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Connecting a circuit into a live panel? Be careful! This is the result of a recent mishandling in my class recently. To make things clear, I am NOT the one who did it XD One of my classmates was inserting a NMD cable (the supply cable of a lighting circuit to be exact) through a connector into his panel. However since our teachers now ask us to work on LIVE panels (because it represents the real life), he did not pay attention to the cable's ground wire. The ground was touching the connector (which thus was to ground) and came in contact with one of the breakers busbars. This basically sent 120V to ground LOL. I happened to find the connector the last day before holidays, so I thought I could show it to you guys! You can see the connector literally melted. But that's not all! The panel itself now has a large 3" crown of black soot spikes around one knockout! I wanted to take a pic before Holidays but never got around to it LOL. Keywords: Miscellaneous

Connecting a circuit into a live panel? Be careful!

This is the result of a recent mishandling in my class recently. To make things clear, I am NOT the one who did it XD

One of my classmates was inserting a NMD cable (the supply cable of a lighting circuit to be exact) through a connector into his panel. However since our teachers now ask us to work on LIVE panels (because it represents the real life), he did not pay attention to the cable's ground wire. The ground was touching the connector (which thus was to ground) and came in contact with one of the breakers busbars. This basically sent 120V to ground LOL. I happened to find the connector the last day before holidays, so I thought I could show it to you guys!

You can see the connector literally melted. But that's not all! The panel itself now has a large 3" crown of black soot spikes around one knockout! I wanted to take a pic before Holidays but never got around to it LOL.

100_1147.JPG 20130424_170602.jpg Short_through_connector.JPG HPIM0679.JPG 20120904_150451.jpg
File information
Filename:Short_through_connector.JPG
Album name:Vince / Miscellaneous
Keywords:Miscellaneous
Filesize:278 KiB
Date added:Dec 29, 2011
Dimensions:2592 x 972 pixels
Displayed:140 times
URL:http://www.galleryoflights.org/mb/gallery/displayimage.php?pid=10092
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Comment 1 to 9 of 9
Page: 1

streetlight98   [Dec 29, 2011 at 12:23 AM]
Ouch! Shocked
joe_347V   [Dec 29, 2011 at 01:27 AM]
O_o How does the cable look like?
gailgrove   [Dec 29, 2011 at 01:44 AM]
That once happened to me, not a live wire but I tightened the clamp too much, then when I turned the power on, boom! Pretty much the same thing as here, the connector was melted and I got a bunch of black soot inside the junction box and on the joist it was attached to! You have to be very careful when working in a live panel, I've done it a few times but if it's not a huge inconvenience I'll just shut off the main, safety first!
streetlight98   [Dec 29, 2011 at 02:04 AM]
Yeah if these clamps are overtightened the insulation can be scraped off the wires. Shocked
SeanB~1   [Dec 29, 2011 at 05:25 AM]
Dropped an uninsulated screwdriver in a live panel once.......... Still have it, still has the melt marks on it.
LilCinnamon   [Dec 29, 2011 at 01:06 PM]
Oh gosh! Someone needs to learn their electricity. For a teacher shouldn't they have already learned it??
SeanB~1   [Dec 29, 2011 at 01:19 PM]
Teaching is much better absorbed if there is an element of reinforcement. You are a __LOT__ more careful if you are handling a fused and safed 120kg bomb than if you are mounting a 120kg practice bomb that is unfused. Just like you are a very cautious operator if sitting in the seat, even if the pins are in place on the ejection gun, but you are going to move a lot more if the seat is out. 120V is not soo dangerous, 230 and higher is pretty much going to hurt or worse.
FGS   [Dec 29, 2011 at 02:27 PM]
Funny thing you should upload this pic. Just this morning (less than one hour), the guy working the toy tractor (Komatsu PC 18MR) snagged the conduit feeding the garage and pulled the wires inside causing one of them to have the insulation to be ripped off at the box in the basement. Causing it to arc over to ground until the wire got cut in half. It didn't even trip the breaker (100A).

I went down there to shut it off before it shorts out (too late for that), smelled electrical fire, went to the panel and shut the breaker feeding the garage, opened the box where the wires goes into. Saw one of the three wires cut in half, some major black soot inside a gray box.
TiCoune66   [Dec 29, 2011 at 03:15 PM]
Joe: The cable turned into an ungrounded NMD Laughing In other words the ground wire evaporated! O_O

Ian: As I said in the description, the guy just forgot he was working into a live panel. A lot of my classmates are used to work in panels with the main breaker turned off. I am myself not too nervous when working around live exposed parts, I got used to it pretty fast!

Everyone: I'm going to try to get that pic of the burn marks on the panel when I get back to school!

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