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| 05 May 2008 11:21:09 |
| emilio_estevez |
| Changing Breaker Box - Looking for Different Perspective |
My question came up when a friend of mine asked if I could change out his Federal Pacific breaker box to a newer, safer one. My background is in industrial controls and I don't normally deal with power at the service level. I only have about two years experience so as I am now trying to learn more on my own, I'm finding a lot of things that don't add up. I started by doing some research to see what it would take to change out a breaker panel in a house without turning off the service power. It seems to me that it would not be any different getting shocked by one of the mains than it would be to get shocked by the 120V at an outlet. Each incoming line is 120V to ground (the same as the power at a receptacle) and my body's resistance to ground would be roughly the same. And according to Ohm's Law, the current that would go through my body would be the same. I don't understand the difference. Now obviously I don't plan on attempting this if the risk is actually as serious as i've read, and I do realize that even very low voltages can kill you if the current is high enough (would normally have to break through the skin and into the blood stream where resistance is very low), but the question still remains. Am I missing something? I've read that if you touch either incoming service line that you will most certainly die. Is that just to scare people that don't know enough about what they're doing into hiring someone? Lastly, I would like to point out that I work on a regular basis around 480V / 240V and am quite frankly, scared of being shocked, and I take every precaution available (which normally entails shutting off the power at its source) before working around any live circuits. I also understand that even 120V can definately be deadly, even at a receptacle. I only used that as an example because I know people will often change them without killing power. I'd like to leave this topic as purely hypothetical. Simply an example to learn from. Thanks. |
| 05 May 2008 12:06:23 |
| Tim Wescott |
| Re: Changing Breaker Box - Looking for Different Perspective |
emilio_estevez wrote: > My question came up when a friend of mine asked if I could change out > his Federal Pacific breaker box to a newer, safer one. My background > is in industrial controls and I don't normally deal with power at the > service level. I only have about two years experience so as I am now > trying to learn more on my own, I'm finding a lot of things that don't > add up. > > I started by doing some research to see what it would take to change > out a breaker panel in a house without turning off the service power. > It seems to me that it would not be any different getting shocked by > one of the mains than it would be to get shocked by the 120V at an > outlet. Each incoming line is 120V to ground (the same as the power > at a receptacle) and my body's resistance to ground would be roughly > the same. And according to Ohm's Law, the current that would go > through my body would be the same. I don't understand the difference. > > Now obviously I don't plan on attempting this if the risk is actually > as serious as i've read, and I do realize that even very low voltages > can kill you if the current is high enough (would normally have to > break through the skin and into the blood stream where resistance is > very low), but the question still remains. Am I missing something? > I've read that if you touch either incoming service line that you will > most certainly die. Is that just to scare people that don't know > enough about what they're doing into hiring someone? > > Lastly, I would like to point out that I work on a regular basis > around 480V / 240V and am quite frankly, scared of being shocked, and > I take every precaution available (which normally entails shutting off > the power at its source) before working around any live circuits. I > also understand that even 120V can definately be deadly, even at a > receptacle. I only used that as an example because I know people will > often change them without killing power. > > I'd like to leave this topic as purely hypothetical. Simply an > example to learn from. _I_ turn the power off when I'm working around 120V. It won't always kill you when you touch it, but I hate that tight feeling in my chest for the hour or so after the 'event'. Consider that when you're changing that 120V socket you're playing with 120V and ground on wires no bigger than 12 gauge, in a fairly well controlled environment. With the breaker box change, you're wrestling with 4 or 2 or 0 gauge wires, the pair of which have 240V between them, which have to be threaded out of one box, threaded into another, possibly trimmed and certainly bent to new shapes. And what if they're six inches too short and you need to run new ones? Add to that the fact that these wires are fused for 100A or more, so even if you don't electrocute yourself you run the risk of one hell of an arc if you short them together. Me? I'll wimp out and call the power company to have the mains turned off. And when they tell me they won't turn things back on without an inspection I'll think of my homeowner's insurance and say 'yea verily and thank you'. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html |
