# For those wanting to add 220 svc or expand existing svc in shop



## woodbutcherbynight (Oct 21, 2011)

Yesterday my neighbor calls me in a panic to tell me how his breaker box caught on fire and wanted me to come up and see about getting a new one installed. As you can see from the picture the box got HOT, Chernobyl hot people! Those that work with electricity can tell immediately what was wrong, for those that do not allow me to explain what went wrong and how it applies to expansion of our own shop electrical.

They had replaced the HVAC service breaker at the compressor with a 30 amp breaker because the old one did not work. Inside the main breaker box this breaker was fed power from another 30 amp breaker. The unit was marked for a maximum of 20 amp breaker. In such cases more is NOT better. The problem was with the compressor, it has died and when engaged draws high amps trying to work. By using a 30 amp breaker verses 20 amp the wires of the circuit now carry more amps than needed creating HEAT. Bypassing the breaker and forcing the unit to work created a lot of heat from the high amp draw of a bad compressor. Left unchecked the box continued to heat up until melting point, then the fire starts. Fortunately the homeowner was able to respond quickly and put fire out, then kill the power. Four hours of work and we had rewired the new panel and had power minus a/c.

Lesson to be learned. Sure just upping the breaker to higher amps gives you what you need for power but the wiring to that breaker has limits. If and when a tool or device shorts the breaker with correct wire will support the brief overload and shut down. But when you ignore this and have smaller wire and higher amp breaker you create heat, and electrical fire can and often does result. The device need not be drawing excessive amps to create a problem. The combination of excessive draw on smaller wire with higher than rated breaker is a disaster in the making.

While I am not a pro in this regard I do know the basics and by ignoring them we invite disaster. Sure it costs money to have a pro come and do it correctly but the risk here is at minimum your shop and house, or worse you. Having the circuit wired according to code, with the correct breaker for the appropriate load is for a reason, not merely a suggestion. My neighbor got lucky this time and has learned a valuable lesson that cost him $300 and about six hours of time repairing and cleaning up. Not to mention his wife's reaction and subsequent rant on being an idiot. (I left as this got too heated for me.)

For those more knowledgeable on this please add more warnings or better explanations. I know it is sometimes about cost but let's be safe, cutting corners is not a good practice.


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## hoss12992 (Mar 20, 2013)

Very Well explained. I gotta admit I was laughing at the part where the neighbors wife started fussing at him. One thing I learned in my youth and have preached to my kids is safety first and cheap ain't always cheap.


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## woodbutcherbynight (Oct 21, 2011)

Yeah she was not too happy about the burnt smell and it was rather strong. Finished about 2330 last night after a full day at work I was beat. Did not get any finish work done on my own projects which are many!!!!! LOL


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## Holbs (Nov 4, 2012)

When I wired my garage, it took 3 months of research about electrical installs. Lots of OSHA pics of wrong doings, inspector's summary of what they did wrong, lots of how things are to be done right, do's and dont's. I did everything by code to play it safe, even if it's overkill. Because I can only assume most of the entries into electrical code are done for a reason towards safety and experience of bad doing's


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## BillWhite (Jul 23, 2007)

Wise words for sure.
There are those thing that I know, and there are things that I don't know.
Wisdom come from being able to differentiate.
Great post.
Bill


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## Mike_D_S (May 3, 2012)

Always good to be reminded that things can happen. Just to make sure I'm clear, the root cause is that they put 30 amp breakers on both sides of a wiring run with wire gauge only appropriate for 20 amp service?


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## woodbutcherbynight (Oct 21, 2011)

> Always good to be reminded that things can happen. Just to make sure I m clear, the root cause is that they put 30 amp breakers on both sides of a wiring run with wire gauge only appropriate for 20 amp service?
> 
> - MikeDS


That is correct, this was an accident waiting to happen. So when the compressor died the high amps went straight to the breaker box and overheated the main bus, then FIRE. Had the correct breaker been in place it would have shut down before the wiring overheated. They replaced the a/c this afternoon and upon inspection the compressor had gotten so hot it had no paint and the metal decal plate was no longer readable.

