Giant explosion! Burned Wires!

[jonness]

I've been working on running remote power to my detached garage thinking I would finally be finished tomorrow. Unfortunately, it looks like I might have come to the end of the road and reached a point where I need to call in the pros. I was foolishly working on the main panel live thinking it wouldn't be a big deal to run the 2 awg ground and neutral wires to the shared ground and neutral bar lugs when I heard a loud bang and saw a bright flash of light and saw smoke coming from the panel.

It appears the screwdriver shorted one of the insulated hot wires to the neutral bus I was tightening the lug on. I realized the screwdriver was touching both points, but I figured the insulation on the wire would protect it from shorting. I suspect there might have already been a nick in the wire, and the screwdriver shaft pressed up against it while the end was touching the neutral lug. Either that or, I caused the nick while reefing on the screwdriver (probably more likely).

Fortunately, I was wearing rubber gloves an not touching anything but the plastic handle of the screwdriver, so I didn't get injured.

I've attached a picture of the wires I was connecting and a picture of the burned wires (right side edge of panel).

The entire project from start to finish has been pretty much like this. I take two steps forward and one step back. It's been a massive learning experience. This particular screwup was completely avoidable. I just got careless.

If I hire someone to fix it, will they be able to splice the burned wires within the panel without needing to run new wires in the walls? I have someone I can call but I would like to get an idea of my options prior to calling him.

 

[jonness]

Looking at the NEC, it appears it's OK to splice the Romex wires inside the panel. That said, it's probably going to look a little ugly when finished.

2017 Code Language:

N 312.8(B) Power Monitoring Equipment. The wiring space of enclosures for switches or overcurrent devices shall be permitted to contain power monitoring equipment where all of the following conditions are met:

(1) The power monitoring equipment is identified as a field installable accessory as part of the listed equipment, or is a listed kit evaluated for field installation in switch or overcurrent device enclosures.

(2) The total area of all conductors, splices, taps, and equipment at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.

 

[MBfreak]

At least one major manufacturer/builder of electrical equipment ( ABB, nowadays Hitachi/ABB) from Low Voltage to Extra High Tension ( >850 kV) parts and plants has a total ban on working on any live equipment above 24 V.
The ban includes contractors, subcontractors hired by them.

So why should you not follow their rules?

Ola

 

[mcbane]

After reading your subject line I expected to read about you shorting out the bus bars. Do that without a face shield and you need new eyes. Looks like you only smoked a 12 ga, which can fixed in the box. Maybe also wipe the soot off other wires so inspector will have fewer questions.


Sent from my iPhone using The Garage Journal mobile app

 

[californiaHank]

Looking at the NEC, it appears it's OK to splice the Romex wires inside the panel. That said, it's probably going to look a little ugly when finished.

2017 Code Language:

N 312.8(B) Power Monitoring Equipment. The wiring space of enclosures for switches or overcurrent devices shall be permitted to contain power monitoring equipment where all of the following conditions are met:

(1) The power monitoring equipment is identified as a field installable accessory as part of the listed equipment, or is a listed kit evaluated for field installation in switch or overcurrent device enclosures.

(2) The total area of all conductors, splices, taps, and equipment at any cross section of the wiring space does not exceed 75 percent of the cross-sectional area of that space.

The OP is not installing Power Monitoring Equipment. I don't understand why you would quote that section of the code.

 

[jonness]

The OP is not installing Power Monitoring Equipment. I don't understand why you would quote that section of the code.

That's the section of the code commonly cited for installing splices inside of load centers. Apparently, it's the only section of the code that mentions splicing inside of panels. See 0.23 in the following video for more info:

 

[jonness]

After reading your subject line I expected to read about you shorting out the bus bars. Do that without a face shield and you need new eyes. Looks like you only smoked a 12 ga, which can fixed in the box. Maybe also wipe the soot off other wires so inspector will have fewer questions.


Sent from my iPhone using The Garage Journal mobile app

Mcbane, you're making me feel better already. Things aren't so bad. I still have my eyes!

This is the first time I've ran a stick welder inside of a load center. It looks like I need some more practice, as I didn't get very good penetration into the metal.

I took a quick look, and there are about 10 wires pretty discolored. 3 of them appear to have deformed (slightly melted) insulation but no copper showing through. 1 wire is blown out.

Tomorrow, I'll shut off the power and clean things up a bit in order to get a better assessment of damage.

 

[Jim greengo]

At least one major manufacturer/builder of electrical equipment ( ABB, nowadays Hitachi/ABB) from Low Voltage to Extra High Tension ( >850 kV) parts and plants has a total ban on working on any live equipment above 24 V.
The ban includes contractors, subcontractors hired by them.

So why should you not follow their rules?

Ola

I didnt realize he was working inside their garage.