| 06 May 2008 14:54:22 |
| bud-- |
| Re: Changing Breaker Box - Looking for Different Perspective |
emilio_estevez wrote: > My question came up when a friend of mine asked if I could change out > his Federal Pacific breaker box to a newer, safer one. My background > is in industrial controls and I don't normally deal with power at the > service level. I only have about two years experience so as I am now > trying to learn more on my own, I'm finding a lot of things that don't > add up. > > I started by doing some research to see what it would take to change > out a breaker panel in a house without turning off the service power. > It seems to me that it would not be any different getting shocked by > one of the mains than it would be to get shocked by the 120V at an > outlet. Each incoming line is 120V to ground (the same as the power > at a receptacle) and my body's resistance to ground would be roughly > the same. And according to Ohm's Law, the current that would go > through my body would be the same. I don't understand the difference. > > Now obviously I don't plan on attempting this if the risk is actually > as serious as i've read, and I do realize that even very low voltages > can kill you if the current is high enough (would normally have to > break through the skin and into the blood stream where resistance is > very low), but the question still remains. Am I missing something? > I've read that if you touch either incoming service line that you will > most certainly die. Is that just to scare people that don't know > enough about what they're doing into hiring someone? > > Lastly, I would like to point out that I work on a regular basis > around 480V / 240V and am quite frankly, scared of being shocked, and > I take every precaution available (which normally entails shutting off > the power at its source) before working around any live circuits. I > also understand that even 120V can definately be deadly, even at a > receptacle. I only used that as an example because I know people will > often change them without killing power. > > I'd like to leave this topic as purely hypothetical. Simply an > example to learn from. The hazard is not just shock. If you short the hot wire to hot, neutral, or ground you will get a current of maybe 2,000A up to 10,000A. That makes things like screwdrivers evaporate. Worse, they evaporate onto your face. Added to the fun is that the transformer protection may allow the fault current for an extended time. You -really- don't want to change the panel with the wires 'hot'. If you work around 480 you should have some familiarity with 'arc flash'. An electrician might pull the meter. If you do, you have to be able to be sure that kills the power. The utility company may take a real dim view of cutting their seal on the meter. You better plan on telling them, in advance. And service panels have some unique features, like N-G bonding and grounding electrodes. Also maybe aluminum wire. Another problem is what you do if the wires are too short for the new panel as Tim wrote. I have read (but do not know) that Cuttler Hammer has replacement 'guts' for FPE panels. -- bud-- |
| 08 May 2008 19:04:58 |
| Dave |
| Re: Changing Breaker Box - Looking for Different Perspective |
"emilio_estevez" <poguen@gmail.com > wrote in message news:34803565-2327-4a43-9b90-d7d7369139a1@e53g2000hsa.googlegroups.com... > My question came up when a friend of mine asked if I could change out > his Federal Pacific breaker box to a newer, safer one. My background > is in industrial controls and I don't normally deal with power at the > service level. I only have about two years experience so as I am now > trying to learn more on my own, I'm finding a lot of things that don't > add up. > Dude, don't go there. Have you ever heard of anyone changing out their own breaker panel, much less doing it live? No? Huh, wonder why that is? The power that'll slam into you through 0 or 2 ga wire is HUGE and UNFUSED... thousands of amps. The transformer on the pole has overload protection, but it won't kick in until WAY after you're dead. What you are considering is RIDICULOUSLY DANGEROUS. Trained professionals don't do it. |
| 09 May 2008 03:52:55 |
| Paul E. Schoen |
| Re: Changing Breaker Box - Looking for Different Perspective |
