Electrical Switches

When describing an electrical switch, the number of poles indicates how many circuits a switch can control. Single-pole switches control one electrical circuit; double-pole switches control two. Throw, in contrast, indicates how many outputs a pole can connect to. Electrical switches can be grouped into four categories by functionality:

• Single pole, single throw (SPST) switch: This is the most basic type of switch and the kind most often found in residential homes. An SPST is an on/off switch with a single circuit and two electrical connection points. Flipping the switch on establishes the flow of electrical current between the two terminals.
• Single pole, double throw (SPDT) switch: This switch has three terminals – one for input and two for output. Only one completed circuit can exist at a time, so if one output such as an outlet or receptacle is engaged, the other is turned off.
• Double pole, single throw (DPST) switch: A DPST switch uses a single toggle or button to turn two circuits on or off. The DPST switch has four terminals: two inputs and two outputs.
• Double pole, double throw (DPDT) switch: A DPDT has six terminals – two inputs and four outputs. Each of the poles can complete two different circuits.

While there are many different kinds of switches, these three styles are the most common in residential homes:

• Toggle: This is the most common style and is what most people picture when they imagine a light switch. A toggle switch has a single small lever that sticks out from a metal or plastic faceplate. Flipping the toggle up connects the circuit, providing electricity to a light fixture or appliance. Flipping the toggle down disconnects the power to the output.
• Rocker: A rocker switch works the same way as a toggle switch; it simply has a different appearance. This kind of wall switch is wider and flatter, so it’s more flush against the wall plate.
• Dimmer: These switches allow you to adjust the brightness of a light fixture via a dial or slider. Instead of simply switching a light on or off, rotary switches or slide dimmer switches set different levels of ambient light.

Note that while you can use almost any type of dimmer switch for traditional incandescent bulbs, light-emitting diode (LED) and compact fluorescent (CFL) fixtures require dimmer switches that are specifically designed for these bulbs.

Here are the five main types of electrical switches used in homes:

• Single pole: This is usually a typical toggle or rocker switch with on and off markings. A single-pole switch has two screw terminals attached to the body of the switch where the black electrical wires are connected and do not have a neutral wire. Single-pole switches are primarily used for light fixtures, but they can also be used to control appliances such as garbage disposals. A pull chain for an overhead light or ceiling fan is another common type of single-pole switch.
• Double-pole: This switch has an on/off toggle like a single-pole switch, but it controls two circuits. Double-pole switches are more common in industrial buildings, but they are sometimes used in homes that have 240-volt appliances, such as a hot tub or an electric water heater.
• Three-way: These switches are used in sets of two. You’ve probably seen three-way switches used on a staircase, with one switch at the top and another at the bottom.
• Four-way: A four-way switch is only needed if you want to control a light from three or more locations. This can be helpful in a great room or a long hallway.
• Smart switch: As IoT technology becomes more widely available, some homeowners are installing smart lighting systems with timers, adjustable settings, and preset programs. These can be controlled from an app on your phone or tablet, or even through a voice assistant like Google Home or Alexa.

If you've ever had to reset a circuit breaker in your home, you’ve probably seen the two columns of switches in your breaker box. A circuit breaker panel usually has single-pole and double-pole switches.

Single-pole circuit breakers supply 120-volt power to a circuit and protect one electrified wire. In contrast, double-pole breakers protect two wires. They may supply 120V or 240V. In case of overloads or short circuits, both types of breakers will trip.

Double-pole breakers are more common in commercial and industrial buildings than they are in homes. And new homes will usually have some special circuit breakers with extra protections, like ground fault circuit interrupters (GFCI), arc fault circuit interrupters (AFCI), or combination arc fault circuit interrupters (CAFCI).

A single-pole switch operates one circuit. It has two brass-colored screw terminals that attach to the body of the switch, plus a green screw that connects to a metal strap. Each brass screw terminal connects to an electrified wire. A bare copper wire grounds the circuit and is attached to the green screw. Single-pole switches are rated for 15-amp or 20-amp power.

A double-pole switch controls two circuits instead of one. The switch will have four screw terminals that control two separate hot wires, as well as the green grounding screw. Most double-pole switches are rated for 30 or 40 amps and handle 240-volt circuits, so they can control higher-demand applications.

With an extensive selection of electrical supply products from trusted brands, HomElectrical is your one-stop shop for renovations, construction jobs, and DIY projects. In addition to electrical switches, connectors, and wiring devices, we also carry LED lighting, HVAC system equipment, appliances, and tools.

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