a new one, the replacement should match the amperage and voltage ratings of the old switch. It should also be rated for the particular circuit’s wire gauge. Ratings are stamped on the switch (Reading a Switch, below). Common types of residential switches are shown in Common Types of Residential Switches, below.


Figure: Reading a Switch
Switches are rated for a particular wire type and maximum amperage. When using aluminum wiring, use only switches marked CO/ALR, which are safe with either copper or solid aluminum wiring.
Switches are rated for a particular wire type and maximum amperage. When using aluminum wiring, use only switches marked CO/ALR, which are safe with either copper or solid aluminum wiring.

Figure: Common Types of Residential Switches

Single-pole switches have a single set of contacts that are either open or closed, depending upon the position of the switch. This switch controls a fixture or receptacle from only one location (below).

Figure: Single-Pole Switches


Figure: New Dead-End Single-Pole Switches
When a switch is placed after a fixture in a single-pole scenario, the updated code calls for a dedicated neutral conductor in the switch box. A three-conductor cable between the fixture and the switch makes this possible, with the neutral conductor capped off in the switch box for future use.
When a switch is placed after a fixture in a single-pole scenario, the updated code calls for a dedicated neutral conductor in the switch box. A three-conductor cable between the fixture and the switch makes this possible, with the neutral conductor capped off in the switch box for future use.

Three-way switches flip a conducting lever back and forth between two connection points called travelers. These control a lighting load from two locations (below).

Figure: Three-Way Switches After the Fixture
In this three-way switch layout, both switches come after the fixture. To make a dedicated neutral conductor available in each switch box, a three-conductor cable runs from the fixture to the first switch, and a four-conductor cable runs between switches.
In this three-way switch layout, both switches come after the fixture. To make a dedicated neutral conductor available in each switch box, a three-conductor cable runs from the fixture to the first switch, and a four-conductor cable runs between switches.
Three-Way Switches With the Fixture in Between
In the three-way switch scenario shown above, the fixture is placed between the switches. As before, a three-conductor cable joins the first switch and the fixture, but now a four-conductor cable runs from the fixture to the second switch. The capped off neutral is available in the second switch box should it be needed in the future for a device that demands more complex wiring.
In the three-way switch scenario shown above, the fixture is placed between the switches. As before, a three-conductor cable joins the first switch and the fixture, but now a four-conductor cable runs from the fixture to the second switch. The capped off neutral is available in the second switch box should it be needed in the future for a device that demands more complex wiring.


Four-way switches. If a group of lights needs to be controlled from more than two locations, any number of four-way switches may be wired into the circuit in between the two three-way switches. In these switches, there are two hinged conducting levers that swap the power back and forth from two load screws. In a four-way switch, the traveler wires from one three-way are connected on one end, and the traveler wires to the next four-way (or the end three-way) are connected on the other (below).


Figure: Four-Way Switch Loop
Any number of four-way switches may be wired in between a pair of three-way switches to control a light source from more than two points.
Any number of four-way switches may be wired in between a pair of three-way switches to control a light source from more than two points.

Combination switches can include any combination of switches, outlets, and indicator lights. Some combination switches require a jumper between the various parts. If so, the gauge of the jumper should match that of the circuit wire.

Dimmer switches are designed for lights, not for appliances such as ceiling fans, which need special variable-speed switches. Fluorescents require special dimmer switches that will not work unless the light fixture is equipped with a dimming ballast.

A dimmer’s wattage rating should meet or exceed the combined wattage of the lights the dimmer controls, or it will overheat, creating a fire hazard. Standard, low-cost dimmers can handle only 600 watts, restricting them to no more than four 150-watt bulbs. This becomes problematic with track lighting units where any number of lights might eventually be installed. Many electricians use dimmers rated for 1,000 watts or more when installing track lighting. These include an external heat sink to dissipate excess heat.

  1. Nuts, splices, or any device that couples wires together. Marking information is usually on the connector packaging.

  2. Nuts, splices, or any device that couples wires together. Marking information is usually on the connector packaging.

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