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Old 03-15-2010, 11:09 PM   #1
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Why are switches grounded?


Just curious- if all a light switch does is interupt the hot feed in a circuit? Why do they need to be grounded?
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Old 03-15-2010, 11:42 PM   #2
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because all metal parts that might become energized must be grounded. If the yoke of the switch becomes energized, if using a plastic box, it would not trip the breaker.

since the plate screws contact that metal yoke, the screws would then be energized.

so, if you touched the screw and anything that is grounded, you get zapped.
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Old 03-16-2010, 07:21 AM   #3
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Quote:
Originally Posted by nap View Post
because all metal parts that might become energized must be grounded. If the yoke of the switch becomes energized, if using a plastic box, it would not trip the breaker.

since the plate screws contact that metal yoke, the screws would then be energized.

so, if you touched the screw and anything that is grounded, you get zapped.
You should explain that to the people that built my house *lol* I went around checking all the switches and outlets for ground... they did a good job on the outlets, but not one switch was grounded... been going around doing that myself.... ugh
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Old 03-16-2010, 10:28 AM   #4
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None are grounded in my home build 12 years ago either.

From what I understand, NEC (at least previous revisions) didn't require switches to be grounded if they were installed in plastic gang box.

That might have changed, because the notes I got back with my building permit (to finish a basement) had a note about grounding all switches.
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Old 03-16-2010, 11:09 AM   #5
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Keep in mind these products are used *everywhere* in all kinds of different situations.

So in some industrial areas or maybe a home garage there might be a metal cover plate used.

Or some fancy homes might have decorative metal cover plates used.

And then keep in mind all sorts of different people wire these things...

Someone might wire one with a bare hot conductor touching a metal electrical box to which the metal part of the switch and metal cover plate is electrically connected and they have not grounded the metal electrical box.

Or someone may not "squish" the wires in all the way and may use electrical tape rather than a wire nut and a bare hot conductor might touch a metal cover plate as the plate is "forced" down on that wire.

In these situations, a grounded switch would be an added bit of protection.

Here is a sample of the wiring jobs some people do (as found by home inspectors)...
(Warning: If you are drinking something, put it down and swallow before looking at the following pictures... )
http://www.terrylove.com/forums/show...n&daysprune=-1
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Old 03-16-2010, 11:19 AM   #6
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I've been upgrading my switches in my house
Wires have a ground, but its grounded to the metal box - wrapped around the wire & under the clamp
As I go around I have added a wire from the grounding screw to the box
I do have quite a few metal face plates in my house



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Old 03-16-2010, 12:26 PM   #7
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In Canada switches are not required to be grounded but the boxes are. The switch is screwed into the box which therefore usually grounds it anyway. Plastic boxes are rarely used around here. Food for thought.
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Old 03-16-2010, 12:33 PM   #8
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Quote:
Originally Posted by n0c7 View Post
In Canada switches are not required to be grounded but the boxes are. The switch is screwed into the box which therefore usually grounds it anyway. Plastic boxes are rarely used around here. Food for thought.
for the screw into a metal box to be acceptable as a ground, it must be listed as a self grounding device. (in the US) There is a slight difference in the construction of a self grounding device and one not listed as self grounding.
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