Is This Normal? (Breaker Failure)

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  #1  
Old 04-20-13, 01:29 PM
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Is This Normal? (Breaker Failure)

Today I wired up a MWBC to feed 2 circuits that were moved from the receptacle panel to the lighting panel. Being an idiot, I wired the red and black coming in together and the two blacks going out together. Put the over on the box and flipped on the breaker. I heard a loud pop, and saw a bright flash come from where the breaker attaches to the bus (Square D). It tripped the 100A breaker in the main panel and the breaker welded to the buss. Is this normal?
 
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Old 04-20-13, 01:39 PM
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I'm not sure from your description what you did, but it sounds like you may have wired a direct phase bump when you wired the red and black coming in together. It also sounds like this was in a subpanel. If that welded the breaker feeding the subpanel to the bus bars in the main panel, consider yourself lucky. The last time I remember seeing one of those in action, it blew the jacks open on the pole when the circuits were closed.
 
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Old 04-20-13, 01:50 PM
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I basically wired A phase to C phase and threw the breaker. I doubt the fuse on the pole blowing as the transformers are 50KVA.
 
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Old 04-20-13, 02:25 PM
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Defiantly not out of the norm. You had a phase to phase short. The 100 amp main saved your butt.
 
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Old 04-20-13, 03:03 PM
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I basically wired A phase to C phase and threw the breaker.
Yep. that'll do it.

I doubt the fuse on the pole blowing as the transformers are 50KVA.
The gear that the phases were butted in drew at least 2,000 amps. Probably closer to 8,000. The POCO supply was dedicated. That pole was probably 1/4 mile away, and we heard the jacks blow from inside the building.

The good news is that they saved our butt, just as the 100A breaker saved yours. We were online, full power, in less than 2 hours.
 
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Old 04-20-13, 07:23 PM
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I learned a valuable lesson from this.
 
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Old 04-20-13, 07:54 PM
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I learned a valuable lesson from this.
Yes, you did. The most valuable part of it may be that you recognize that you learned it.

BTW, I meant to say earlier that I really enjoyed hearing you say that you
Put the cover on the box and flipped on the breaker.
Today's lesson appears to be at least the second good one you've learned.
 
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Old 04-20-13, 09:33 PM
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An old boss of mine use to lecture to stand to one side when flipping a breaker on because the boxes are made to blow straight out. After once seeing a dead short on a 480 panel fused for 100 amps I believed him.
 
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Old 04-20-13, 10:07 PM
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What the heck is a 16 year-old kid doing working on a three-phase system?
 
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Old 04-20-13, 11:04 PM
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What the heck is a 16 year-old kid doing working on a three-phase system?
Learning by doing? Like the rest of us?
 
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Old 04-20-13, 11:17 PM
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After once seeing a dead short on a 480 panel fused for 100 amps I believed him.
Once, right? That's often all it takes (and should be).

When I was first starting out, I managed to become part of a dead short on one of the ungrounded phases of an 800A service. When I reopened my eyes, leaning up in a door jamb maybe 8' away, I asked the man I was helping "Did you kick me?"

"Yes."

"Um.. why?"

"Because I could see every bone in your body."

"Um..

Thank you."

That's the day I learned to respect what electricity can do. Ironically, it's also the day I came to love it, and found my calling. I just had to know how something that was totally invisible could do that.
 
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Old 04-20-13, 11:21 PM
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My point is that three-phase systems are almost universally commercial or industrial installations. Such installations rarely allow for an unlicensed person to be making any repairs or alterations. I know of no jurisdiction that would license a 16 year old, no matter how qualified he may be in theory.
 
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Old 04-21-13, 07:18 AM
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Originally Posted by Furd
I know of no jurisdiction that would license a 16 year old, no matter how qualified he may be in theory.
Welcome to Pennsylvania!


Originally Posted by Nashkat1
I just had to know how something that was totally invisible could do that.
So, when did you decide against "nuclear physicist"?
 
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Old 04-21-13, 11:58 AM
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Your answer, Nick, is a bit too cryptic. Are you telling us that Justin DOES have a license issued by the State of Pennsylvania?

Or maybe that Pennsylvania has no state licensing of electricians and leaves that task to counties and/or cities? And that Justin is licensed under one of these smaller political subdivisions?

Or maybe that the "test" for an electricians license in Pennsylvania is whether or not a person can write a check for the required fee and not have it bounce?

In my state ANYONE doing electrical work for hire MUST have a license issued by the Washington State Department of Labor and Industries. This includes residential, commercial, industrial, alarm systems, cable TV systems and data systems. All classes of licensing REQUIRE both classroom training AND work experience. Pretty much the ONLY legal way for a non-licensed person to do electrical work is limited to a homeowner working on his own single-family residence.
 
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Old 04-21-13, 12:09 PM
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In our state, two unlicensed apprentices can work directly with a licensed Journeyman/Master.

Otherwise it is the same as WA.
 

