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| Subject - Electrician or Fireman | |
| David Hyatt |
Last night I was watching a movie when there was a knock on my door, it was the neighbor a few doors down, saying come quick David my panel is on fire. I jumped in the truck and went there pulled the meter and began removing panel cover. The 200 amp main breaker was melted and a hole as big as my first behind it burnt through the panel can. I can't figure how this happened. The main breaker outside didn't trip so I figured it was not an overload. My theory is a loose connection but how would it burn or blow a hole in the back of the panel? Any ideas? |
| JimmyDee | Once it starts to arc and gets the air ionized around it, it must have found a pat to the other hot. Once that happens, a short will occur similar to an arc welder with no amperage control. The amperage is usually lower than a dead short but not much. Without the breaker tripping it will burn itself clean. You know the rest of the story. Jim |
| lctrc789 | I agree with Jimmy here on this one. A breaker doesn't always trip because of a loose connection or arcing and many times the bus and the breaker do not make a good connection or are arcing and that causes them to just get hot and burn. I have seen this on many ocassions and it is unusual but it does happen. Think of it this way say some one has a small lamp cord plugged in to a electric heater and the cord gets hot and burns and the breaker doesn't trip. WHY/ because the cord may be rated at 6 or so amps and the breaker is rated at 15 or 20 the cord just burns and the breaker doesn't always get the load it needs to trip. You did the right thing PULL THE METER and shut it down. You probably saved them a house fire and maybe even their lives. Good job |
| zol_man | Glad to hear you are ok. how big was the arc flash pulling a meter out under such a load? i flashed myself in the past when i didnt shut everything down and pulled the meter. |
| JimmyDee | Just curious David, Al service wire feeding the panel? Jim |
| Ryan_J | The expansion coeffiecient of copper buss is 64,000. This means that under explosion it expands to size of 64,000 times its original size. Imagine the amount of energy something like that (at 35,000 degree F, by the way) will generate. For comparison, think of a popcorn kernel exploding...its expansion coefficient is about 1,500. WOW |
| zol_man | how many of you are aware of NFPA 70? New regs for electricians, working space around energised parts, clothing,etc. |
| Ryan_J | Zol...I think you mean the NFPA 70E, not the 70. The 70 is the NEC. But on that topic, who adopts the NFPA 70E, and better still, who enforces it? |
| zol_man | you are correct, will get the info when i get back to the office tomorrow. also will require non-conductive tools |
| JimmyDee | Any electrician that wares anything but cotton clothing while on the job is a very foolish individual. I have a friend that was in a switch gear meltdown and they had to surgically remove his nylon/polyester sweatshirt because it was melted and bonded to his body. He is alive but is skin graft from his belt line to the top of his head. Contact lens are the same way. Do Not!!! Jim |
| lctrc789 | You are right about the clothing, and when I went to school and was learning about switchgears and distibution theory a few years ago, they was telling us that the flash from electrical energy is as hot as the surafce of the sun for a second, now that is very hot. |
| David Hyatt | Aluminum wire. All is fine now, panel has to replaced. I found out the main has been sizzling for a while, very hot to the touch that night, so they decided to go party and would deal with it later (The parents) the kids was who and came got me. |
| JimmyDee | Aluminum wire. I'm sure the installer saved a few bucks on that job. Do them a favor and replace it with copper for them David. Jim |
| David Hyatt | I AM NOT DOING ANYMORE FAVORS, THEY ARE MAD AT ME FOR CUTTING THE WIRE AND REMOVING THE PANEL. TRY TO HELP AND IT BACKFIRES. THE FIREMAN SAID I PROBABLY SAVED THE HOME FROM BURNING DOWN, GO FIGURE. |
| Ryan_J | Incerdible. No good deed goes unpunished :( |
| Pierre Belarge | David Don't let their ignorance ruin the fact that you performed a great deed for their family - the fact they went out and left the kids home says something about them, all the while knowing some kind of problem already existed. The arcing fault that created the situation you experienced is exactly what the Arc Fault Breakers are supposed to protect against, and regular MCCB cannot protect. The Arc is intermitent and very hot. As time progresses, the arc gets worse and more heat is developed until WHA LA you have a melt down. Loose terminations are the cause of most electrical fires. Pierre |