Another neighbor commented the house was just old and these things happen. Perhaps but then he cannot see out of his right eye and has bad burns on his face and arms. Seems he tried to jump his car off one morning with a extension cord run to an house outlet. 120 AC cannot be used to "jump" a 12 DC battery….EVER!!!


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## Mike_D_S (May 3, 2012)

> Another neighbor commented the house was just old and these things happen. Perhaps but then he cannot see out of his right eye and has bad burns on his face and arms. Seems he tried to jump his car off one morning with a extension cord run to an house outlet. 120 AC cannot be used to "jump" a 12 DC battery….EVER!!!
> - woodbutcherbynight


The electron thingy makes the spinny thingy go roundy round?

While you never want to see anyone get hurt, it does make me wish there was video…..


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## woodbutcherbynight (Oct 21, 2011)

> While you never want to see anyone get hurt, it does make me wish there was video…..
> 
> - MikeDS


Indeed but then I would have to go to hospital for the pain caused from laughing that hard. I hear about this stuff sometimes and just shake my head.


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## JeffP (Aug 4, 2014)

So the compressor failure somehow produced a situation where the compressor was using more than 20 amps but less than the 30 that would have kicked the wrongly sized 30 amp breakers?

That's kinda weird.


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## becikeja (Sep 12, 2010)

> The electron thingy makes the spinny thingy go roundy round?
> 
> While you never want to see anyone get hurt, it does make me wish there was video…..
> 
> - MikeDS


This video is a 480V panel, so not exactly the same, but what happened is very similar.
The wire burns and goes to ground casing an arc flash event.

Watch the video. Then respect the power.


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## TheFridge (May 1, 2014)

Looks like branch circuit wiring shorted the mains out. Awesome.


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## JBrow (Nov 18, 2015)

woodbutcherbynight,

I trust your neighbor replaced the cable from the load center to the a/c before powering up the new unit. I would be surprised if the cable servicing that circuit emerged unscathed from the overload.

Some time ago there must have been a sale on those 30 amp breakers. When I purchased our current home I noticed about half a dozen 30 breakers protecting 120 v circuits, most of which were household lighting circuits. On closer inspection I noted that 14 gauge wires fed those circuits. Fearing an accident like that you described, I immediately replaced the 30 amp breakers with 15 amp breakers. It made me wonder what the prior homeowners were thinking; I can only guess they were oblivious to the danger.


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## woodbutcherbynight (Oct 21, 2011)

*JBrow*

Yes the wiring from main breaker box to service box and from service box to new A?C unit was replaced including a new service panel. A electrician friend of ours came out and checked the work and gave a few tips on some things to get right before ever trying to sell the house. So with the exception of the a/c power circuit and breaker box my neighbor got off cheap. He does now have a healthy respect for screwing with electricity.

The old breaker box happens to be the right size for a drawer I want to make for under a cabinet. With some paint work it will look good as new. LOL.


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## tealetm (Jan 20, 2016)

So why did the wire become hot just at the breaker location? Wouldn't/couldn't it have failed or burned at any point between the breaker and the load?


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## nightguy (Aug 2, 2016)

> So why did the wire become hot just at the breaker location? Wouldn t/couldn t it have failed or burned at any point between the breaker and the load?
> 
> - tealetm


I have limited knowledge of electricity, I only made the stuff for 20 years, yes it could have, I am guessing in the breaker box was a situation of more resistance, and that is why the heat build up there, and not in the wire run.


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## TopamaxSurvivor (May 2, 2008)

> So why did the wire become hot just at the breaker location? Wouldn t/couldn t it have failed or burned at any point between the breaker and the load?
> 
> - tealetm


Electrical failures occur at connection points that become loose or are poorly made to start with by error or just plain incompetence on the part of the installer or are a failure of poor, cheap manufacturing processes.

