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Unfused connectors MELTED House wires WHAT TO DO???

21K views 63 replies 18 participants last post by  Scuba_Dave 
#1 ·
HI;

**I could really use some help from the experianced folks on this one, as the liceansed electrician was just lost in terms of knowing what wires are safe** Thanks in advance.

This is a true story about what happened to my dad and his house last night when working in his panel. This shows just how dangerous working around unfused service conductors is, even with your panel off. My dad is very lucky that there was no arc flash of any size. No one was injured, luckly, but it could have easily been a very different story.

My dad was trying to trace some circuits in his panel, with the main pulled. I don't know exactly how it happened, I wasn't in the basement at the time. Thank god he was using one of my klien insulated tools. He someone had a #4 awg bare wire that was connected to the water meter contact a unfused service conductor. This energized every metal part in the house. It melted through the clamp on the water meter cutting a hole in the pipe, flooding the basement.

I suspect that the circuits on other leg of the panel, not the one he made contact with became energized with 240V +/- any resistance from items on these lines.

As soon as I realized he had energized everything metal in the house, and wires were smoking and melting, I demanded he get away from the house and I would not even let him pull the meter because everything was energized. Calls to 911 and to the power co for an emergency dc at the pole were made.

It took the power co almost an house to dc at the pole and remove the meter. The entire time wires were melting and smoking. A number of the romex wires in the basement had the insulation melt and drip off the wires.

After the power co came and the fire dept cleared the house as safe, and the water got shut off at the streetWith power off at the pole ; I tested contunity between the neutral and hots. 4 or 5 of the circuits had continuity.

A liceansed electrican was called and came out. He grounded the system, to a old rod (one that was never connected to the electrical system) and rebonded to what was left of the water pipe. He did not replace the SE cable or anything else. He then had the power co restore power. I have all the breakers off, except for 2, where I put new wire in for the furnace and a utitilty outlet at the panel.

I asked the electrician, about how we can know if any of the wires in the house are safe or useable. I asked him about meggering he knew what it was but didn't have access to the equiptment to do it.

I know much is going to have to be rewired. This is a house from around 1917, very hard to fish wire in.

My question here is, If some of the branch circuits appear to look good physically, and I test the continuity on the wires with a sensetive meter, would that tell us the wire is safe to use? My concern is that the insulation may still be partially melted through, and there is a arcing hazard later on when there is a load on the branch circuit. Would Meggering actually tell us if they were safe to use?

The liceansed electrican just didn't know, and he was going to just turn on all of the branch ciruits that were not dead shorting. I was not comfortable with that at all, and I turn off everything, but the 2 circuits I did with fresh wire.

Do you think there is any chance of using any of the old wire safely? Do you think that the wires that were on the leg of the panel that got grounded out would be more likely to be ok, since they were not fed 240?

What would you guys do in this situation. It is a large 3,000sqft old house, very difficult to fish wires in. I bet this is going to be 10,000-20,000$ if the whole house needs a rewire due to the complexity of the wire fishing.

Any thoughts are greatly appriciated.

AGAIN FOR THE RECORD, AS I KEEP TELLING PEOPLE; UNFUSED SERVICE CONDUCTORS ARE VERY DANGEROUS, STAY AWAY FROM THEM IF YOU DON'T FULLY UNDERSTAND WHAT YOUR DOING!!!

Thanks guys,

Jamie
 
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#3 · (Edited)
Only the wires with crispy insulation carried heavy current. If the current was that heavy, smaller wires that carried heavy current would already read as an open circuit.

I think that during the short, the voltage applied to the rest of your house was less than 1v.

The fusing current, and power, for a copper pipe containing water must be enormous. Maybe people on a physics website could calculate this. I think your panel can deliver 240kA so it would be some current less than this value.
#6 copper melts at 700A.

I would imagine that insulation heated this hot would read higher megohms than normal.
 
#5 · (Edited)
What you had was a short circuit from the unfused terminal in the panel down the #4 wire to the clamp and pipe. From the latter location some current will go to ground where the pipe exits the house but if there is another path, back to the panel ground, current will also take that.

