Definitions of Electrical Terms The following is not, nor is it intended to be, a complete list of electrical terms. It is, rather, a sampling of definitions, in layman's terms, frequently used by Master Electricians and their clients. Ampere (or Amp) The rate at which electrical power flows to a device. If you think of water flowing through a pipe instead of electricity flowing though wires, it makes sense that a large pipe can carry more water. This is the same with electricity. Larger wires can carry more current which is measured in amperes. Thus, the current-carrying capacity of wires is called amperage, measured in amperes. Most people refer to amperes as 'amps' for short. Breaker A safety device that interrupts an electrical circuit in the event of an overload or short circuit. A circuit breaker is like a fancy switch found at your electrical panel. You can use the breaker to turn on or off an entire circuit - the same as you would use a switch to turn on or off a light. But, in addition to this function, the breaker will automatically 'kick' if too much current is trying to go through it. This limits the amps flowing through the wires on the circuit so that they don't overheat or cause a fire. Circuit breakers have replaced fuses as safety devices since they can be used over and over, instead of once like a fuse. Circuit A continuous loop of electrical current flowing along wires or cables. A particular circuit may be dedicated and supply an individual device, such as your water heater or AC. On the other hand, it may supply a number of devices, such as receptacles, lights, and smoke detectors. The easiest way to determine what devices are 'on' a particular circuit (if you don't have the electrical plan) is to turn off the breaker or pull the fuse and then see what doesn't have electricity anymore. Circuit Breakers See Breaker Control A device or group of devices that serves to govern, in some predetermined manner, the electric power delivered to the device to which it is connected. Thus, a simple switch is a control. So is a dimmer and a thermostat. In the modern-era of technology, a control can come in all shapes and sizes. It may be a computer, or a timer, or a photocell. In fact, many controls nowadays have some type of timer or microprocessor built in so that they can 'remember' scenes. Device A unit of an electrical system that is intended to carry, but not utilize electric energy. Dryer plugs, lamp holders, receptacles, breakers, fuse holders, and switches are all examples of devices. Dimmer Switch A device that incrementally controls the electricity flowing to a load. A dimmer switch, normally used for controlling lights, makes it possible to vary the brightness of a light fixture; or, conversely, to 'dim' it. Dimmers can be toggle-type, dial-type, slide-action, or automatic. Additionally, they can either step-up the level of electricity or they can be continuous. Step-up dimmers allow the brightness of the light to seem to jump to the next level; whereas, continuous dimmers allow you to smoothly increase the brightness of the light. Electrical Plan A diagram which outlines the devices connected to each circuit of each electrical panel. Often called a 'blueprint', the electrical plan is usually prepared by either an Electrical Engineer or a Master Electrician so that all of the electricians on the job know how to connect each circuit. This plan is also a handy reference when future electrical work is done many years after the original installation. Fuse A safety device, usually found in older homes, that interrupts an electrical circuit in the event of an overload or short circuit. By design, fuses can only do their job once and then must be replaced. Fuses have been replaced with circuit breakers in almost all new applications. More often than not, a fuse box, which contains the fuses, should be upgraded to a modern electrical service. GFI (or Ground Fault Circuit-Interrupter or GFCI) A device intended for the protection of personnel that functions to interrupt the flow of electricity in adverse conditions. Commonly found in the form of GFI receptacles, these devices 'kick' at the receptacle to protect people from injury. GFI receptacles should be installed at all damp or wet locations, such as kitchen counters, bathrooms, and outdoors. They are easily recognized by the 'reset' and 'test' buttons on them. Junction Box A container used to house electrical connections. Load A unit of an electrical system that is intended to utilize electric energy. When discussing amperage or wattage, a load is any unit that uses current or power, respectively. Lights, ovens, water heaters, and smoke detectors are common loads. Meter A device used to measure the amount of electrical power being used. Electricians use handheld meters to test individual circuits and the power company uses meters to determine the amount of power usage at each location. The power company's meter is usually glass and can be found outdoors where the electrical power enters the building. Meter Base A metal box that contains the power company's meter. Each meter breaks the service wires so that the power consumed can be measured by the meter. Some meter bases also have local disconnect switches so that a worker can turn off the electrical power at that point. Outlet See Receptacle Overload A demand for more current than the circuit wires or electrical device was designed to carry. An overload will cause a fuse to blow or circuit breaker to trip if they are on the circuit; otherwise, the wire will likely overheat and may cause serious damage. Panel Also known as the service panel or load center, the panel is a metal box usually near the site where the electrical power enters the building. In the panel, electrical current is broken into individual circuits, each protected by a breaker. Most panels have a 'main' breaker that allows you to turn off all of the circuits at the same time. Preset Scene Dimmer A type of lighting automation system that allows a number of scenes to be preset and recalled at various control stations. Receptacle A device that provides plug-in access to electrical power. One receptacle allows you to plug in only one load at a time. Most people have duplex receptacles in their homes and offices, which are two receptacles - one over the other. If there are four places to plug in a load, forming a square, this is known as a double duplex receptacle. Romex A brand name of plastic-sheathed electrical wire that is commonly used for indoor wiring. Scene A particular grouping of lighting fixtures set at specific intensity levels that are controlled with a single switch. Scenes are common in lighting automation systems. Service The conductors and equipment for delivering energy from the electricity supply system to the wiring system of building. Everything from the power company's 'power lines' to your circuits are considered the service. Short Circuit An accidental and improper contact between two current-carrying wires or between a current-carrying wire and a grounding conductor. A short will cause a fuse to blow or a breaker to kick if they are present on the system. Switch A device that controls electrical current passing through hot circuit wires. Used to turn lights, appliances, and other loads on and off. Three-Way Switch Three-way switches are always installed in pairs and used to control a load (such as a light fixture) from two different locations. Three-way switches do not have ON and OFF marking since 'up' can be either on or off and 'down' can be either on or off depending on the other switch. These switches are usually used at the top and bottom of stairs or on either side of a room that you can walk through so that you can control the load at either location. UF (or Underground Feeder) Sunlight and water resistant wire used for direct burial in the ground and outdoor wiring. UL An abbreviation for 'Underwriters Laboratory', an organization that tests electrical devices and loads for safety. Voltage (or Volt) A measurement of electricity in terms of pressure. If you think of water flowing through a pipe instead of electricity flowing though wires, it makes sense that a large pipe can carry more water. However, a large pipe can have just a trickle of water flowing through it or can be bursting with water pressure. This is the same with electricity. Voltage is the 'pressure' of electricity flowing through a wire, regardless of the size of the wire. Most people refer to voltage as 'volts' for short. Wattage (or Watt) A measurement of electrical power in terms of total energy consumed. Wattage can be found by multipying voltage times amperes. In terms of water flowing through a pipe, we would measure how many gallons have flowed no matter what the size of the pipe or the pressure of the water. This is the same with electricity. Wattage measures the amount of electricity flowing through a wire, no matter the size of the wire or the 'pressure' of the electricity.

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