Does a snap switch have any internal wiring? If not, then the entire snap switch is part of the Premises Wiring System. Wiring doesn't have an Article 100 definition, but commonly means wires.
"Wiring" is a single word term. It is used in the body of the
NEC over 750 times, yet it is not given as an entry in Article 100 Definitions. The first place we are to look, when this is the case, for a definition of the term, is any applicable technical dictionary.
My copy of the IEEE Standard Dictionary of Electrical and Electronic Terms does not include "wiring".
My copy of the IEEE Standard Dictionary of Electrical and Electronic Terms does include "wire" and it makes an interesting statement:
If a wire is covered with insulation, it is properly called an insulated wire: while primarily the term wire refers to the metal, nevertheless when the context shows that the wire is insulated, the term wire will be understood to include the insulation.
To carry the idea of "wire" a little further, consider "busway." Article 368 describes Busway and it is included in Chapter 3 of the
NEC. And Chapter 3 is
Wiring Methods. Busway is defined:
368.2 Definition.
Busway. A grounded metal enclosure containing factory mounted, bare or insulated conductors, which are usually copper or aluminum bars, rods, or tubes.
Ah, but you might say: "Wiring Method" is a two word term, and it is not defined either.
So, let's turn back to Premises Wiring (System)'s definition:
Premises Wiring (System). Interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed. This includes (a) wiring from the service point or power source to the outlets or (b) wiring from and including the power source to the outlets where there is no service point.
Such wiring does not include wiring internal to appliances, luminaires, motors, controllers, motor control centers, and similar equipment.
Note that I did not highlight "wiring devices". I consider that a two word term to mean "devices". A simple snap switch is included as wiring. . . and, obviously, current travels through the conductors inside a simple snap switch. . . do those snap switch internal conductors look like THHN? No. With busway as a guide, I don't think they have to, to be understood as wiring.
The really interesting, challenging, mind bending hook comes in that last sentence of the definition of Premises Wiring (System). . . "Such wiring does not include wiring internal to . . . controllers. . . " (this is not about my "wanting", rather, it is about what I read in the words of the
NEC.