 

[mike93lx]

At least one major manufacturer/builder of electrical equipment ( ABB, nowadays Hitachi/ABB) from Low Voltage to Extra High Tension ( >850 kV) parts and plants has a total ban on working on any live equipment above 24 V.
The ban includes contractors, subcontractors hired by them.

So why should you not follow their rules?

Ola

Why would you expect someone to know what hitchi's policies are? And why would their policies be assumed to be applicable in a home?

 

[yatg]

Is that lug split or is it just a shadow?

 

[CoogarXR]

When I was in school, about 17-ish, our electricity class was out wiring a house. My teacher let ME do the breaker box! What a privilege, right? Well, he must have been distracted, but he told me the box wasn't live. It was. I know, I should have tested it, but you'd think when the teacher tells you something, you can believe it. That taught me to test EVERYTHING... Anyway... I digress...

I was pulling wires in, and I stripped some of them before I pushed them in (since it seemed easier at the time), and the bare ground wire hit the main lug. POW! It burned off in my hand. I didn't feel a thing. But I was temporarily blinded by the flash, and I had soot all over my face. It took me a little bit to shake that off and get back to work...

So yeah, be careful.

 

[Aceman]

If all you did was short out one of your branch circuit cables, cut the bad part out and splice in a new chunk of wire.

It's very common to splice cables in a panel, we have to do it all the time when we do service changes and the existing wiring is too short to reach the breaker locations.

Next time turn the main off or hire an electrician. This work isn't hard, but you have to be mindful of your situation.

 

[Innovate1]

If all you did was short out one of your branch circuit cables, cut the bad part out and splice in a new chunk of wire.

It's very common to splice cables in a panel, we have to do it all the time when we do service changes and the existing wiring is too short to reach the breaker locations.

Next time turn the main off or hire an electrician. This work isn't hard, but you have to be mindful of your situation.

My panel has covers for the incoming feed terminals so with the main breaker off no live terminal are exposed. Turning off the main when working in the panel is much safer even if the main lugs are exposed.

 

[rlitman]

If all you did was short out one of your branch circuit cables, cut the bad part out and splice in a new chunk of wire.

It's very common to splice cables in a panel, we have to do it all the time when we do service changes and the existing wiring is too short to reach the breaker locations.

Next time turn the main off or hire an electrician. This work isn't hard, but you have to be mindful of your situation.

+1 And check your screwdriver shaft for burrs that could have nicked the insulation.

 

[Jim greengo]

If all you did was short out one of your branch circuit cables, cut the bad part out and splice in a new chunk of wire.

It's very common to splice cables in a panel, we have to do it all the time when we do service changes and the existing wiring is too short to reach the breaker locations.

Next time turn the main off or hire an electrician. This work isn't hard, but you have to be mindful of your situation.

Exactly.

 

[Zmann]

by the "Bang,Flash,Smoke " description I expected much worse lol

welcome to the club sparky

 

[PWC Repair]

That's it??!!! My wife did better than that when she ran a 3" deck screw into the wall for hanging something and stabbed the 220v for the cook stove. Burnt charred mess inside the wall and of course the wire was banjo string tight........I had to pull a new run.

 

[BillK]

by the "Bang,Flash,Smoke " description I expected much worse lol

welcome to the club sparky

I was expecting to see a transformer hanging off a pole

 

[reader2580]

My panel has covers for the incoming feed terminals so with the main breaker off no live terminal are exposed. Turning off the main when working in the panel is much safer even if the main lugs are exposed.

You probably have the UL 67 service entrance barriers required since Jan 1, 2017. I bought a new old stock Siemens load center and mistakenly thought the panel didn't have the service entrance barriers. I ordered them from Amazon for a whole $1.50, but it turns out my load center already has them.

 

[reader2580]

My panel has wires spliced with wire nuts and the inspector never said anything. I had to upgrade existing circuits to AFCI breakers and some of the neutrals would not reach the breakers so I had to splice on more wire.

 

[vavet]

I'm glad you are physically OK. It looks like the panel and wiring can be repaired.

How's your underwear?

 

[MBfreak]

Yo
Q Why would you expect someone to know what hitchi's policies are? And why would their policies be assumed to be applicable in a home? UQ

The damage caused by electricity conducted thru the human body makes no difference to where, why and whom.
It can be lethal, and at higher current levels ( ie not in a residential situation) the flash arc temperature is usually the most devastating effect.
I mentioned the reference for claritys sake , to show how widespread rules against live line work really is.

Ignorance is bliss.

Ola

 

[Zmann]

I think we all know working in a hot panel is not safe so no need for Captain Obvious to beet anyone down, it is a calculated risk some of us take, so we do not have to reprogram our electronic devices specially the VCR

these are what I use ever since I made a calculated risk working on a hot panel and touched the non insulated screwdriver from hot lug on main to panel side ;-)

 

[nadogail]

IMHO, Can you just quietly slip heat shrink tubing over the burn insulation?