That is a cheaply made panel. I saw a lot of similar issues in them on service calls. The connection where the breaker connects to the buss bar failed. The breaker failed to trip. The main failed to trip when short circuit that burn up the panel started. The list of failures goes on and on. ;-( The main is not a 200 amp breaker. It is 2 - 100 amp breakers in parallel. Perfect example of why I only installed Square D and Cutler Hammer products. If the customer wanted another brand, I told them to call some one else.


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## JeffP (Aug 4, 2014)

> The connection where the breaker connects to the buss bar failed. The breaker failed to trip. The main failed to trip when short circuit that burn up the panel started.
> - TopamaxSurvivor


...so, not trying to put words in your mouth, just trying to see if I understand your point…are you saying the OP's assessment of what caused the fire (replacing 20 amp breakers with 30) was incorrect? Are you saying it looks to you like some of the breakers in this box (possibly including the mains breakers) did not do their job? And poor breaker connections then caused heat and fire when a very high over-current occurred?

If so, then my "gut" agrees with you. I speak not from experience, but just from logic. This explanation makes sense to me, whereas the 30 vs 20 did not. Not suggesting that replacing breakers with higher values is a good idea…just didn't make sense (to me) as an explanation for this breaker-box fire.


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## Mike_D_S (May 3, 2012)

> ...so, not trying to put words in your mouth, just trying to see if I understand your point…are you saying the OP s assessment of what caused the fire (replacing 20 amp breakers with 30) was incorrect? Are you saying it looks to you like some of the breakers in this box (possibly including the mains breakers) did not do their job? And poor breaker connections then caused heat and fire when a very high over-current occurred?
> - JeffP


Jeff,

Let me explain it in a different way. Say you have a wiring run that is 14 gauge romex (not romeo, stupid spell check) o rated for 17 amps. That rating is based on a certain max temp of the wire, etc. The big factor is how well the wire can dissipate the heat buildup that occurs in any wire when the current passes through it. The more current you pass through that small wire, the more heat is has to dissipate.

So take that wire rated to 17 amps and run 25 amps through for a while. It's going to get hot and it's going to get hot fairly evenly over it's length. But the difference is in the materials outside the wire. The wire is finally going to fail is the place where the heat can build up the most. If you think about an electrical box as an enclosed metal space with a bunch of heating elements in it (wiring under load) then maybe it's not so crazy that the failure was in the box.

A failure doesn't necessarily require a large over current situation, loading a wire rated for 17 amps at close to 30 amps could do it as well if the wire can't dissipate the heat.

There are also ways a motor can be failing and draw extra current that might trip a 20 amp breaker but not a 30 amp. Say if one of the bearings was failing, that extra load would raise the amp draw on the motor, but not be an actual short.

Not saying this is the cause for sure, but the OPs assessment might be exactly right. If they had a 20 amp breaker on there matched to the capacity of the branch wiring, that could have potentially prevented the issue.

Of course it could be a ton of other things like a loose wire connection at the breaker, corroded or damaged bus bar contact, etc. Anything that increases the resistance and creates heat could have done it.

Mike


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## Lazyman (Aug 8, 2014)

Yup, breakers are there to protect the wiring, not the devices plugged into it. Devices that need to have their wiring protected will have their own breaker built in to them. While a breaker could have been faulty and needed to be replaced (with the same amp breaker), a breaker that trips almost always means that the device at the end is faulty in some way or you have in some other way overloaded the wires on that circuit. You second guess the breaker (and the qualified electrician who installed it) at your own peril.


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## TopamaxSurvivor (May 2, 2008)

JeffP, It is a poor connection of the breakers to the buss bar that caused the heat. It can happen with a proper load over time in those panels. That much heat should have tripped the breaker and the main if they were working properly. Any breaker that is designed to be installed in that panel should not do that regardless of the load. I have seen overloads of 30 or 40 amps trip the main in a Sq D or CH panel simultaneously with the small branch circuit breaker. I have never seen one of those panels fail as in the incident cited above.