| frenchelectrician | i dont know if this idea will work here or not in usa area i wish there is a AFCI/GFCI main breaker for it. something simuiar what we have in European areas we have RCD's aka GFCI's and i belive it will really prevent alot of hevey arc faluting there and cut down numbers of house really get on fire something like that merci, marc p.s. i think the debate was show up in one forum some time back i dont rember where it was but that the general idea we can advoid the mess but i know the cost can be pretty steep but if that help to keep the house fire down i belive it can help a bit |
| odie | David Just a question? Did the panel inside have a ground wire to the out side disconnect or was it just bonded inside? Odie |
| Pierre Belarge | Merci Marc!!!  Happy New Year. I have not heard from you in a while, I trust all is well?Pierre |
| frenchelectrician | Pierre: i am doing fine and little busy so far with my work and i wondering about the idea about useing sorta of like GFCI or AFCI for main breaker useage i belive it can konck down a bit of damage fast there let me know what you think about this Merci , Marc |
| David Hyatt | It was a 4 wire, Odie. |
| Wirenutz | quote: makes too much sense, and too little profit doesn't it? ~W~ |
| stedder | "My theory is a loose connection but how would it burn or blow a hole in the back of the panel? Any ideas?" I had a GE breaker over heat on one leg only so badly that it burned itself through the bakelite, when I went to check the "main trip" problem I was able to reset the main and as I turned on the circuts one at a time it took about three minutes before that side of the MB was too hot to touch (still didn't trip) the load was NOT unbalanced. Was able to run and get a new main and after installing all was and still is fine (4-5 years) it ended up that the MB was just bad, poorly made stamped Made In Brazil, the new main actually said Made In USA (not that it really matters). Same thing may have been true for your situation except there was no initial trip that caused alarm. (in this case the older woman living in the house was on Oxygen) and there was more cause for alarm. |
| David Hyatt | Well I got roped into fixing this job. I cut the wires above and below the panel. Say about 6 pieces of Romex from the top and from the bottom. 4/0 aluminum feeder from the bottom. What I was thinking of doing is putting a large j-box above and below the panel to extend my wires to the panel. It can't be more than 4 inches deep to fit into the wall, how do I figure how large of a box to use? I was also thinking of splicing the feeder in a 12x12x4 in j-box. Is this legal to do? I will make sure there is access to the boxes I install. Give me your ideas on the best way to do this. |
| Wirenutz | sure.... 314.16 (last sentence) kicks you up to 314.28 per 314.28(A)(2) (also last sentence) transpose 4/0 cable to raceway (note it doesn't say which raceway to use....) ~W~ |
| David Hyatt | So the splice on the feeder conductor will work in a 12x12x4 in box. What about the size box of the juntions of romex?? If I have 10 pieces of 12/2 in the box how big shall the box be? 24 times 2.25= 54 cubic in box? What size box would that be??? Can't be more than 4 inches deep? |
| David Hyatt | You may also use the following method of calculation if you don’t have a Code book, are using a size of steel box that is not listed in chart NEC Article 314.16.A, or you are using a plastic or fiber box. If you are using a type of box that is not listed in the NEC Chart 314.16.A, then you must measure the inside dimensions of that box whether a device box or a lighting fixture style box or even a junction box that has all the same size conductors and the same type insulation and all conductors are smaller than 4 awg conductors, then multiply the height, times the length, times the depth of the box to find the cubic inch capacity of that box. This was what I was looking for I found it on another site. I thought that height x length x dept was cubic in but when I looked at the chart in the NEC the measurements did not equal the cubic in allowed. It was less. Check it out. |
| Wirenutz | moulded corners Dave, some sparky somewhere decided to calulate cubic displacement be the fill method instead of the measurement method.....thus the birth of the particular chartyet, that's all #4 and down, not your 4/0.... ~W~ |
| John A. Peters | I guess you had to cut the romex and feeders because they were damaged by the heat, is that right? Can you not lower the panel and only put a junction on the top? Do they have power in the mean time? |
| David Hyatt | I raised the panel to put J-boxes at bottom. I looked closer today at the job, I now plan on putting two boxes below the panel one containing the feeder splice and the other about 8 circuits. No power in 2 months. |