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Mr.RC-Cam

Shorted PC Power Cord = Fire. Yikes!

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Yesterday I had a small fire mishap while sitting at the engineering workstation. It seems my guardian angel saved me from a dreadful outcome.

I was working on a CAD design when the PC's UPS backup started to randomly click (power relay noise). There's a voltage display on it and the voltage was randomly jumping up to 150VAC! My first thought was that the UPS was failing since 110VAC is used here (not 150VAC).

Then I heard some arcing noise. As I was getting up to find the source of the electrical arcing I noticed that the space between my desk and wall was glowing brightly. But since there's no light back there this was a significant WTF moment for me.

Then I saw it. A small section of the PC's power cord had sparks shooting out of it. Like a 4th of July roman candle sparkler. Major panic, followed by pulling cords from the wall socket. I was stunned, standing in a room filled with smoke.

Postmortem revealed that the PC's Chinese made "10 Amp" cord had 21AWG (0.4mm2) wire in it. This is much too small and probably illegal in the USA for AC power cord applications. On the outside it looks like it is adequately sized, but the look inside shows it is a fake 10A rated cord.

Here's a photo of the section that had started to go Chernobyl.

cord_fire.jpg

 

BTW, the building's AC mains outlet is served by a Arc Fault Protected circuit breaker in the breaker load center box. It is designed to sense arcing and automatically shut off the circuit. There was a lot of arcing and sparking, yet it did not trip!

My wife was (and still is) completely freaked out. Now she wants to pull every cord from every AC socket before bed time.

 

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Wow you would never tell just by looking. Im seeing more and more fake and dangerous stuff from China so much so that I often buy from large retailers at higher cost just to be sure Im getting the real deal. Ebay has its uses but its flooded with fakes!

 

Terry

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Yes indeed, the fake cord looked the same as a real 10A cord. But buried under all the vinyl insulation was a scant amount of copper.

Fake electrical parts are scary stuff; This was a close call and I feel very fortunate to have been sitting three feet away when it happened.

 

 

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I don't think the fire gods are finished with me yet. Today we returned home and got hit with a nasty electronic burning smell. I followed my nose to the theater room and noticed the TiVO DVR was dark. Up close I could hear a little whimpering click noise from it.

When I popped the cover the smell was quite strong in this one. There was a blackened spot on the sheet metal cover and that pointed me to the hard drive. That's when I noticed the SATA power plug had a burn hole in it. Here's a photo:

tivo_burn.thumb.jpg.52847b0fc7c56b2f962a


After testing the hard drive on a bench power supply I confirmed it was drawing correct current (not overloaded). I cut off the melted SATA power plug and soldered on a new one. The TiVO booted up and is working great again.

My wife is still freaked out about the previous flaming cable. This new incident has her convinced that we can never leave any plugs in the walls unless we are standing next to the appliance while it is powered. That horrible idea will have my attention if electrical smoke happens again.

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Those SATA plugs have always looks a little flimsy to me. The drive to make everything smaller is not helping, in fact I have often hard wired rc servo leads for greater reliability :)

 

Terry 

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This morning my PC failed to boot and it reported a warning that the WIN7 emergency repair disk was needed. But the emergency disk would hang after running for a couple minutes. Not a great way to start the day.

Because of the recent power cord incident I suspected the power supply was stress damaged (from the arcing voltage transients). I swapped it out and luckily the PC successfully booted. 

I guess this means that those pesky electrical fire gods are still messing with me. But at least they had the courtesy to skip the smoke this time.

 

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