Are (ground) wires clamped to pipes anywhere else in the house? If so, those circuits would need more investigation in case large short circuit current used the plumbing system and then used their ground wires to get back to the panel.

Are the melted wires just at the panel (physical as opposed to electrical heat damage) or does the damage extend several feet?

Meanwhile simply making the neutral or ground wires hot with 240 volts because a hot wire touched the panel grounding bar it is not going to fry the branch circuits. There must be a flow of current from one place to another for example the wire in question was grounded in one place and energized in another place.

The pipe got melted at the pipe clamp because there was not all that good a connection where the #4 wire was clamped on. Good enough for maybe 20 amps of current from a short from a breaker protected branch circuit but not for what may have been 1000 amps (limited only by the pole transformer fuse) from the unfused contact in your panel.

When testing for continuity to prove the existence of a short in a branch circuit, don't forget to unplug everything from that circuit. An incandescent light bulb will test only a few ohms since the resistance of the filament is very small when the filament is not hot.
 
#6 ·
What you had was a short circuit from the unfused terminal in the panel down the #4 wire to the clamp and pipe. From the latter location some current will go to ground but if there is another path back to the panel current will also take that.

Are (ground) wires clamped to pipes anywhere else in the house? If so, those circuits would need more investigation in case current used their ground wires to get back to the panel.

Are the melted wires just at the panel or does the damage extend several feet?

Meanwhile simply making the neutral or ground wires hot with 240 volts because a hot wire touched the panel grounding bar it is not going to fry the branch circuits.

The pipe got melted at the pipe clamp because there was not all that good a connection where the #4 wire was clamped on. Good enough for maybe 20 amps of current from a short from a breaker protected branch circuit but not for what may have been 1000 amps (limited only by the pole transformer fuse) from the unfused contact in your panel.

It would take breaking/falling of (primary) wires up on the utility poles and carrying several thousand volts and their unwanted contact with the 120/240 volt (secondary) wires serving homes before entire home electrical systems would get fried.

When testing for continuity to prove the existence of a short in a branch circuit, don't forget to unplug everything from that circuit. An incandescent light bulb will test only a few ohms since the resistance of the filament is very small when the filament is not hot.

Finally, if you just flipped on the breakers of the seemingly undamaged circuits (after repairing the panel), the worst that would happen is that a 15 amp or 20 amp breaker would trip again if there was a short in that circuit.
I was concerned that something could arc and start a fire without opening a breaker, I thought that might be even a greater concern with the knob and tube. Since the house wiring is old most is not grounded. So if it was shorting to say a metal box due to melted insulation, then the breaker would not open if that box is not grounded. Thats my concern.

There is atleast 15-20 feet of nm/ romex going across the room that is just melted, it had no direct contact with the fault in the panel, other than being connected to the neutral bar.

I am going to pull some more suff apart this afternoon and physically how far from the panel stuff has melted.


If I connect the hot and neutral on a circuit at the far end, and test from the panel, I should see a very very small ohm reading, even with a somewhat long run, correct? Would I just estimate the distance of the run and multiply it by 0.000078 per foot? and see if I get close to that reading on a ohm meter? How accurate of a test would that be?

I may have to buy a Fluke 1587 or similar.

Thanks
Jamie
 
#7 ·
The only way I know of to judge the integrity of any cable is to megger it.

This test applies a high DC voltage (for house wiring, I'd use 1000 volts), and measures the current on the return. A couple of milliamps would be acceptable. The idea here is that if a circuit can stand 1000 volts and not leak more than a few milliamps, it'll stand 120 volts with much less leakage. Usually, we megger at twice the insulation rating.

I would first unplug everything in the house, remove all light bulbs, turn on all switches, and megger each circuit at the panel. Anything that loads a circuit must be disconnected. Smoke alarms, etc. First test the circuit with a basic ohm meter, if it shows open then megger it. If it doesn't read open with an ohm meter, it certainly won't pass a megger test. Megger from hot to neutral, hot to ground, and neutral to ground. Grounds do not need to be disconnected.

Any circuit that reads less than a few milliamps is considered safe, it's pretty common to read less than 1 microamp.

