today at work

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electricalperson

electricalperson

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Location
massachusetts
today at work i was turning on circuits in a new house i wired. i turned on the first circuit i wanted to liven up and all of a sudden i see a spark shoot out and a LOUD bang. sounds like a gun shot. the breaker didnt trip but i suspect there was a short circuit and it blew it clear. there was a box that didnt have a receptacle and the ground was touching the hot conductors so im sure that was the problem. (missed that receptacle when we were putting devices in). anyone else have this happen? last time i heard a bang like that was when a circuit in a building that had FPE breakers had a short.
 
Rewire said:
I have seen this were the ground touches the hot screw on recptacles but usually the breaker trips that must be one tough breaker
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probably touched it lightly. usually when i turn on a circuit for the first time i expect something to happen like this so i stand to the side. it was so loud it made my ears ring. it was a GE breaker also. had some bad luck in the past with them
 
I'm not sure at what point in history is became customary to energize new circuits without ringing them out, but this is a practice that needs to stop. Read any old text, and they will normally alway show ringing out the circuits after ruff, and before the circuits are energized at the finish.
 
mdshunk said:
I'm not sure at what point in history is became customary to energize new circuits without ringing them out, but this is a practice that needs to stop. Read any old text, and they will normally alway show ringing out the circuits after ruff, and before the circuits are energized at the finish.
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well around here when i do extra stuff like this people say im wasting my time. but next time before i turn on a new circuit im ringing it out. i get bitched at for testing a 8/3 range cable hanging out of a wall for voltage. sorry if i made you angry:confused:
 
electricalperson said:
well around here when i do extra stuff like this people say im wasting my time. but next time before i turn on a new circuit im ringing it out.
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Yeah, it takes all of thirty seconds to put one meter lead on the ground bar and go down through all the breakers with the other meter lead. You'll get the occasional ohm reading from light bulbs and GFCI's, but you should be able to discriminate those from a hard short.
 
mdshunk said:
Yeah, it takes all of thirty seconds to put one meter lead on the ground bar and go down through all the breakers with the other meter lead. You'll get the occasional ohm reading from light bulbs and GFCI's, but you should be able to discriminate those from a hard short.
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Marc, I've never considered that, but it makes good sense. Pass me the koolaide I'm in. 30 seconds? I can do that.
 
Good idea Mark. Everyone I've worked for just flips the switch. Makes much more sense to test our work before making it live.
 
You may now have a micro-gap that was melted between conductors, and evolves into a temperature-cycling-sensitive or vibration-sensitive short because the gap is so small.
 
I ring them out.....by turning my head and flipping on the breakers.:wink:



That way you get to test the breaker too.




I will ring out big feeders. I don't want to know what a 200 amp fault sounds like.
 
220/221 said:
I will ring out big feeders. I don't want to know what a 200 amp fault sounds like.
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For feeders, I'd hope a fella would megger them instead of a quick ohm check. Particularly 480 and above.
 
220/221 said:
I ring them out.....by turning my head and flipping on the breakers.:wink:



That way you get to test the breaker too.




I will ring out big feeders. I don't want to know what a 200 amp fault sounds like.
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Bo....then harps
 
Was working on a job back when I was just starting my apprenticeship. The contractor I was working for had phases crossed in a J-box(480V feeding a large piece of shop equipment) when he turned on the breaker(without checking anything first) it was apparent where the fault was located. It's amazing how a square box can take on the shape of a cylinder right before your very eyes. I will say that from that day on I check virtually everything before power is put to it. BTW, it's saved me some expensive repairs over the last 10+ years.
 
Wow

Wow

Can't believe some others don't ohm out circuits even working only by themselves. So I guess megging might have some think I was nuts:confused:
 
nizak said:
Was working on a job back when I was just starting my apprenticeship. The contractor I was working for had phases crossed in a J-box(480V feeding a large piece of shop equipment) when he turned on the breaker(without checking anything first) it was apparent where the fault was located. It's amazing how a square box can take on the shape of a cylinder right before your very eyes. I will say that from that day on I check virtually everything before power is put to it. BTW, it's saved me some expensive repairs over the last 10+ years.
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It takes a good individual to admit one's mistakes. I can second that nizak, only once, but saved me alot of embarrasment!
 
electricalperson said:
usually when i turn on a circuit for the first time i expect something to happen like this so i stand to the side.
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Remind me not go near any of your panels. :grin: Seriously, I have always considered it good practice to stand to the side when energizing a panel, especially for the first time.

FWIW, I agree with the idea of a continuity test on a ruff..., er, rough-in. I do not do it on every job, as not every one of my installs have the wires nutted (or taped, for that matter :grin: ) all the way through.
 
I always wear my PPE when I turn breakers on....
arc-flash-ppe.jpg
 
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