"Dave" <dspear99ca@yahoo.com > wrote in message news:u9IUj.1150$Yp.150@edtnps92... > > "emilio_estevez" <poguen@gmail.com> wrote in message > news:34803565-2327-4a43-9b90-d7d7369139a1@e53g2000hsa.googlegroups.com... >> My question came up when a friend of mine asked if I could change out >> his Federal Pacific breaker box to a newer, safer one. My background >> is in industrial controls and I don't normally deal with power at the >> service level. I only have about two years experience so as I am now >> trying to learn more on my own, I'm finding a lot of things that don't >> add up. >> > Dude, don't go there. Have you ever heard of anyone changing out their > own breaker panel, much less doing it live? No? Huh, wonder why that > is? > > The power that'll slam into you through 0 or 2 ga wire is HUGE and > UNFUSED... thousands of amps. The transformer on the pole has overload > protection, but it won't kick in until WAY after you're dead. > > What you are considering is RIDICULOUSLY DANGEROUS. Trained > professionals don't do it. You are right about that. The transformer is only fused at the primary to protect it from overloads and malfunction, and many of these "pole pigs" are 50 kVA or more. This means that a 120 VAC line to neutral or earth current of 500 amperes would just start to make the fuse notice, and the instantaneous current could be as high as 5000 amps (half a MegaWatt) for a few cycles. Certainly enough to create a huge fireball and hurl globs of molten copper and steel at the unfortunate amateur electrician who just happened to let a scredriver slip across the mains. A friend was working with another experienced test technician, doing routine breaker testing in a large facility. Most of the switchgear was disconnected, but the other test technician had to do some work in the main fuse box, which I think was a 480 VAC feeder with heavy bus bar, probably rated at 2000 amps or more. I think he had to tighten a bolt, and normally he would have used a wrench that was mostly insulated with rubber tape, but he was probably tired and in a hurry, and somehow the wrench slipped and landed across the live bus. My friend saw it happen, and turned to the side just as the fireball erupted, and it burned much of his face and body. The technician who was responsible was badly burned, and soon died from his injuries. Here is a website with some images and movies of actual electrical arc blasts so you can see the "potential" for danger: http://205.243.100.155/frames/longarc.htm.Note that one of them is "only" 480 VAC. Actually, I changed out the old breaker box in the house where I now live, but I was completely remodeling it, and I had the utility company come out and pull the meter. I had a separate feeder from my other house next door, so I could provide temporary power. I actually located the new box on the other side of the wall, next to the meter, inside an enclosed porch, and I routed the 100 amp service cable into the new box while it was totally dead. Even so, I treated it with respect, and I taped the exposed conductors while I relocated them, and removed the tape only when I could safely connect them to the main 100 amp breaker. It was several years later that I was able to finish the bulk of the work, and I was able to have BGE come out and replace the meter. I had tested the installation beforehand by patching the other supply onto the mains, and I checked carefully for any loose strands of the incoming service cable. Even so, I was a bit nervous when the meter was reinstalled, but at least I had a main breaker directly on the incoming line. The old breaker box did not have a main breaker. More information and videos: http://www.lanl.gov/safety/electrical/ Paul |
| 09 May 2008 14:24:44 |
| Michael A. Terrell |
| Re: Changing Breaker Box - Looking for Different Perspective |
Dave wrote: > > "emilio_estevez" <poguen@gmail.com> wrote in message > news:34803565-2327-4a43-9b90-d7d7369139a1@e53g2000hsa.googlegroups.com... > > My question came up when a friend of mine asked if I could change out > > his Federal Pacific breaker box to a newer, safer one. My background > > is in industrial controls and I don't normally deal with power at the > > service level. I only have about two years experience so as I am now > > trying to learn more on my own, I'm finding a lot of things that don't > > add up. > > > Dude, don't go there. Have you ever heard of anyone changing out their own > breaker panel, much less doing it live? No? Huh, wonder why that is? > > The power that'll slam into you through 0 or 2 ga wire is HUGE and > UNFUSED... thousands of amps. The transformer on the pole has overload > protection, but it won't kick in until WAY after you're dead. > > What you are considering is RIDICULOUSLY DANGEROUS. Trained professionals > don't do it. I had to do one live in the '70s. The utility company said they wouldn't reinstall the meter for at least three working days after they were notified that the work was done, unless I used their 'authorized electrician' who wanted about $1200 to install the new box I had. That would have been at least 24 hours. I pulled the main fuse cartridge, and removed the tops of the old fashioned clamshell clamps, then wrapped each wire in electrical tape, followed by friction tape. I didn't want to do it hot, but it was the middle of August, and the fuse box was _very_ overloaded. We would have lost a freezer and refrigerator full of food if I let the 'authorized electrician' do the work. There was no way I was going to pay $1200, and lose over $300 worth of food for an hour's work. I had someone right there with an insulated rod, in case something went wrong. I removed the neutral and ground connections first, and connected them last in the new box. That way if I slipped and either side of the line touched the box, it wouldn't arc. I agree that it shouldn't be done, but then I have worked on the HV power supplies on TV transmitters, reconnected pole mounted CATV power supplies to the secondaries (240 VAC lines run between power poles) after a repair, and other dangerous things because it was part of my job. All it takes is one careless move, and you die. -- http://improve-usenet.org/index.html Use any search engine other than Google till they stop polluting USENET with porn and junk commercial SPAM If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm |
