Anybody have pictures of an insufficiently braced panel?

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JDBrown

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Electrical Engineer
I'm putting some training together for my company's new engineers, and I'd like to include a photo of what can happen to a panelboard or switchboard if the AIC bracing isn't sufficient for the amount of fault current at its location. I think it would really help hammer home the lesson of why those calculations are so important. So far I haven't found anything just searching online, so I figured I'd try my luck here.

So, anybody have a picture of a panel or switchboard that was destroyed by too much fault current that they'd like to share?
 
LarryFine said:
I think he's referring to conductor lashing:

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Maybe, I've seen really high current welding cable dance around a lot as an arc is struck. I noticed that years ago when the welders were air gouging out some really heavy welds that failed x-ray. I'd seen it before with jumper cables, but nothing like that air gouging operation
 
Sorry if my post wasn't clear, it seems my terminology is out of date. I meant the SCCR of the panel/bus. When I first learned about it years ago, everybody around me called it "AIC bracing", so that's what I learned. I've seen it on panel schedules, etc. and I never heard anybody say it was wrong. Maybe it was a regional thing, or even a holdover from when the old timers who taught me had learned. Sometimes old terminology dies hard, I guess. At any rate, I appreciate the correction.

If subjected to more fault current than its SCCR, a panel or switchboard can be warped, twisted, or crushed by the resulting electromagnetic force. That's what I'm looking for photos of.

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When I had moved to Tulsa. I ask about this and they did not know what I was talking about. I ask them to read the instructions that come with the equipment.
Glad to see someone talking about it.
 
JDBrown said:
If subjected to more fault current than its SCCR, a panel or switchboard can be warped, twisted, or crushed by the resulting electromagnetic force. That's what I'm looking for photos of.
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I think that sort of thing is extremely rare. I would guess the only photos you will find are from testing labs. AFC values provided by utilities or calculated are typically very high, in my experience many times double what the actual AFC is. Then you have how rare it would be to have a bolted fault that would cause the max AFC to flow. Then there is just gettting a system capable of supplying such high fault currents that could cause catastrophic failure which is also rare. For example siemens panelboards have a SCCR of 200k. loadcenters are less, but still around 65K IIRCC. SCCR and AIC have become a "hot button" issue in the NEC and for inspectors in the last 10 years or so, but I honestly think it is overblown.
 
electrofelon said:
I think that sort of thing is extremely rare. I would guess the only photos you will find are from testing labs. AFC values provided by utilities or calculated are typically very high, in my experience many times double what the actual AFC is. Then you have how rare it would be to have a bolted fault that would cause the max AFC to flow. Then there is just gettting a system capable of supplying such high fault currents that could cause catastrophic failure which is also rare. For example siemens panelboards have a SCCR of 200k. loadcenters are less, but still around 65K IIRCC. SCCR and AIC have become a "hot button" issue in the NEC and for inspectors in the last 10 years or so, but I honestly think it is overblown.
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I agree that it's (thankfully) rare. I'm sure that's why I haven't found pictures on Reddit, etc.

I work for the utility, and I'll be training a group of new engineers (mostly straight out of college). These are the folks who will soon be calculating and providing the AFC values to you good people, and I want it clear to them from the very start that this is no place to take shortcuts.

I've got a video of an arc flash to show them (those aren't hard to find on YouTube). If possible, I'd like to show them a picture of a panel that was damaged by faulty current as well.

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electrofelon said:
IIRCC. SCCR and AIC have become a "hot button" issue in the NEC and for inspectors in the last 10 years or so, but I honestly think it is overblown.
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You should have seen the guys at The USS Fairless Works back in the 70's and 80's closing primarys with no arc flash gear. Usually after taking a shot from a bottle with a cigarette hanging from the corner of their mouth. I didn't even know what arc flash gear was then lol
 
electrofelon said:
SCCR and AIC have become a "hot button" issue in the NEC and for inspectors in the last 10 years or so, but I honestly think it is overblown.
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The NEC has address AIC, in 110.9 and SCCR, in 110.10, for some 40 years now. The biggest push came with series ratings in the late 80s. How many other NEC sections have your contractors and inspectors been ignoring?

Arc Flash and PPE have only been in the last 18 years or so.

Who doesn't want to go home at night as uninjured as when you went to work. Plumbers turn off the water and gas before most work, why do electricians work live so often?
 
Hot work on live gas line


I don't work hot when I don't have to. But sometimes it's necessary. How are you going to troubleshoot a dead circuit?
 
Joethemechanic said:
Hot work on live gas line


I don't work hot when I don't have to. But sometimes it's necessary. How are you going to troubleshoot a dead circuit?
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I didn't say they never.
Of course you need to troubleshoot live. But why do electricians pull conductors into a panelboard in the same area as exposed live line side terminals? The typical answer boils down to something about it being a hassel to deenergize the feeder.
 
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