 

[jonness]

Thanks for all of your comments guys. Some of them are sobering, and others are just down right funny.

I was pretty shaken up last night by the flash, sound, and the smoke. But as it turns out the fireworks far outweighed the actual damage. Several posters' assessments were correct. Only one wire needed to be spliced. Some of the other wires initially looked melted, but it was just gunk from the bad wire that needed to be cleaned off.

I'm learning the hard way here. I've definitely learned new found respect for electricians and the work they do.

I think I'm done wiring the main panel. Does my work in the vicinity of the neutral/ground lugs look OK? The neutral wire is missing a few inches of vinyl sheathing on the end. It split off while running the wires through the conduit. I think this is OK, as I've read it is for oil resistance only, and the inner wire is actually the insulator? Is this correct?

 

[jonness]

Is that lug split or is it just a shadow?

It's a shadow.

 

[Hack Fabrication]

It's very common to splice cables in a panel, we have to do it all the time when we do service changes and the existing wiring is too short to reach the breaker locations.

When I upgraded my electrical service, I had a larger breaker box installed along with a sub panel for my garage. The electrician pigtailed most of the existing wires for the same reason.

 

[Chuckster in NJ]

GIANT EXPLOSION??? "IF" you want "GIANT" you have to witness a 26.4KV phase to phase fireworks show....... I have seen some 4160 and 2300 explosions that shake the ground and the power is amazing.

TIP! A your first mistake may be your last!...... Call a Pro!

 

[mike93lx]

Yo
Q Why would you expect someone to know what hitchi's policies are? And why would their policies be assumed to be applicable in a home? UQ

The damage caused by electricity conducted thru the human body makes no difference to where, why and whom.
It can be lethal, and at higher current levels ( ie not in a residential situation) the flash arc temperature is usually the most devastating effect.
I mentioned the reference for claritys sake , to show how widespread rules against live line work really is.

Ignorance is bliss.

Ola

My question still stands.

I am not contesting the validity of the policy at all

 

[jonness]

I woke up today with renewed vigor. I'm a day older and a lot more experienced. So I'm moving forward with the garage project.

I've completed wiring the garage panel!

 

[Jim_No_Garage]

GIANT EXPLOSION??? "IF" you want "GIANT" you have to witness a 26.4KV phase to phase fireworks show....... I have seen some 4160 and 2300 explosions that shake the ground and the power is amazing.

TIP! A your first mistake may be your last!...... Call a Pro!

The closest I have come to something like that was when a transformer on a power pole when boom and sprayed Mrs_No_Garage's car with molten sparks. Cooked the paint on the hood and cracked the windshield.

POCO tried to play hard to get until she stated she had a police report of the incident - at which they paid for repairs.

Cheers

Jim

 

[theoldwizard1]

Back in the day when "mini computers" had six 100A @ 5v power supplies and disk drives required a 10A 120V breaker, we needed "more power" !

Company union sparky said, "No problem ! We have the second panel (3 phase, 30+ circuits). We will do it tomorrow, Saturday." No way was I am going to tell my "users" at 3PM Friday that the computer will be down most of the day even on a Saturday.

Sparky says "I'll cut it over hot ! Just make some cardboard shields and tape up all of my tools."

The job got done, but I am glad I wasn't there.

 

[Bigbandguy]

I used to work in an insurance related field that involved reviewing medical records on people who had made a claim. I will never forget one on a guy who had a screwdrive slip in such a way that he got across a 240 volt panel.

It burned out a part of his brain. He could remember who he was and events from the past but could not remember talking to anyone 10 minutes ago. All of his short term memory was completely gone permanently. Stay safe out there guys, this stuff does not forgive the wrong kind of mistake!

 

[MBfreak]

BigBandGuy

+2>n on your post.
Thanks

Ola

 

[reader2580]

I used to work in an insurance related field that involved reviewing medical records on people who had made a claim. I will never forget one on a guy who had a screwdrive slip in such a way that he got across a 240 volt panel.

It burned out a part of his brain. He could remember who he was and events from the past but could not remember talking to anyone 10 minutes ago. All of his short term memory was completely gone permanently. Stay safe out there guys, this stuff does not forgive the wrong kind of mistake!

Boy, this is a good reason not to work a hot panel. I just replaced my main panel this weekend and was stupid enough to work the panel hot after all of the breakers were in place. I wanted power for the lights. I think I'll turn it off in the future.

One time at work a contractor was adding an air conditioner to our data center. Our in-house electricians couldn't figure out which circuit breaker to turn off a circuit so the contractor had to work it hot. He wasn't too happy, but he did it.