| 09 May 2008 19:09:36 |
| Dave |
| Re: Changing Breaker Box - Looking for Different Perspective |
"Michael A. Terrell" <mike.terrell@earthlink.net > wrote in message news:TIednQoOGrhwC7nVnZ2dnUVZ_tninZ2d@earthlink.com... > There was no way I was going to > pay $1200, and lose over $300 worth of food for an hour's work. > Would your wife and kids agree that $1,500 is WAY more than your life is worth? Or not... Life is full of unavoidable risks, why tempt fate when the odds are against you? I doubt the OP was even cognizant of the risk factor prior to his post, he is the WRONG person to attempt this... it would be beyond "dangerous", it would be reckless and stupid. > > All it takes is one careless move, and you die. > Edzackery. > -- > http://improve-usenet.org/index.html > > > Use any search engine other than Google till they stop polluting USENET > with porn and junk commercial SPAM > > If you have broadband, your ISP may have a NNTP news server included in > your account: http://www.usenettools.net/ISP.htm |
| 09 May 2008 16:37:32 |
| Michael A. Terrell |
| Re: Changing Breaker Box - Looking for Different Perspective |
Dave wrote: > > "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in message > news:TIednQoOGrhwC7nVnZ2dnUVZ_tninZ2d@earthlink.com... > > > There was no way I was going to > > pay $1200, and lose over $300 worth of food for an hour's work. > > > > Would your wife and kids agree that $1,500 is WAY more than your life is > worth? Or not... I wasn't married, and I didn't have the $1500. I also did industrial electrical work. > Life is full of unavoidable risks, why tempt fate when the odds are against > you? I doubt the OP was even cognizant of the risk factor prior to his > post, he is the WRONG person to attempt this... it would be beyond > "dangerous", it would be reckless and stupid. > > > > > All it takes is one careless move, and you die. > > > > Edzackery. I also replaced the service entrance cable on a friend's house. The insulation was so bad that you could see the two line conductors inside the spiraled neutral. A fiberglass ladder, a hacksaw, and I worked on one conductor at a time. After hacksawing them off from the drop, they were taped up. Then the old cable & meter socket were removed. The cable to the breaker box was replaced, the new meter box was mounted, then the new service cable was spliced to the drop with new split bolts and No-ox, then properly insulated. The city inspected it an hour later, passed it, and resealed the meter. -- http://improve-usenet.org/index.html Use any search engine other than Google till they stop polluting USENET with porn and junk commercial SPAM If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm |
| 12 May 2008 09:38:23 |
| emilio_estevez |
| Re: Changing Breaker Box - Looking for Different Perspective |
Well, I've already gotten a hold of the Electic Company to come out and pull the meter. And there have been several things brought up that could go wrong that I didn't think of. But... the answer to my main question hasn't been answered. I have decided that it is not worth doing it live because of several of the possible accidents mentioned above. I realize that, because there is basically no circuit protection, an accidental short could create thousands of amps resulting in an enormous arc flash. But, what I still don't understand is when Dave said that, "The power that'll slam into you through 0 or 2 ga wire is HUGE". I know that size of wire is capable of delivering extremely high currents -- but that's what it's capable of doing. Not what it would actually do. If someone gets shocked by the 120V at an outlet or switch in their home, that wire is capable of delivering 20 amps before the breaker trips. But if you get shocked by it, the breaker doesn't trip because the resistance of your body keeps the current low. If you're body doesn't even trip out a 15A breaker, I don't see how the fact that because you use bigger wire, the current that flows with 120V potential, through your body (high resistance), to ground is any different. Sure there's plenty of reasons not to change a breaker box hot, but i still don't see how any of them have to do with the fact that getting shocked by the incoming feed is any deadlier than the 120V anywhere else. I really believe that it's just a misconception, and that the only true danger is the possibility of an arc flash because of an accidental short. |