Rob

P.S. The only circuits that should have been affected are ones that connected to things that were grounded by other than the electrical system. If the furnace is gas and its wire is cooked, check the gas piping carefully; it carried substantial current.
 
#8 ·
I'm sorry to hear about your troubles Jamie. At least now you have a real world example of what we have been telling in theory.

As others have said, megger, megger, megger! As far as the K&T circuits, it is unlikely they took any damage, because they are ungrounded and the current that did the damage was flowing on ground wires, otherwise the water pipe ground would not have caused any damage except at the water clamp.

Your old man was quite lucky he didn't get his face burned off!
 
#12 ·
Well, I have an update. I went over and did further investigation into what happened. The wiring in his house is sure a jumbled mess. I found that there is actually only one piece of romex that in all twirled around in the ceiling that melted. I also checked the old 4awg grounding cable that was removed and replaced to the water meter. The 4awg cable had almost 0 resistance, and it appears to be intact (it is in a mc type jacket).

After talking to my dad, and looking at where clamps were and such. I finally figured out what happened.

That 4awg wire shorted to leg of the panel, but the bond to the water meter stayed in tact, and was the path of least resistance to ground for the current (I assume it was the least, because the other choice would be to flow through the house wires, which are mainly ungrounded).

Upon closer examination once things were cleaned out, the water pipe was not actually severed as I first thought happened, It appears that the leak is not where the grounding clamp was, it was where the copper pipe jointed the lead pipe. So the current flowed through the copper 4awg to the copper pipe to the lead pipe -- lead pipe had more resistance, pipe heated up, and the joint loosened?? or caused pressure to build in the pipe and broke the connection? Possible?

As to the romex NM that was all burnt, I figured out that that cable much have been in direct contact with the ground wire to the water meter, which, must have become very very hot, which melted the romex outher sheathing, then caused a short in the cable.

Upon inspecting the box more, I highly suspect that the wires in the box are damaged from the heat that was produced by the fault.

In other areas of the house, I can find no evidance of any damage to the wires, other than in the panel and the one 20' piece of romex that is torched that was physically touching the 4awg ground wire.

I installed a utility outlet next to the panel and pluged in some extension cords. All appliances and computers tested thus far and just fine.

So, at this point, I suspect that he only damaged the cabled where they come into the panel and that one piece of romex

Do you think this sound right? Don't you think I would have found some evidance of damage elsewhere in the house or blown electronics if any amount of the current ended up flowing back into the branch circuits?

Thaks very much
Jamie
 
#9 ·
The actual current flow here is likely a lot less than you think.

As an example, lets assume the POCO transformer is 50 KVA. That's actually pretty good sized for a house, but somewhat normal for a bunch of houses fed from one transformer. The typical impedance for such a transformer would be around 4%. At 240 volts, 50 KVA = 208 amps. 208 amps divided by 4% = 5200 amps. This would be the current that the transformer could produce if the 240 volt side were shorted out at the terminals and the the high voltage side were maintained at rated voltage.

This 5200 amp figure is at the transformer, and doesn't account for current losses in the line from the transformer to the house.

In reality, most houses that are fed overhead, and not far from the POCO transformer will come out between 1000 and 4000 amps of short-circuit current. If the feed is underground, and the transformer is close to the house, figure 2000-5000 amps. It's extremely rare to have a single-phase service that can produce more than 10,000 amps.

It's amazing what a few thousand amps of current out of control can do though. Imagine what can happen in an industrial building with a 480 volt service capable of 30,000 amps!

Rob
 
#10 ·
It's amazing what a few thousand amps of current out of control can do though. Imagine what can happen in an industrial building with a 480 volt service capable of 30,000 amps!

Rob
Oh, brother! I wish I had some pics of some of the burn downs I've seen. The one that sticks in my mind in particular was when a couple of maintenance guys ran a lift up into a 12,470 V bus. It just showered molten metal what seemed like forever. The guys weren't hurt very badly because they were getting the hell out almost the time they realized what they had done! They had some pretty good burns but the lift was toast.
 
