Light switches are one of the most common items you will install as a commercial electrical subcontractor. They come in various types, but they all serve the same purpose: to turn something on or off. And what they turn on or off can be anything from a light to a fan to an industrial machine.
Whether upgrading an old light switch to a modern touch screen system or replacing a switch, it’s critical to understand what it does and how it works so that you can make an informed decision for your next project. This is to ensure that it’s working properly and that the structure is safe from electrical fires and other hazards.
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What Is a Light Switch?
Switches are used to open and close circuits by performing ON and OFF functions. They can be used for many different purposes, including controlling lights and appliances, opening locked doors or windows, as well as other commercial and industrial applications. Light switches control the flow of electricity to light a group of light fixtures in a room or space. They are usually wall-mounted and have a switch plate that covers the switch.
Elements of a Light Switch
Switch markings are symbols printed on switches to indicate their function, type, size, voltage, and current ratings. Switch markings include letters that indicate the switch’s status, such as “on” or “off,” as well as letters that identify the switch type, such as “D” for double pole and “C” for single pole.
Color coding is a technique used to identify the switch terminal screws and wirings by using various colors. For example, a black wire is used for the live wire, and a white wire is used for the neutral wire.
The UL label is a stamp that indicates that a device meets the safety standards established by Underwriters Laboratories Inc., created by the National Board of Fire Underwriters. Any UL-certified light switch should provide years of trouble-free operation without causing any electrical problems for its users.
The Canadian Standards Association (CSA) label is a marking found on devices that meet the standards set by CSA. Devices that bear CSA and UL labels indicate that they are accepted in Canada and the United States.
The conductor symbol is a marking printed on a switch to indicate the size and type of conductor that can be used with the switch.
Current and Voltage Ratings
The current and voltage ratings indicate the maximum amount of current and voltage the switch can handle.
The T ratings of the switch indicate the maximum temperature that the switch can withstand.
Types of Light Switch Circuits
To make a switch work, there must be a circuit between the power source and the load. The load is the device that the switch controls, such as a light fixture. The power source is the electrons flowing through the circuits.
The type of circuit will determine how the switch is wired. Here are the types of switch circuits:
Single-Pole Switch Circuit
A single-pole switch circuit controls one wire and makes one connection: the ON/OFF switch. When the switch is turned ON (closed), current flows through the two terminals, and when the switch is turned off (open), no current flows between the two terminals.
Double-Pole Switch Circuit
A double-pole switch circuit is one in which two switches control the flow of electricity in a circuit. This type of circuit is often used to control two different things independently, such as a light and a fan.
Three-Way Switch Circuit
A three-way switch circuit is one in which three switches control the circuit. The three switches can turn the circuit on or off from two separate locations.
Four-Way Switch Circuit
In a four-way switch circuit, four terminals control the circuit. The four switches can turn the circuit on or off from three separate locations.
Types of Light Switches
A single-pole switch is a type of light switch with two screw terminals used to control just one light fixture or another device from a single location. It’s called a single-pole switch because it has two wires connected or separated by the switch mechanism. The advantage of this type of circuit is that it is easy to wire up and requires less wiring than other types of circuits.
A three-way switch is a type of switch that features three terminals and can control one fixture from two different locations. This switch doesn’t have on/off indicators on its toggles because it is usually paired with another switch. You can find three-way switches in stairwells or lengthy halls.
Four Way Switch
A four-way switch is similar to a three-way switch, except that it has four terminals, including a ground terminal, and controls one fixture from three different locations. This switch must be paired with two three-way switches to create a circuit. They are found in stairways, hallways, and large rooms.
Double-Pole Single-Throw Switch
A double-pole single-throw switch controls two electric circuits using a single toggle and two states: “on” and “off.” A double pole single throw switch has two inputs and two outputs, totaling four terminals controlled by the same switch.
A duplex switch controls two electric circuits with two toggles. This switch controls two lights or other appliances from two different locations.
This switch combines a light switch and a receptacle (outlet) into one unit. In this switch, the receptacle can be controlled by a switch separate from the receptacle. This switch controls a receptacle that is not easily accessible, such as a recessed outlet.
A dimmer is a switch that allows you to adjust the brightness of a light. The light can be dimmed by turning the switch to a lower setting. It typically has three positions: off, dimmed, and brightened. This switch is available in single-pole or three-way operation.
A key switch is a switch that includes a lock. This increases operational safety because only those with the necessary key can activate the switching operation.
AC Push Button
An AC pushbutton is a switch activated by pressing a button and deactivated by releasing the button. The AC push button controls a circuit that is not easily accessible or in a difficult-to-reach location.
A weatherproof switch is designed for an outdoor setting. This switch is made of weather-resistant materials and is sealed to keep moisture and dust out.
A timer switch is designed to turn an electric circuit on and off at predetermined times. These switches are often used with a light sensor to control outdoor lights.
A motion sensor switch is designed to turn an electric circuit on and off when motion is detected. This type of switch is often used in security applications.
Pilot Light/Switch Combination
A pilot light/switch combination has a built-in pilot light. The switch is used to control an electrical circuit, and the pilot light indicates whether the switch is in the ON or OFF position.
A switch-fuse combination controls an electric circuit with a single toggle. The switch is built into the fuse, which can be controlled by a switch separate from the fuse. The fuses/switch combination switch is used to control a circuit that is not easily accessible, such as those behind a wall.
A low-voltage switch is designed to control a low-voltage circuit. Low-voltage circuits are typically found in lighting and security systems and are often used with low-voltage transformers to convert a high-voltage circuit into a low-voltage one.