snap switches

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timo said:
why are snap / toggle (light ) switches rated AC only?
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I would guess that with so little consumer need of DC snap switches that manufacturers are not paying for design and testing needed for a DC rating.

That is a total guess, take it for what its worth.:)
 
peter d said:
I was taught that a DC arc does not quench as quickly as an AC arc and will therefore rapidly burn up the contacts if they are not made to be used with DC.
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true.
zero crossing of AC will kill an arc way before a DC arc will die.
 
Are you talking about toggle type residential light switches? Because there are plenty of "snap switches" with DC ratings, they just are not the same ones used as residential light switches. DC ratings require a lot more separation distance per volt, so the average cheap household 120VAC snap switch would be limited in that way.

You can get the resi toggle switch style with a 24VDC rating, the switch body is bigger, but then the amps are lower too; 3A is the common one I've seen. But they are always momentary double throw center off , because they are used for controlling a low voltage lighting system.

Why are you asking?
 
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low v dc switches (std toggle) are also used for the thermo couple voltage for gas fireplaces (on/off switch). looks like a std switch but is rated dc to be NEC compliant. a std 120vac switch would suffice here, but not allowed due to the 120vac switches not carrying the dc rating. to be honest, the std 120vac switches can handle DC to a certain level that would not damage the contacts. they can certainly handle dc voltage up to the peak of 120vac(rms) that is ~170v, its the amps that are of concern. 1amp DC at 24v, is not an issue for a std plain 'ol 120vac toggle switch. i guess they take the guess work out of application and mandate it via UL and/or specified rating. kinda silly if you ask me, it's likely the same darn switch.
 
seems to me I have seen what looks like a standard light switch but that has a DC rating. but I agree with previous posters that the primary reason most common light switches don't have a DC rating is because it would add cost. why would you want to add 2 or 3 cents cost to a 20 cent item?
 
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