#11 ·
If I connect the hot and neutral on a circuit at the far end, and test from the panel, I should see a very very small ohm reading, even with a somewhat long run, correct? Would I just estimate the distance of the run and multiply it by 0.000078 per foot? and see if I get close to that reading on a ohm meter? How accurate of a test would that be?
The main problem here is not the open wires. They will be easy to find. The problem is the cables with wire intact but insulation damage that arc or short in the future. That is what a megger test should find. It is a test with each wire disconnected. High voltage is applied between the wires testing for arcing and current flow.
 
#13 ·
Homeowners should NOT be messing around in their panels.

I am glad that Dad is OK but...... what a dumbass.:jester:

I don't want to say that you encouraged him because of your new interest and experience with electrical but....:whistling2:

Again, I'm glad he's OK. Just have him call/pay someone to take care of his electrical. It aint rocket science but you NEED to know what you are dealing with.

I think that your assesment of the damage was probably correct. Tell Dad to do whatever it is that he does so he can be here to enjoy his grandkids.
 
#16 · (Edited)
Those findings make sense to me. I was trying to understand why a ground cable short to ground would burn up branch circuit wiring. I makes sense that a cable run beside the ground cable would burn up along with the ground.
The water pipe probably heated enough to melt the solder and let the water pressure blow the line apart.
Any chance you could post some pictures of this?
 
#21 ·
Those findings make sense to me. I was trying to understand why a ground cable short to ground would burn up branch circuit wiring. I makes sense that a cable run beside the ground cable would burn up along with the ground.
Tthe water pipe probably heated enough to melt the solder and let the water pressure blow the line apart.
Any chance you could post some pictures of this?
I am sure it would have all clicked for me much sooner if I had not been so freaked out by the whole event. As you can see in post #19, I explained in more detail where I was when this happened, and how it was a rather close call for me. :(

I did shoot some photos with my dad's camera last night, but left it over there, and there is no internet access or computer up and running yet. They are just using extension cords off of the utility outlet I installed late last night for them. (The licensed electrician was just going to leave all the branch circuits on that didn't have direct shorts on them - that scared me).

But will swipe his camera or memory card so I can get some posted in the next day.

Jamie
 
#18 ·
Jamie.,

I send you a PM to let you know that I am still in Paris France right now until end of this month.,


Now let get to the situation you have there .,

WOW.,, your papa is lucky he did not have the house burn down yet.

If I was still in Wisconsin., For sure I can zoom over and help ya.

that was pretty strong short current that make the copper solidering melt and BTW the soilder it will melt about 600~750°F depending on the " tin " itself.

Most POCO transformer can able crank out about 4 to 12 Kamps depending on size of transformer on resdentail area however in commercal the SCA { short circuit amps } it will be much higher it can have much as 30K or more depending on the size.

speaking for rest of wires IMO the best way is megger it.

I know not all electricians will carry this tester with them.
One thing I know with most homeowner insurance I am sure they have something to cover the damage but how much that part I don't know it pretty much up to them what they written in their policy but I am pretty sure they will cover most of the repair as need to.

I will start at the panel and work it way out after you check all the conductors to make sure they are not damaged at all or any burnt mark on them.

If you have any gas fired devices like furance , waterheater dryer etc etc check the gas system very carefully to see any burnt mark as well especally with SSCT { stainless steel corrated tubing }.

Merci,Marc
 
#19 ·
Homeowners should NOT be messing around in their panels.

I have to say that I really have a new perspective now that I didn't have before and I have to kind of agree with you. Even my old Pushmatic panel wasn't bad at all compared to my dad's mess and I've seen photos of worse. You have to be carefull enough in a good clean panel, but if there is stuff out there like my dads panel wow, you have to have some serious attention to detail to work in a live panel like that.

I am glad that Dad is OK but...... what a dumbass.:jester:
I don't want to say that you encouraged him because of your new interest and experience with electrical but....:whistling2:

Your right, he would not have been messing around in there if I hadn't pointed out that his ground wires in the house were ENERGIZED and that's why my mom was getting that little tingle when she touched the switch. So yes, I am responsiable for it in the sence and do feel bad that I was the one who pointed this stuff out. On the other hand one if one day my mom was walking in bare feet and the floor was wet when she touched a switch... It could have easily been much worse than what happened.

