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#408670 - 10/19/07 09:30 PM Light switch sparks??
xssass Offline
newbie

Registered: 08/19/02
Posts: 49
Loc: Cleveland
This just happened to me as I was turning off a light, and has happened to me many times before on different wall switches, and I have always wondered why. Why does a wall light switch sometimes have a little spark on the inside as you turn the switch off? The one I just turned off, is a light switch that controls power to a socket on the outside of the house. (halloween decorations) But I have noticed this over the years on different switches in different house. I usually notice it when it is the last light off, so it is dark, and I see a VERY small "flash" inside. I see it through the little gap where the light switch is able to move back and forth. So what is that?

Thanks
TimK

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#408671 - 10/19/07 10:50 PM Re: Light switch sparks?? [Re: xssass]
RCovell Offline
Carpal Tunnel

Registered: 09/26/03
Posts: 6034
Loc: Jayhawk Land
I've seen the small flash, too. It's generally nothing to worry about as long as it stays small.

I think it's caused by the electricity jumping between the contacts, kind of like when you scuff your feet on the carpet and touch a metal surface and see the static discharge.

With house electricity, the current wants to go 'home' and will jump small gaps to do it. So, when you're closing a switch or opening one, as the contacts get close, you can get a small spark. Again, don't worry about it.

Bob.

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#408672 - 10/20/07 11:54 AM Re: Light switch sparks?? [Re: xssass]
3phase Offline
Carpal Tunnel

Registered: 09/09/02
Posts: 6849
Loc: Licensed Electrical Contractor...
As RC stated, it is normal. The light is still on till the contacts move apart enough that the arc cannot sustain itself. Arc length is dependent on voltage and current. A 120V light will have a small arc but my normal working voltage of 480V & 60-100A will have a larger arc.
_________________________
Rule of thumb,Keep your thumb from under the hammer!

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#408673 - 10/20/07 02:13 PM Re: Light switch sparks?? [Re: 3phase]
RCovell Offline
Carpal Tunnel

Registered: 09/26/03
Posts: 6034
Loc: Jayhawk Land
Boy, I bet that a spark from a 480V/100 amp service could give you quite a thrill!

Bob.

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#408674 - 10/20/07 03:55 PM Re: Light switch sparks?? [Re: RCovell]
3phase Offline
Carpal Tunnel

Registered: 09/09/02
Posts: 6849
Loc: Licensed Electrical Contractor...
Just as long as you are not too close! seriously I have seen and heard linemen throw in on a dead short. Loud noise and a very pretty light show. But it sure makes the guy holding the hotstick nervous
_________________________
Rule of thumb,Keep your thumb from under the hammer!

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#408675 - 10/20/07 09:37 PM Re: Light switch sparks?? [Re: 3phase]
xssass Offline
newbie

Registered: 08/19/02
Posts: 49
Loc: Cleveland
Thanks for responding. I kind of figured that it was not something to stress about. It was something that would always make me wonder though. I remember the first time I noticed it, was when I replaced a light switch. (early in my handyman days) I took the switch back to the store and returned it saying it gave off a spark when you switched it. Then I put in the 2nd new one. Same thing. After the third replacement, I figured, it is what it is. So thanks for the wonderment turning to knowledge. And of course, no more trips to the store

peace
TimK

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