Shorting - result of power surge?

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Old 08-12-14, 10:14 PM
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Shorting - result of power surge?

Tonight we had what appears to be a power surge - one power strip blew, with dark soot all over it and the carpet below. Another strip no longer works, and it appears to have a bit of soot under a wall wart. The wall wart that was plugged in still seems to work. We called the fire dept as more than 10 breakers tripped, and the smell of electrical arcing was strong. After coming over, using a heat "camera" on our walls, they felt everything was OK. They also checked out our neighbors houses, that also had the same problems.

As we were reviewing things, I jiggled a wireless router extension (basically a wall wart with a built in Wi-fi extender) plugged directly into an outlet. The lights on a *SEPARATE* circuit flickered. I was able to replicate this problem with a small USB charger.


I turned off both breakers to the two circuits, and am leaving them off.

Obviously, at this point we will be having an electrician come in, and our power company is looking into the surge (linesman said all looked OK - it would be handed over to the power quality division).


In the interim, this is bugging me. How could (what appears to be a short) effect a totally separate circuit?


(Measured voltage at the circuit, when the breaker was on, was 122.)

Thanks!

John
 
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Old 08-12-14, 10:23 PM
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In the interim, this is bugging me. How could (what appears to be a short) effect a totally separate circuit?
Remember..... a short will cause a breaker to trip. You more than likely have an open or intermittent connection.
 
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Old 08-12-14, 10:26 PM
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But inserting/removing the plug flickers the lights on a second circuit, but doesn't trip the circuit breaker or the GFCI. I'm wondering if these circuits share a common neutral. I'm not too sure they do - they are on the same side of the electrical panel (but maybe that doesn't matter).

BTW - thanks for the quick reply!
 
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Old 08-12-14, 10:30 PM
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They could very well share the neutral.
 
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Old 08-13-14, 06:09 PM
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I decided to attach a picture of the power strip:Name:  power_strip.jpg
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Size:  40.9 KB
 
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Old 08-13-14, 06:18 PM
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Power strips have at least one MOV (metal oxide varistor) that shunts excessive voltage from hot to neutral. Some of the better ones have a second MOV that shunts hot to ground. These types usually have lights on them showing a ground problem if the ground is missing.

Obviously that strip should be taken out of service and discarded.
 
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Old 08-13-14, 06:27 PM
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Oh, certainly, just thought I'd post the photo. Eventually I'll disassemble it, if I don't have to send it in.

Could the soot/smell just be the MOV blowing? The other strips (3 others) failed but no soot etc...
 
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Old 08-13-14, 06:33 PM
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The MOV's can explode or just burn open. That soot looks to be caused by the MOV and it's usually attached to the first receptacle. The MOV is the most expensive part in the strip. The better the strip.... the better and larger MOV is used.

Sample..... (a good one- yours will be black and crumbled)

Name:  mov.jpg
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