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  #16  
Old 04-21-13, 07:21 PM
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No state licensing here and the only strict licensing is in the larger metropolitan areas and that is too political for my liking. Many rural areas and small towns have licensing, but requirements are minimal. Some really small towns have no licensing at all.
 
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Old 04-21-13, 07:24 PM
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An old boss of mine use to lecture to stand to one side when flipping a breaker on because the boxes are made to blow straight out. After once seeing a dead short on a 480 panel fused for 100 amps I believed him.
When energizing new 480 volt equipment for the first time, I always recommend the electrician put on his flash suit and face shield. If I am present, I stand at least 30 feet away and never directly in front of the equipment.
 
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Old 04-21-13, 07:32 PM
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The State of Pennsylvania leaves licensing up to the township, which has no licensing. The property owner who I am working with has training and insurance.

Today's lesson appears to be at least the second good one you've learned.
I'm sure there's more to learn from this. At least I didn't weld the contacts on the contactor.
 
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Old 04-21-13, 08:58 PM
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At least I didn't weld the contacts on the contactor.
No, because the weld happened because you connected the wires in a way that prevented the power from reaching the contactor, if I understand what you did correctly. Still, that is good news in terms of downtime and materials. Contactors can be both pricey and only available on special order.
 
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Old 04-22-13, 06:03 AM
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No, because the weld happened because you connected the wires in a way that prevented the power from reaching the contactor, if I understand what you did correctly. Still, that is good news in terms of downtime and materials. Contactors can be both pricey and only available on special order.
The contactor feeds the subpanel. IIrc, it was about 150 bucks and took 2 weeks to get here. Definitely long enough to ruin business for quite a few days.
 
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Old 04-22-13, 09:09 PM
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The contactor... was about 150 bucks and took 2 weeks to get here. Definitely long enough to ruin business for quite a few days.
Oh yeah. You can thank the 100A breaker and the quick weld again. I'm guessing you were able to clean up the buses?
 
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Old 04-23-13, 05:35 AM
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I'm guessing you were able to clean up the buses?
I was able to sand it and I applied noalox to prevent corrosion.
 
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Old 04-23-13, 05:52 PM
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I wouldn't recommend Noalox for use on copper bus. You originally stated this was a Square D panel, was it a QO series loadcenter or a NQOD or similar Square D panelboard? The QO series loadcenter has standard tin plated copper bus, but an NQOD panelboard could have either copper or aluminum bus, aluminum is standard. To prevent corrosion on copper bus I'd recommend a product like Kopr-Shield.

http://www.tnb.com/ps/fulltilt/index.cgi?part=20131879

Noalox is basically for aluminum connections.

Noalox Anti-Oxidant Compound
 
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Old 04-23-13, 10:03 PM
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I luvs me some Kopr-Shield. It has literally saved the job when modifying older switch gears, cabinets and other enclosures with solid copper buses installed.
 
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Old 04-24-13, 09:42 AM
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It's a QO with a copper buss. Looks like I'll be picking up some Kopr-Shield today.
 
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Old 04-24-13, 07:03 PM
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Kopr-Shield isn't cheap and few supply houses stock it in my experience, but it's worth ordering.
 
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Old 04-24-13, 08:20 PM
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Wow that stuff was expensive...
 
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Old 04-24-13, 09:14 PM
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Anyway, here is the finished product. Both panels are new and the MC is my new work.
 
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Old 04-24-13, 09:21 PM
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That looks pretty good, Justin. My inspectors would flag the exposed, unprotected light bulb, the liquidtight resting on the corner of an enclosure, and the MC laid across itself, but they're kinda picky.

Is that hub or nipple or whatever it is between the two panels just sitting there or is it connected into the trough?
 
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Old 04-25-13, 05:19 AM
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That looks pretty good, Justin. My inspectors would flag the exposed, unprotected light bulb, the liquidtight resting on the corner of an enclosure, and the MC laid across itself, but they're kinda picky.
So, I need to install a cage around the bulb, and support the seal-tite. I doubt any inspector around here would have a problem with the MC cable.

The nipple is sitting there. There are also a few breakers laying around, but they missed the camera.
 
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Old 04-25-13, 02:56 PM
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So, I need to install a cage around the bulb, and support the seal-tite.
Yes. One of those outdoor fixtures with the jelly-jar globe and the cast metal cage over that would work well there, IMO, if you don't have something else in mind. Maybe one of the 90[SUP]o[/SUP] ones, with the globe sticking up to get it out of the way? Or a straight-out one.

I doubt any inspector around here would have a problem with the MC cable.
OK, heard that.

I'm just curious though. It's too late to change it now, but why didn't you just take the closest cable in the set between the two panels into the top hole and the next one into the next one don and so on. It isn't just about aesthetics, y'know. If we did that on a job, I'm pretty sure we'd get an earful about EMF interference and overheating and yada, yada... Just so we might think the inspector had a real reason.
 
