What the????

[220/221]

Service call Monday.

Microwave circuit issure. One micro dead, the new one acting up. Sparks coming from c top recep.

Instant diagnosis, MWBC w/ open neutral.

Get to the job and the house is 5 years old. Homeowner replaced GFCI and breaker. Still has issues. He calls electrician via website. Sparky says "loose wire" and bills $125. Apparently Sparky didn't open the panel cover or he would have certainly seen this.

http://i8.photobucket.com/albums/a8/JohnC1952/DSC01741.jpg

The lugs were ALL loose but I'm not sure how this one area was so overheated. Conductors were phased properly so...???

Am I missing something?

I tightened everything, cut off the ends of the affected neutrals and re connected.

[kspifldorf]

This may be ridiculous, but I like to go through and retighten all the connections in my own house the first couple of years. I've never failed to find one I didn't like. Thats just scary!!!

[ironman3452]

the new home i had built, was to be done correctly, 2 years latter had problem with the light in the dinning room, it would flicker then, come back brighter, went out to panel, turned off main and checked, all terminals inside were loose, i took my torquing driver and went thru the panel, all were loose and not torqued to specs, well to make a long story short, light now workes very well, so i think it's not a bad idea to make sure all wiring is tight.

[kspifldorf]

Checked third and fourth years everything fine as well. I know we have these guys at the plant do retourqing biannually as a PM, then document them for later IR scans yearly.

[don_resqcapt19]

Checked third and fourth years everything fine as well. I know we have these guys at the plant do retourqing biannually as a PM, then document them for later IR scans yearly.
Retorquing is not recommend and is often the cause of failed connections.

[Sierrasparky]

Retorquing is not recommend and is often the cause of failed connections.

why is that..

[kspifldorf]

If there loose with your screwdriver, then what?

[macmikeman]

The top three or four neutral conductors in the neutral bus do not appear to be affected. Lower down, they all have damage except perhaps the very bottom one. Inspect the busbar carefully to check for a crack in the metal and subsequent separation or increase in resistance. You may be able to take an ohmmeter and get different resistance readings checking the upper and lower portion of that busbar in relation to the main neutral lug. There also could be problems in the neutral connections upstream, even before the conductors get to the building. Thats all I could think of if the conductors are all phased properly and there is no multiwire branch miswiring.

[quogueelectric]

The bad circuit was probably just about burned through and he probably just trimmed back retightened and closed the panel wrote out his bill. probably never entered his mind to check other wires for tightness.

[220/221]

Inspect the busbar carefully to check for a crack in the metal and subsequent separation or increase in resistance


I did this but only visually and by grabbing and pulling on it.

I did notice that the wires above and the one below were not affected but didn't understand why. The bus goes upward, then bolts to anothr piece going across to the other side. I assumed that if there was a fault up stream that it would show itself there.

Crap....am I gonna have to go back and look deeper???


The bad circuit was probably just about burned through and he probably just trimmed back retightened and closed the panel wrote out his bill. probably never entered his mind to check other wires for tightness.

He was there only a few days before I was. This condition was not fresh. I am pretty sure he didn't even open the panel.

[aline]

He was there only a few days before I was. This condition was not fresh. I am pretty sure he didn't even open the panel.
As a courtesy I pull the panel covers off and inspect and check the connections on every residential service call I go on. It's supprising how often I find loose connections. Some don't appear to have ever been tightened down.

Doing this helps give the customer the feeling that they're getting more for their money than just reseting a GFCI or something simple, handing them the bill and getting out of there as fast as possible. This can also lead to more work. It's an opportunity to mention whole house surge protection as well. Also while I'm there I put a sticker on the panel.

[Sparky555]

The lugs were ALL loose but I'm not sure how this one area was so overheated. Conductors were phased properly so...???

Am I missing something?

I tightened everything, cut off the ends of the affected neutrals and re connected.

I don't believe you missed anything. Loose connections get hot---increased resistance. I have a collection of things burned by loose connections.

Dave

[peter d]

I don't think you're seeing anything unusual, just intense heat build up from the loose connections. Remember than an arc is ball of plasma, no matter how small it is. Plasma is pretty hot. :)

[cowboyjwc]

Retorquing is not recommend and is often the cause of failed connections.


why is that..

