Electrical Terminology

Basic Terms

Using the Correct Terminology 

One of the challenges facing homeowners reading the electrical portion of the home inspection is getting the terminology right. Many times home inspectors will write in the reporting terminology that is often misunderstood or was never explained.  For a homeowner that is inexperienced or unprofessional not knowing the correct verbiage could leave the homeowner changing their mind about purchasing the home just for the lack of understanding. For example, a wire is more properly called a conductor.

Here is a list of commonly used terms and their correct usage. Understanding these terms will help the homeowner recognize improper panel wiring, especially in the case of grounded and ungrounded conductors.

Common Terminology Inspectors Use

  • hot or live wire
  • neutral wire
  • panel earth ground
  • earth or ground wire
  • ground rod
  • main (disconnect)
  • main panel
  • sub-panel
  • panel cover
  • wires to outlets
  • outlet
  • service to remote panel

More Formal Terminology or Description

  • ungrounded conductor
  • grounded conductor
  • grounding electrode conductor
  • equipment grounding conductor
  • grounding electrode
  • service disconnect
  • service or distribution electrical panelboard with a service disconnect
  • distribution panelboard without a service disconnect
  • dead front
  • branch circuit conductors
  • lighting and/or receptacle outlet
  • feeder

Ampacity

The maximum current in amps that a conductor can carry without exceeding its maximum temperature rating.

Appliance

Utilization equipment that performs a function such as clothes washing or air conditioning.

AFCI

Arc-Fault Circuit Interrupter AFCI is a device that provides protection from the effects of arc-faults by recognizing arcing and deenergizing the circuit when an arc-fault is detected. 

AWG 

American wire gauge (AWG) is a standardized wire gauge system used since 1857 predominantly in North America for the diameters of round, solid, nonferrous, electrically conducting wire. The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity. Increasing gauge numbers denote decreasing wire diameters.

AWG tables are for a single, solid, round conductor. The AWG of a stranded wire is determined by the cross-sectional area of the equivalent solid conductor. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG.

Bonded

Connected to establish electrical continuity and conductivity. 

Branch Circuit

A branch circuit are the conductors between the final overcurrent device protecting the circuit and the outlet(s).

Cabinet

A cabinet is a mounted enclosure with a swinging door.

Circuit Breaker

A device designed to open and close a circuit by non-automatic means and to open the circuit automatically when there's an overcurrent. 

Current

A measurement of the rate of flow of electricity through a conductor. Current is measured in amps.

Dead Front

A dead front is without live parts that are exposed to someone on the operating side of the equipment. 

Device

A unit of an electrical system, other than a conductor, that is intended to carry or control but not utilize electricity. Examples of devices are switches and thermostats.

Disconnecting Means

A device by which the conductors of a circuit can be disconnected from their source of supply.

Feeder

The feeder is a circuit of conductors between the service equipment and the final overcurrent device. Circuits feeding subpanels are called feeders. The conductors between two overcurrent devices are called feeder conductors. 

kcmil

In North America, conductors larger than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm². The next wire size larger than 4/0 has a cross-section of 250 kcmil.

GFCI

Ground-Fault Circuit-Interrupter GFCI is a device that protects a person by de-energizing a circuit when a current to ground exceeds the value for the device. 

Line

The line refers to the incoming power. The line side of the equipment will be where the source of the power is terminated.

Load

Load refers to the outgoing power. 

Outlet

An outlet is a point on the wiring system where current is taken to supply equipment. Examples of an outlet are receptacles, light fixtures, smoke detectors, and appliances. A switch would not be an outlet, because no current is taken at a switch. Current simply passes through a switch. 

Overcurrent Protection Device

An overcurrent protection device is set to open a circuit when the current exceeds a set value. Overcurrent protection devices are usually circuit breakers and fuses.

Panelboard

A panelboard is a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the controlling of light, heat, or power circuits, and is mounted in a cabinet, and is accessible only from the front. 

Receptacle

A receptacle is a contact device installed at the outlet for the connection of an attachment plug. 

Receptacle Outlet

An outlet where one or more receptacles are installed.

Romex®

Romex® is a trading name for a type of NM cable. Romex® is the most commonly used wiring in homes. The proper name for this cable is a nonmetallic sheathed cable. A 14/2 with the ground would contain three 14-gauge conductors: one black insulated conductor (the hot); one white insulated conductor (the neutral); and one bare conductor (the ground wire). 

Service

The conductors and equipment for delivering energy from the service utility to the wiring system of the home. 

SE and SEU Cable

SE Cable stands for service entrance cable, which is not commonly used for service cable any longer but is used for the branch circuit and feeder wiring in homes. SEU is an SE cable and the U stands for the underground. SEU cable is identified for underground use. It has a moisture-resistance covering. SEU cable will usually contain three conductors, two of which will be insulated and one will be a bare equipment grounding conductor. SE cables are jacketed with gray, sunlight-resistant polyvinyl chloride.

 


Nomenclature and Abbreviations

Alternate ways are commonly used in the electrical industry to specify wire sizes as AWG.

4 AWG (proper) could also be written as:

  • #4 (the number sign is used as an abbreviation for "number")
  • No. 4 (No. is used as an abbreviation for "number")
  • No. 4 AWG
  • 4 ga. (abbreviation for "gauge")

000 AWG (proper for large sizes) could also be written as:

  • 3/0 (common for large sizes), which is pronounced 3 aught
  • 3/0 AWG
  • #000
  • #3/0


Common wires used for electric power distribution in homes can be identified by a wire size followed by the number of wires used in the cable assembly. The most common type of distribution cable, NM-B, is generally written in the following three ways:

  • #14/2 (also written "14-2"). This is a nonmetallic sheathed bundle of two solid 14 AWG wires. The insulation surrounding the two conductors is white and black. This sheath for 14 AWG cable is usually white when used for NM-B wiring intended for electrical distribution in a dry location. Newly manufactured cables without a separate ground wire (such as #14/2) are obsolete.
  • #12/2 with ground (also written "12-2 w/gnd"). This is a nonmetallic sheathed bundle of three solid 12 AWG wires having bare ground in the middle of two insulated conductors in a flat-shaped NM-B yellow-colored sheath. The color is a North American industry standard for cables made since 2003, and aids identification.
  • #10/3 with the ground (also written "10-3 w/gnd"). This is a nonmetallic sheathed bundle of four solid 10 AWG wires having bare ground and three insulated conductors twisted into a round-shaped NM-B orange-colored sheath. The insulated conductors are black, white, and red. Some cable of this type may be flat to save copper.

 

Pronunciation

AWG is colloquially referred to as gauge and the zeros in large wire sizes are referred to as aught. Wire sized 1 AWG is referred to as "one gauge" or "No. 1" wire. Similarly, smaller diameters are pronounced "x gauge" or "No. X" wire, where x is the positive integer AWG number. Consecutive AWG wire sizes larger than No. 1 wire are designated by the number of zeros:

  • No. 0, typically written 1/0 and is referred to as "one aught" wire
  • No. 00, typically written 2/0 and is referred to as "two aught" wire
  • No. 000, typically written 3/0 and is referred to as "three aught" wire,

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