Defective switch or a bigger problem?


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Old 06-24-17, 06:43 AM
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Defective switch or a bigger problem?

My office room has been wired recently for 20Amp - all outlets and 1 switch which controls only ceiling lights are all Spec Grade 20Amp rated.
All Romex 12/2.

Recently I noticed that while turning off lights..i think I saw a arch / flash inside the switch box.
Wasn't happening often and never was sure if it was just reflection or something imagined but being rather concerned AND because recently my Computer UPS would trip for a second while turning the lights on...I opened the box.
This is what I don't understand:
The wires were securely connected - no play...no contact between wires...
The switch was warped once with electrical tape which had burned hole where Neutral (White) was connected to the terminal.
I took the switch out and in fact there seemed to be some sort of reaction on that terminal (oxidation / burned tape??)
The wires look good coming into the box.

For now I replaced this switch with another brand new....but want to learn if this could have been caused by something else??

Also...anything I can test with a multimeter ?

Thank you

PS: This time I am NOT putting electrical tape around the switch screws.
 

Last edited by PaulSC; 06-24-17 at 07:08 AM.
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Old 06-24-17, 06:53 AM
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Arcs are cause either by a loose connection or a bad contact. Why switch was wrapped in tape I have no idea. Sounds like a bad switch in your case. I just thought of one other cause is the switch is loose in box and moved to side, Wires contacted side of box. Maybe reason for tape.
 
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Old 06-25-17, 06:26 AM
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Many people will wrap devices with tape so there will not be accidental contact between the screws and a metal box. The burn mark could have been when the switch was installed and the tape didn't the job.

Any time you make a break an electrical connection with a load on the circuit you will get an arc. However, with a single room I would expect this to be a small arc and not able to be seen with a cover plate installed.

The switch was warped once with electrical tape which had burned hole where Neutral (White) was connected to the terminal.
I hope the white you have is a switch loop and you only have 2 wires (plus ground) in the box. Otherwise you are switching a neutral which is not good.
 
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Old 06-25-17, 06:33 PM
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Added the pics of the switch....

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Old 06-25-17, 06:41 PM
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I will have to inspect the box up in the attic where I know there power comes in and splits to outlets and the light / switch..... I don't know if the neutral is being switched....since I don't see the black tape on the white wire end.
But wouldn't the outlets on this circuit show an issue....I remember testing them with that special device that shows various possible issues with different lights.
 
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Old 06-25-17, 07:03 PM
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I don't know if the neutral is being switched....since I don't see the black tape on the white wire end.
If you use a meter and measure between the white and ground and get 120 volts, it is a hot and not a neutral.
 
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Old 06-25-17, 07:06 PM
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That looks like residue form the tape not burn mark. But the picture is too low of resolution to be 100% sure.

What you have there is a switch loop. Technically the white wire should been marked with a black tape, but I have never seen it done.

I only put tape around switches or outlets if they will not be installed in the junction box for a while (ie. during construction before putting drywall or tile).
Some people do it when they are being installed in metal junction box. There really is no point in taping when it is installed in a plastic junction box and on a remodel junction box.
 
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Old 06-25-17, 07:07 PM
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That is definitely a switch loop in the picture. The box is plastic so no reason for the amateur's tape job.
 
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Old 06-27-17, 06:33 PM
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Guys - so I used a Volt meter.....I am getting 120V when connecting white to ground in OFF position with black showing 0V and when in ON position - I get 120V at neutral and hot....

I will need to go to the attic and open up the box where the power comes in and splits to outlets, lights and the switch.... clearly something isn't right
 
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Old 06-27-17, 07:08 PM
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I get 120V at neutral and hot....
That is NOT neutral. It was explained as a switch loop. Hot comes down on the white wire and gets switched back up on the black wire.

That is a perfectly normal type of setup.

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Old 06-28-17, 02:20 AM
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What you have is a very common practice and if it works its safe and legal. If the switch is off and you test from white to ground you should get 120 and then test from black to ground and you should get nothing. Make sure the switch is off because if it's on while testing you will get a fulse read because it's under load so you can't tell what wire is actually feeding the sw so turn it of and test. It is just fine as long as it works. One last thing, a circuit under a heavy load can arc(spark or flash) chances are you didn't see that in this case but if you did it's only because of load like turning on your vacuum cleaner then plugging it in the wall, it will arc and it's normal. I hope this helps
 
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Old 06-28-17, 06:38 PM
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thanks - I misunderstood the reply by Tolyn ....I didn't know what it means to switch neutral and thought he meant that if Neutral is hot then it is in fact being switched.....which as said - it's not good.
 
 

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