I am so lucky that he was using my pair of Klien insulated pliers or he very likely would have been electrocuted.


Again, I'm glad he's OK. Just have him call/pay someone to take care of his electrical. It aint rocket science but you NEED to know what you are dealing with.

I think that your assesment of the damage was probably correct. Tell Dad to do whatever it is that he does so he can be here to enjoy his grandkids.

That's kind of the problem with my dad, he has been a handyman his whole life and has always felt like he could do things like electrical himself. (he spent a lot of his life in construction, but is really too old to keep up with any larger construction jobs anymore). His work is normally very high quality, but He is very impatient and gets easily frustrated. I am on the other hand obsessive about the details, check everything atleast 3 times, and if I don't know how to do it, I ask / check on it.

I don't think I mentioned this before, this whole thing just scared the $*%# out of me. When this happened, (with the main out), I had a tone generator clipped onto the neutral bar in his panel, the other lead was clipped onto a branch circuit. I was in a upstairs office, At the exact moment this happened, I had just stuck the end of my metal probe on my tone generator into the hot side of a outlet, with the speaker on high. Man did that freak me out, I almost droped dead on the spot, (I thought how the is there this horriable loud booming voltage hum when I have the main pulled, I thought, my dad knew very clearly not to put the main back in, what the $%* ) it was one horrible humming buzzing noise. I am really lucky that the wires that he burned through and shorted out in the panel were not the wires I had the probe on or I could have been electrocuted with my probe... Yet another good lesson, always tag and lock out your work if your counting on it being de-energized. I knew he was not going to put the main back in, he knew I was testing.

He has an insurance adjustor comming out tommrow, and they are hopefully going to pay for someone to come and clean up this whole mess for him.

Jamie
 
#25 ·
Hi Marc;
I send you a PM to let you know that I am still in Paris France right now until end of this month.,
Thanks for sending me the message.

that was pretty strong short current that make the copper solidering melt and BTW the soilder it will melt about 600~750°F depending on the " tin " itself.

Never have I seen a meter spin so fast. It ran like that for a hour. I wonder what the power bill is going to be!!! since it was unfused, I suppose it could have been well over 200 being used. ouch!

Most POCO transformer can able crank out about 4 to 12 Kamps depending on size of transformer on resdentail area however in commercal the SCA { short circuit amps } it will be much higher it can have much as 30K or more depending on the size.

He is over off Wisconsin, In neenah, just a block from down town. So I am not sure what size transformer he would have.

speaking for rest of wires IMO the best way is megger it.

I know not all electricians will carry this tester with them.
One thing I know with most homeowner insurance I am sure they have something to cover the damage but how much that part I don't know it pretty much up to them what they written in their policy but I am pretty sure they will cover most of the repair as need to.

He is talking to the insurance in the AM. If they decide it is covered, he has up to 240,000 to cover damages.

I suspect that someone will come in and megger for him due to the situation. However, I'd like to get myself a megger. I posted a message about a couple models I am looking at.

Do you have a megger you use?

I will start at the panel and work it way out after you check all the conductors to make sure they are not damaged at all or any burnt mark on them.

If you have any gas fired devices like furance , waterheater dryer etc etc check the gas system very carefully to see any burnt mark as well especally with SSCT { stainless steel corrated tubing }.

Merci,Marc

All black iron, no signs of damage there. (one whip upstairs on stove, i'll double check that one for safety) HVAC guy was out and went over it, it had stopped working. Turn out the only problem was that when my dad wired the furnace to the extension cord for a temp hook up, he reversed the polarity on the connections. For some reason this a problem for the furnace and will not allow it to start. But the HVAC guy went over all the furnace stuff and connections and I inspected the rest of the gas pipe.

I wanted to get in there more today and pull more stuff apart and look at more things, but my dad needs to wait till tommrow to see what decisions the insurance adjustor makes about the damage and what they are willing to pay for.

Thanks Marc.