In 45 years, I saw a lot of electrical failures, but never wire failing in the middle of a run. Always at a connection point unless it melted the insulation inside a conduit causing a short circuit to ground. I suppose it is possible, but I never saw it doing mostly commercial and industrial work. Insulation on wire is thermosetting. It stays put unless there are mechanical forces causing pressure to push the conductor out against an object.

I know of one instance where a fellow had 60 amps of lights on a 20 amp circuit for 2 or 3 hours. The insulation in the conduit melted causing a short. That finally tripped the breaker. A square D or Cutler Hammer breaker with both thermal and magnetic actuation would have tripped instantly. It is nearly impossible to strike a visible arc with a wire protected by those 2 brands.

I keep seeing on here that circuit breakers are to protect wiring only. The National Electrical Code says their purpose is to protect everything including utilization equipment. I wonder where and how these rumors and ideas get started? The majority of utilization equipment plugged into general purpose outlets do not have any kind of short circuit or overload protection. Overload protection in motors is not short circuit protection. Those 2 types of protection are different. Both are required to properly protect motorized equipment against failure and fire hazard.


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## pete724 (Mar 9, 2016)

> So why did the wire become hot just at the breaker location? Wouldn t/couldn t it have failed or burned at any point between the breaker and the load?
> 
> - tealetm


The wire probably DID become hot.
And probably hottest at the connection point between the breaker(in the box) and the wire.
Whoever put that breaker in and connected a 20AMP circuit(wire) to it , certainly was NOT a good electrician.
Whoever that installer was probably didn't have the breaker set into the box properly either.
And they probably used some cheap/off brand breaker.

So things almost certainly happened the way TopamaxSurvivor said.

After the initial heat.


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## TheFridge (May 1, 2014)

theyre all guesses at this point.

I doubt the bussing burnt because of the breaker. That looks more like the insulation failed on the first and shorted to many of the others and probably the main as well.

It's rare to see a breaker that doesn't burn itself out and lose connection with the bus. That's catastrophic failure there.

Square D is good but when there's a line to line short on a 30A circuit and it throws a 400A main it's huge effing pain.


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## Lazyman (Aug 8, 2014)

> I keep seeing on here that circuit breakers are to protect wiring only. The National Electrical Code says their purpose is to protect everything including utilization equipment. I wonder where and how these rumors and ideas get started? The majority of utilization equipment plugged into general purpose outlets do not have any kind of short circuit or overload protection. Overload protection in motors is not short circuit protection. Those 2 types of protection are different. Both are required to properly protect motorized equipment against failure and fire hazard.
> 
> - TopamaxSurvivor


To clarify what I meant by "protect the wiring": I am not an electrician but my understanding is that the breaker is sized to protect the wiring from overheating and causing a fire when 1 or multiple devices on the circuit combine to exceed the rating for the wiring of the circuit (based upon gauge and length). A 30 amp breaker may not protect a 15 amp motor for example from overloading its own wiring, thereby destroying the motor and possibly even starting a fire. As long as the motor does not exceed the 30 amp limit while it is melting down, it might not trip the breaker. This is at least one reason that table saws usually have a breaker built in that is designed to trip if it exceed its maximum rating for more than a couple of seconds. I am not sure how exactly a breaker provides short circuit protection. My assumption has always been that they rely on the fact that a short circuit often results in high current that exceeds the trip rating of the breaker but perhaps that is not the case.


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## ArtMann (Mar 1, 2016)

I am an electrical engineer and volunteer electrician for a couple of benevolence organizations. I have read the 2012 version of the NEC extensively and have never seen any reference to a breaker protecting the device plugged into it. If there is such a reference, please post the NEC version, Section, subsection and paragraph. I wrote an analysis of this issue for another forum. Here it is.

