"Switch, General-Use Snap" -- What Does that Even Mean?

Question

I'm confused. I've always thought that a "Snap Switch" looked something like the thing pictured below, because the early ones made a definite snapping sound when actuated.

But an image search for "snap switch" or "General-Use Snap Switch" or "Switch, General-Use Snap" as the NEC puts it, yields results that look like this:

I've searched around on the web and have come up with differing opinions. It seems everyone has a different idea in their mind when they say "snap switch."

What type is the National Electrical Code talking about when it defines a General-Use Snap Switch as A form of general-use switch constructed so that it can be installed in device boxes or on box covers, or otherwise used in conjunction with wiring systems recognized by this Code?

Answer 1

NEC is specifying snap switches designed to fit standard enclosures or domed covers. I.E. our ubiquitous friend the "1-gang box". Separately in NEC 110.2-3, NEC requires equipment which is approved and installed according to instructions. These work together to lock out Chinesium, as well as UR-Recognized components such as your web finds.

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The definition of a "snap switch" is one that has a mechanical action to rapidly separate the contacts.

This is necessary to arrest arcing. Imagine if the user was allowed to part the contacts slowly. When it got a few microns apart, the gap would be too small to stop 120VAC or a lesser DC voltage. So the voltage would arc right on across it. This would ionize the air, and make the air more conductive - so as the gap slowly increases, the electricity would keep on arcing. Then a much larger gap would be required to extinguish it.

This problem is made much worse when an inductive load is involved, and also worse when DC is involved. If you've ever been in a very old house where the switches had a significant action and "snap" -- those date back to the switch designs used with DC power, and were required for it, or a magnetic or pneumatic blowout of some kind.*

So the switch mechanism and aesthetics are designed to at least strongly encourage a sharp snap separation of the contacts.

And our friend Technology Connections has a video on the topic, of course.

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* Magnetic blowouts work with DC power and involve a "coil" (typically only 1 or 2 turns) wired in series with the switch. When the switch is interrupted, the coil's magnetic field collapses (DC, remember) and this "bends" the arc, increasing its functional length and also pulling it into arc chutes made of insulating materials. (it's fun finding those materials - traditionally they were "hard board" asbestos which is harmless if respected; today they use ceramics but they're fragile.)

Pneumatic blowouts are used on very large relays (contactors) which are too large to operate by a magnetic coil. Here, the magnetic coil operates an air valve. When energized (on), the valve routes compressor air to a piston which overcomes a spring and throws the relay contacts. When de-energized), the valve routes piston air to a vent. The vent is aimed directly at the arc, and literally blows it out by pushing the ionized air onto an arc chute.

Answer 2

That is correct.

The push button switches are snap switch category.

When you push, the spring will eventually snap (click) into new position.