Jamie
 
#27 ·
Update

Update: The insurance will pay for damages, however, they don't want to pay to bring stuff up to current code. i.e. rewire circuits with a ground. What an expensive mess this is going to be. I hope that if anyone reads this they will think twice about working around unfused service if they are not absolutely certain they know what they are doing and the risks of that kind of work.

He found an electrician that will megger the wires, and should be coming out tomorrow. Then we will find out for sure how extensive the damages where.

I have my camera and the car and will snap some more photos when I go over and post them later on.

Thanks again guys.

Jamie
 
#29 ·
Update: The insurance will pay for damages, however, they don't want to pay to bring stuff up to current code. i.e. rewire circuits with a ground.
Since it is impossible to repair without meeting code I suspect they are actually financially responsible for whatever expenses are required to repair the damage including anything required to meet your local codes that are in force for the type of repair work being done.

For example, if your local code allows 2 wire romex to be used for repair of existing 2 wire circuits then the insurance company could limit their financial responsibility to that (I doubt your code allows that). But if your code requires that all circuits being repaired be upgraded to current codes then I think the insurance company is responsible for that entire cost.

You might want to push back at the insurance company.
 
#30 · (Edited)
>>> ... why a ground cable short to ground would burn up branch circuit wiring.

One example:

Let's say the water heater has an electronic ignition or an electric vent damper. It is served by a branch circuit with ground wire connected to its chassis. Then fault current flows through the water pipes, reaches the water heater, and uses that #14 gauge or so ground wire to get back to the panel ground. That part of the branch circuit in question back to the panel is now fried by the overloaded and therefore overheated ground wire.

Current is not going to flow through all the pipes, just those between the energizing point (the clamp) and where there is existing metal to metal connection to a ground such as described above. But a voltage "potential" does exist throughout the plumbing system. A person touching any water pipe, faucet handle, etc. and whose other hand or feet, etc. are grounded can be electrocuted.

Since a pipe joint melted open, that is evidence a lot of current went "thataway".

By the way, the voltage involved was 120. Only one of the unfused terminals of the 120/240 volt service was touched by the #4 wire.
 
#33 ·
Well I wonder what the insurance company does about wiring that is so sub standard it doesn't even come close to any codes now or ever. I gutted all the EMT today. I found some really scary stuff. I forgot my camera over there.

The 1/2" emt run to the AC contained 2 #12 and a insulated ground wire, all THHN. It appears at one point the THHN was damaged due to a bad pull. That must have arced and about 20' of the run melted and fused together all 3 strands of the THHN. If it wasn't in EMT the house would have most certinly been on fire if that happened.

Some of the things I have found are too scarey to describe, will have to post photos.

The electrician that is going to megger the upstaris circuts didn't make it today, but hopefully tommrow.

If what happened in that conduit to the AC happened anywhere else in the house... Well it could have happened partially and just managed not to start a fire, but the wires could still be in very bad shape.

I found that all the Knob and tube is feed off of Romex. Atleast some of the junctions to romex are burried in the walls....:whistling2:

Don't if it I should laugh or cry. :laughing::furious::(

Much of this was done by the previous owners, and has been this way for over 3 decades.

Jamie
 
#35 ·
I gutted all the EMT today.
I know you are anxious, but you might be hurting your ability to make a larger insurance claim here for bringing all the damaged circuits up to code.

Was there already a permit pulled for work at his house before the accident?

If so, the insurance company is going to be more likely to see your claim as a way to fund the work you were already planning on doing.
 
#34 ·
Jamie.,

Thanks for letting us know up the speed with the damage ya got on your father's house.

Speaking of Megger I have Fluke Megger { yes there is serveal verison on market } and I got a simple megger which it will give me go or no go with the cables or conductors { It a Amtech but not sure if the company still in bussiness or not }

Merci,Marc
 
#49 ·
I agree. This would be a perfect time for a total rewire. Best advice I can give here is to check all of your smoke detectors immediately, and add as many as you need to bring the whole house up to spec.
I would shut off all breakers that are not absolutely necessary, and only keep them on during the day, when you're home. Perhaps installing some AFCI would be in order.
 
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