The question of breaker protection of either equipment or life comes up on the forum fairly often. I would like to offer a long winded explanation of why I think a breaker is very unlikely to do either of those things. It can't be explained in just a few sentences.

First of all, we need to understand the behavior of residential and commercial breakers. A breaker will not open at the instant the current goes above the rated current. They are designed this way in part to compensate for very high startup currents of some electrical devices. For example, a 20A rated compressor motor, which is already under a mechanical load, might draw 60A as it is coming up to speed. The behavior of a breaker is defined by the "trip curve" for the device. It gives you the trip time as a function of the percent current overload. You can easily obtain this curve for each brand and family of breakers on line from the manufacturer. As an example, a typical 20A breaker will sustain 40A for about a minute and 200A for a few seconds.

What does this say about the ability of a breaker to protect a human from electrocution? The average lethal current is estimated to be something like 0.01A or 0.03A. A 20A breaker will sustain 2000 times that amount of current indefinitely. Fortunately, a person will typically pull away more quickly than the time it takes to stop the heart. In this situation, a breaker will do nothing to protect a person if he touches a chassis, housing or enclosure of a machine that is shorted to 120 or 240 VAC. Of course the breaker will trip right away if the chassis, housing or enclosure is grounded. Proper grounding of all equipment is the real protection.

What about protection of machinery? Well, there are several different ways a piece of equipment may be destroyed electrically and each must be considered separately. The most likely scenario is stalling of a table saw or other cutting machine. In this case the current will rise to what is called the "locked rotor" current. This current is large but it is limited by the resistance in the windings. You might get 5 or 6 times the design current of the motor. A typical breaker might sustain this level of current for 5 or 10 seconds - long enough to burn the relatively small wire in the windings. Fortunately, almost all modern machinery has internal thermal overload protection.

Another possibility is that the wiring external to the motor has been damaged in some way to create a partial or complete short. In this case, the breaker may open up in due time and let you know you already have a problem but you might notice smoke first. It won't prevent you from having the problem.

Yet another possibility is that something goes wrong inside the motor housing. If it is a dead short, then the breaker will trip but, as above, the damage has already been done. It will only inform you that you already have a problem that needs repair. If there is a partial short so that the current is limited, then you might sustain further damage before the varnish on the winding melts to cause a dead short. Unfortunately, this limited current will delay the breaker substantially. Remember that a breaker will sustain twice the rated current for a minute or more. That is fast enough to protect the service wiring but not enough to prevent further damage in the motor. Disassemble an old motor some time and compare the diameter to the diameter of the house wiring.


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## TopamaxSurvivor (May 2, 2008)

> theyre all guesses at this point.
> 
> I doubt the bussing burnt because of the breaker. That looks more like the insulation failed on the first and shorted to many of the others and probably the main as well.
> 
> ...


With all due respect, I have seen this a lot especially in Zinsco and ITE panels.

What I meant to say about Square D and C&H is a 30 or 40 amp short will trip a 200 amp main sometimes. Breakers are normally coordinated to trip in order. It is better to have a little PIA to deal with rather than catastrophic failure.


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## TopamaxSurvivor (May 2, 2008)

> Whoever that installer was probably didn t have the breaker set into the box properly either.
> And they probably used some cheap/off brand breaker.
> 
> So things almost certainly happened the way TopamaxSurvivor said.
> ...


Not much the electrician can do in that case about installing the breaker properly other than know better than to use the cheap garbage panels. When adding to an existing installation, I always advised the owner of the risks and to expect problems in the future.


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## TopamaxSurvivor (May 2, 2008)

*ArtMann* Good attempt to put it in layman's terms. Not an easy task. Many electricians do not understand the difference between overload and over current protection. I spent most of my career as a go to guy resolving the unresolvable. Most of the motors I have found burned out were not properly protected and most never are unless the device is integral from the manufacturer.