When you torque a screw at X inch pounds, if you apply the wrench to it again it does not show you that it is torqued at X inch pounds, it trys to torque it at X inch pounds again. So you are over torquing it and actually can strip out the screw or damage the conductor.

When an inspector wants to check that you have torqued all your bolts, he really needs to be there when you are doing it originally.

[electricmanscott]

Get to the job and the house is 5 years old. .


I bet those were loose connections from day one. I see it often in newer homes. Intial installer probably stripped all the conductors at once, stuck them into the terminals and didn't tighten them all.

Slow down and pay attention!

[don_resqcapt19]

The torque specs for mechanical terminations take into account the creep or cold flow that takes place when you apply pressure to a soft metal like copper or aluminum. If you come back and retorque the connection at a future date you are causing additional cold flow and at some point this results in a poor connection. The following is from the Southwire Power Cable Manual.
4) Most importantly, do not re-torque the terminations as part of routine maintenance. As with copper conductors, repeated tightening of any set-screw connections can result in the eventual “biting” through the conductor causing the termination to fail.

[boboelectric]

Service call Monday.

Microwave circuit issure. One micro dead, the new one acting up. Sparks coming from c top recep.

Instant diagnosis, MWBC w/ open neutral.

Get to the job and the house is 5 years old. Homeowner replaced GFCI and breaker. Still has issues. He calls electrician via website. Sparky says "loose wire" and bills $125. Apparently Sparky didn't open the panel cover or he would have certainly seen this.

http://i8.photobucket.com/albums/a8/JohnC1952/DSC01741.jpg

The lugs were ALL loose but I'm not sure how this one area was so overheated. Conductors were phased properly so...???

Am I missing something?

I tightened everything, cut off the ends of the affected neutrals and re connected.
What about the sparking receptacle?

[LarryFine]

Looking at this pic again, it looks like the head of screw with no conductor is cooked, and the very bottom wire is too much whiter than it's neighbor. Plus, the wires above and below this hole are the most damaged.

If I were to take an educated guess, I'd say the wire on the bottom was in the now-vacant hole, and was shortened, re-stripped, and re-terminated.

[mivey]

Reasonable. But why the ash on the whitest wire and why is the burnt spot behind the 3 upper wires instead of the hole?

[jmsbrush]

why is that..
110.3(b) Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

Breakers, switches, recpt.. lugs and ect have tork requirements. When you do not follow the guide lines fires can occur.

[220/221]

What about the sparking receptacle?

The homeowner said HE replaced it. The line side was marked with scotch tape. I took it apart and assured that the connections were good and proper. It was the home run. I don't know if the other electrician looked there or not. All I could get out of the HO was "he said it was a loose wire" and "he talked a lot".





Looking at this pic again, it looks like the head of screw with no conductor is cooked, and the very bottom wire is too much whiter than it's neighbor. Plus, the wires above and below this hole are the most damaged.

If I were to take an educated guess, I'd say the wire on the bottom was in the now-vacant hole, and was shortened, re-stripped, and re-terminated.

I noticed that also and the bottom white wire WAS one of the 3 wire neutrals but A) it was one of the loosest ones and B) would ANYONE just repair ONE burned wire? If they did, wouldn't they tighten the lug?

Also there is a lot of burned debri on that clean bottom wire. The HO claimed the other guy was there a few days before me.

Maybe there was no other sparky???

Also, after my repair you can still see discolored insulation. The bottom on is pretty white.

http://i8.photobucket.com/albums/a8/JohnC1952/DSC01743.jpg

[frizbeedog]

I bet those were loose connections from day one. I see it often in newer homes. Intial installer probably stripped all the conductors at once, stuck them into the terminals and didn't tighten them all.


I'm going with this diagnosis as to the cause.

[quogueelectric]

I'm going with this diagnosis as to the cause.
I second the nomination floppy ears.

[frizbeedog]

I second the nomination floppy ears.

I'll third your second there T-Bone.

[LarryFine]

You guys are a bunch of animals! :grin: