Terminology is the vocabulary of technical terms and usages appropriate to a particular trade, science or art. Does it matter what we call something in the National Electrical Code (NEC)? Is there a difference in what something is called in the field or what a component is called in trade slang or an industry term versus the technical term?


As an Arizona electrical contractor doing an electrical installation, I needed a union for a rigid metal conduit connection to a piece of electrical equipment so the conduit could be disconnected and the equipment replaced easily. I sent an apprentice to the supply house to pick one up. He came back empty-handed and told me the counter person said they did not have a union. That surprised me so much that I called the supply house to inquire why they did not have any in stock. The counter person told me he did not have any “unions” in stock but did have “Ericksons.” He said the apprentice should learn the electrical nomenclature.


Technically, a union is a three-piece coupling intended for use with rigid metal conduit or intermediate metal conduit and is used in place of a regular coupling so the raceway can be taken apart. “Erickson” is a trade name for a union fitting. Needless to say, I was very upset with the counter person for causing a delay and an extra trip.


NEC Article 410 covers lampholders and luminaires; however, do you screw a bulb or lamp into a lampholder? Why is it called a “lampholder” in the industry and the NEC, while the major home improvement industry use “bulb”? If you ask a salesperson for lamps in a home improvement store, he or she will refer you to the table and floor lamp department. Many electricians also use the term “bulb,” but the NEC does not. Technically, regarding the nomenclature of an incandescent or fluorescent lamp, the bulb is the glass part that encloses the filament for the incandescent lamp or contains the gases in the fluorescent tubular lamps. The NEC uses the phrase “fluorescent tubular lamp” and “incandescent lamp.”


Probably the most frequent misuse of terms is when dealing with grounding and bonding. Many electricians in the field will use the term “ground wire.” Which wire does “ground wire” refer to? There are many different “wires” or, as I like to call them, conductors. When asked about specific information on a “ground wire,” most electricians will say the “green wire.”


Equipment grounding conductors can be bare, covered or insulated. Individually covered or insulated equipment grounding conductors will have a continuous outer finish that is either green or green with one or more yellow stripes. The covering of a covered equipment grounding conductor has not been tested for its insulation characteristics. A grounding electrode conductor of the wire type can be solid or stranded, insulated, covered, or bare, as the last sentence of 250.62 notes. There are many different types of grounding conductors, and then we start talking about grounded conductors, which is an entirely different issue with other rules for color coding and insulating.


Another major difference between field nomenclature and the NEC deals with photovoltaic modules, panels and arrays. Many electricians and even manufacturers use the term “panel” to describe a photovoltaic module. 


Section 690.2 provides definitions for each of these terms. A module is defined as “a complete, environmentally protected unit consisting of solar cells, optics, and other components, exclusive of tracker, designed to generate DC power when exposed to sunlight.” A panel is defined as “a collection of modules mechanically fastened together, wired, and designed to provide a field-installable unit.” An array is defined as “a mechanically integrated assembly of module(s) or panel(s) with a support structure and foundation, tracker, or other components, as required, to form a DC or AC power-producing unit.” 


Is there an issue about how these terms are used? A panel, as noted in the definition, is a collection of modules.


Wherever possible, use the correct terminology or nomenclature, especially when ordering materials. And for Pete’s sake, don’t belabor an apprentice for not knowing the relationship between common and proper terminology. A disconnect in nomenclature can cost someone time and money.