| 12 May 2008 15:48:06 |
| Michael A. Terrell |
| Re: Changing Breaker Box - Looking for Different Perspective |
emilio_estevez wrote: > > Well, I've already gotten a hold of the Electic Company to come out > and pull the meter. And there have been several things brought up > that could go wrong that I didn't think of. But... the answer to my > main question hasn't been answered. I have decided that it is not > worth doing it live because of several of the possible accidents > mentioned above. I realize that, because there is basically no > circuit protection, an accidental short could create thousands of amps > resulting in an enormous arc flash. > > But, what I still don't understand is when Dave said that, "The power > that'll slam into you through 0 or 2 ga wire is HUGE". I know that > size of wire is capable of delivering extremely high currents -- but > that's what it's capable of doing. Not what it would actually do. If > someone gets shocked by the 120V at an outlet or switch in their home, > that wire is capable of delivering 20 amps before the breaker trips. > But if you get shocked by it, the breaker doesn't trip because the > resistance of your body keeps the current low. If you're body doesn't > even trip out a 15A breaker, I don't see how the fact that because you > use bigger wire, the current that flows with 120V potential, through > your body (high resistance), to ground is any different. > > Sure there's plenty of reasons not to change a breaker box hot, but i > still don't see how any of them have to do with the fact that getting > shocked by the incoming feed is any deadlier than the 120V anywhere > else. I really believe that it's just a misconception, and that the > only true danger is the possibility of an arc flash because of an > accidental short. He means there is less resistance to limit the current, so any accident can be _much_ worse. A single strand of fine wire can vaporize and create plasma that will continue to arc, because you have a much higher fault current available. -- http://improve-usenet.org/index.html Use any search engine other than Google till they stop polluting USENET with porn and junk commercial SPAM If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm |
| 14 May 2008 11:21:41 |
| bud-- |
| Re: Changing Breaker Box - Looking for Different Perspective |
emilio_estevez wrote: > > Sure there's plenty of reasons not to change a breaker box hot, but i > still don't see how any of them have to do with the fact that getting > shocked by the incoming feed is any deadlier than the 120V anywhere > else. I really believe that it's just a misconception, and that the > only true danger is the possibility of an arc flash because of an > accidental short. An additional hazard is in most panels there is a lot of exposed metal that is hot. It is real easy to make accidental contact. And easy to make contact with larger skin area which means lower resistance. You can also get across 240V. -- bud-- |
| 14 May 2008 21:42:41 |
| Rich Grise |
| Re: Changing Breaker Box - Looking for Different Perspective |
On Mon, 12 May 2008 09:38:23 -0700, emilio_estevez wrote: ... > Sure there's plenty of reasons not to change a breaker box hot, but i > still don't see how any of them have to do with the fact that getting > shocked by the incoming feed is any deadlier than the 120V anywhere > else. I really believe that it's just a misconception, and that the > only true danger is the possibility of an arc flash because of an > accidental short. It's not about getting electrocuted - it's about the explosion of copper vapor that happens when you feel the tickle, react, and short one of the hots to ground. =:-O Be Safe! :-) Rich |
| 15 May 2008 18:55:41 |
| sparky |
| Re: Changing Breaker Box - Looking for Different Perspective |
On May 14, 5:42=A0pm, Rich Grise <r...@example.net > wrote: > On Mon, 12 May 2008 09:38:23 -0700, emilio_estevez wrote: > > ... > > > Sure there's plenty of reasons not to change a breaker box hot, but i > > still don't see how any of them have to do with the fact that getting > > shocked by the incoming feed is any deadlier than the 120V anywhere > > else. =A0I really believe that it's just a misconception, and that the > > only true danger is the possibility of an arc flash because of an > > accidental short. > > It's not about getting electrocuted - it's about the explosion of > copper vapor that happens when you feel the tickle, react, and > short one of the hots to ground. =3D:-O > > Be Safe! :-) > Rich About 30 years ago I was employed by a mining company for maintaining electric hoisting motors. One of the motors was an 8000 Hp DC motor operating from an SCR bank at 1000 VDC. The armature breaker was installed in a room about 10 feet square. The door was interlocked so the motor could not be energised if the door was open. One day the breaker failed. The entire room looked like it had been painted with copper. The breaker contacts had vaporized and the copper condensed on the walls of the room. Thank God for interlocks! |