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Old 04-25-13, 03:30 PM
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Originally Posted by Nashkat1
It's too late to change it now, but why didn't you just take the closest cable in the set between the two panels into the top hole and the next one into the next one don and so on.
I was going to bring up the very same thing with him when he showed me personally, but I was wondering about the bend radius that would be involved in having them flat-routed. I always like MC bent less, rather than more.

I would have also used a standoff bracket for the box/fixture so the MC could be run underneath it and not have the "issue" with the cable coming from the righthand PB, but that's just me.

(at the very least, I would have left the cable in question loose, and installed it last, as a matter of future convenience)
 
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Old 04-25-13, 04:40 PM
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Nick, you need to delete some items from your PM folders.
 
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Old 04-25-13, 04:58 PM
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I was going to bring up the very same thing... but I was wondering about the bend radius that would be involved in having them flat-routed. I always like MC bent less, rather than more.
I agree, in general. I hate it when I pop the casing trying to squeeze in a bend. I actually wondered how that might come into play, but decided to see if Justin came back with it.

I would have also used a standoff bracket for the box/fixture so the MC could be run underneath it and not have the "issue" with the cable coming from the righthand PB, but that's just me.
Not just you. That sounds like a sweet solution, in fact. I'm imagining the cables could have come into the top of the PB then. That makes me wonder, though, how long the nipple connecting the box to the left hand PB would have had to be, and how far up the wall that would have pushed the J-box.

There are always trade-offs, aren't there?

Justin, do you have enough slack in the conductors in the seal-tite to add a coupling and a chase nipple to back the 90[SUP]o[/SUP] connector away from the 12 x 12? I'm guessing that's where the contactor is, right?
 
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Old 04-25-13, 05:56 PM
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My inspectors would flag the exposed, unprotected light bulb, the liquidtight resting on the corner of an enclosure, and the MC laid across itself
I don't like the location of the light bulb, guard or not. I think that technically the liquidtight should be supported, but the MC cable, in my opinion, is fine. I don't think there are any code issues that I can think of with Justin's installation of the MC cable.
 
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Old 04-25-13, 06:02 PM
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Originally Posted by Nashkat1
Originally Posted by Nick D.
I would have also used a standoff bracket for the box/fixture so the MC could be run underneath it and not have the "issue" with the cable coming from the righthand PB, but that's just me.
Not just you. That sounds like a sweet solution, in fact. I'm imagining the cables could have come into the top of the PB then. That makes me wonder, though, how long the nipple connecting the box to the left hand PB would have had to be, and how far up the wall that would have pushed the J-box.
I should sketch up what I'm envisioning, it's quite something else... though I'd like to see more of the run above the backboard to see what could really be done.

Maybe Justin could hire me as a designer/aesthetician?

(and I was wondering what to do about my PMs.... I can only store 13!?!?)
 
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Old 04-25-13, 06:45 PM
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I'm just curious though. It's too late to change it now, but why didn't you just take the closest cable in the set between the two panels into the top hole and the next one into the next one don and so on. It isn't just about aesthetics, y'know. If we did that on a job, I'm pretty sure we'd get an earful about EMF interference and overheating and yada, yada... Just so we might think the inspector had a real reason.
I'm not really sure what you're saying here.

I would have also used a standoff bracket for the box/fixture so the MC could be run underneath it and not have the "issue" with the cable coming from the righthand PB, but that's just me.
I like that idea.

Justin, do you have enough slack in the conductors in the seal-tite to add a coupling and a chase nipple to back the 90o connector away from the 12 x 12? I'm guessing that's where the contactor is, right?
Sadly, there's no slack. This enclosure does contain the contactor.

I don't like the location of the light bulb, guard or not. I think that technically the liquidtight should be supported, but the MC cable, in my opinion, is fine.
I was thinking of replacing the bulb altogether with whats pictured below, and I figured the perfect solution for the seal-tite.
[ATTACH=CONFIG]11921[/ATTACH]

I should sketch up what I'm envisioning, it's quite something else... though I'd like to see more of the run above the backboard to see what could really be done.
Please do! As for behind the backboard, its concrete and stone.
 
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Old 04-25-13, 08:55 PM
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Nash was saying, in so many words, that you could(?) have laid out the MC from the left PB so that it didn't run over itself, like you have it doing. That's what I was talking about with the bend radius(es).
 
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Old 04-26-13, 09:43 AM
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FYI... the reason Kopr-Shield is so expensive is because it is a colloid of copper. A colloid generally requires that the substance or element be in particles no larger than about 1 micron, or 10,000 angstroms, and may be as small as 10 angstroms, which would mean clumps of not more than a few atoms. The process of creating high-purity metallic colloids is somewhat lengthy and fairly expensive.

Easy reference: Each strand of hair on your head is about 100 microns wide. The particles of copper in Kopr-Shield are most likely going to be at least 100 times smaller, and could be up to 100,000 times smaller.
 
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Old 04-26-13, 11:31 AM
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Nash was saying, in so many words, that you could(?) have laid out the MC from the left PB so that it didn't run over itself, like you have it doing. That's what I was talking about with the bend radius(es).
Yeah, I should've did that.
 
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