Not sure if that is a typo or if you are looking at a different code. There is no 2012 NEC. 2011, then 2014. It is a 3 year cycle. I retired 2.5 years ago and can't find my code 2011 book right now. Circuit breakers protecting more than just the conductors is in the definitions in Article 240, I believe. You can't goggle to get the text. NFPA protects their copyright and sells the code books for long Yankee green. There are other places in the code that specify breaker sizing to protect various types of equipment. Article 430 is a good example about motors. The circuit breaker sizes on many types of equipment are required to be specified by the manufacturer's label. There are several other standards by UL and others that have to used in conjunction with the NEC. Everytime you look something up in the NEC, there is an exception, contradiction or "gottcha" somewhere for many circumstances.


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## Mike_D_S (May 3, 2012)

@Topamax,

FYI, the NEC will let you view the code books online for free via their website. Though finding the actual link can be tricky.

Mike


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## jimintx (Jan 23, 2014)

There is at least a good chance that I understand basic home wiring and circuitry. I have worked with it for a few decades, or so. I do not think the explanation that started this thread makes sense.

HOWEVER, the real key here to me is to do electrical stuff "Right".

Don't make assumptions of what might work, and don't guess. Don't use a brute force method to bypass breaker protection via hardwiring or via "just using a larger breaker".

If you don't have a solid understanding of what "Right" is, then you have to get someone to help you that really does know what to do and how to do it. 
,


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## ArtMann (Mar 1, 2016)

The copy of the NEC I have was downloaded from the NFPA website and was released because it is obsolete (although many municipalities and County authorities still reference it). It must have been the 2011 edition.

Edit: I just checked and it is indeed the 2011 edition I have as a pdf file.


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## woodbutcherbynight (Oct 21, 2011)

> There is at least a good chance that I understand basic home wiring and circuitry. I have worked with it for a few decades, or so. I do not think the explanation that started this thread makes sense.
> 
> HOWEVER, the real key here to me is to do electrical stuff "Right".
> 
> ...


My neighbor had the insurance adjuster send out an electrician and a HVAC guy. This is what they have explained with the neighbor admitting more of what he and his friend actually did. Hopefully this clears up some details, it has become a neighborhood soap opera as it has been repaired.

1. A/C quit working, they found the 30 amp breaker at the svc panel outside burnt.
2. They installed a new 30 amp breaker and it tripped. Decided it was bad and BYPASSED it with hard wire.
3.A/C Fan came on and thinking it was working again they started to pack up.
4.The kids came out of the house screaming it was one fire, at this point they heard popping from breaker panel inside.
5.FIRE see pics. LOL
6.The wires from the svc panel to the main breaker panel are melted together in one blob of goo.
7.Main feed from meter to breaker panel got scorched and has to be replaced
8.The happy go lucky wiring job they did adding a 60 amp service box to a building in backyard melted badly
9.HVAC found the motor in the A/C unit was bad, so new a/c unit is coming another $5000
10.Drier is toast, did not even ask what happened I was already laughing to hard.
11.How my neighbor survived "putting out the fire" by pouring beer on it without electrocuting himself is beyond me.
12.Discussion is still ongoing on how many wires will be replaced that look melted from fire.


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## TopamaxSurvivor (May 2, 2008)

Thanks Mike, I was never tricky enough to find it.

woodbutcherbynight, interesting little adventure they had ;-) I have been in on a few fired investigations and repairs. Some of the work I saw I would consider attempted arson rather than a code violation. One of the worst was 14-2 romex being used to feed a 60 amp sub-panel in a school. The bare ground conductor was used for the neutral and there was no equipment ground.

I saw copper tubing replacing fuses in a machine shop panel. They didn't blow when the the new welder came on.

One guy reset the breaker that a 3 phase 480 motor was blowing about 3 or 4 times within about 10 minutes. Last time he reset it, it blew immediately and blew the door on the motor control center bucket open. That took a little piece off of his ear when it swung open. He decided it as time to call for professional help ;-)


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