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Fixed it

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My Old Tools

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I had been noticing for awhile that we had an LED lamp that flickered or dimmed occasionally. Then I noticed it seemed to correlate to a change in frequency of the ice maker compressor noise. I started looking for it today. I pulled the front off our main panel (20 year old Square D). I immediately noticed one of the main feed wire looked discolored on one side and it felt warm. I killed the main and took a half turn on the lug. Thought that was it. Turned on the power and the light flickered again. Started to pull the breaker for that circuit when I saw sparks come from behind that main lug. I killed power again and pulled the incoming line off the lug and I could see the top of the buss bar discolored behind it. I worked the lug around a bit and got it freed up. Re-tightened the lug on the feed line and really cranked it down. I think i have it now. That panel has been in place at least 20 years.
 
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mm08822

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Keep an eye on it once you have sustainable loads............electric heaters or more likely ac.
 
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PCustoms

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My Old Tools said:
started looking for it today. I pulled the front off our main panel (20 year old Square D). I immediately noticed one of the main feed wire looked discolored on one side and it felt warm. I killed the main and took a half turn on the lug. Thought that was it. Turned on the power and the light flickered again. Started to pull the breaker for that circuit when I saw sparks come from behind that main lug. I killed power again and pulled the incoming line off the lug and I could see the top of the buss bar discolored behind it. I worked the lug around a bit and got it freed up. Re-tightened the lug on the feed line and really cranked it down. I think i have it now. That panel has been in place at least 20 years.
Click to expand...

Wasn't this hot as you did the work?
 
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PCustoms

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wyliesdiesels said:
Did you cut the smashed strands and start with fresh wire?

Did you use a torque wrench? Doesnt sound like it. Lugs have specific torque values. Under torquing is just as bad as over torquing.
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I got up to grab a drink and when I got back you already posted my next thoughts. Cranking down on wire that was already fubar did more harm then good
 
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My Old Tools

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wyliesdiesels said:
Did you cut the smashed strands and start with fresh wire?

Did you use a torque wrench? Doesnt sound like it. Lugs have specific torque values. Under torquing is just as bad as over torquing.
Click to expand...
No. It tightened on the wire without fully clamping the buss bar. The lug was burred or binding somehow. After I loosened it completely and worked it around a bit to get it moving, I locked it back down. Wire is now cool and everything is stable. With a 5 inch Allen, I'm pretty comfortable that I didn't hurt it.
 
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mm08822

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A pic would be good to see how far the heat traveled in both directions.

What color is the lug and what is the condition of the conductor insulation?
Is this Al or Cu conductor?
Was the set screw in the lug galling as you turned it?
 
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wyliesdiesels

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My Old Tools said:
No. It tightened on the wire without fully clamping the buss bar. The lug was burred or binding somehow. After I loosened it completely and worked it around a bit to get it moving, I locked it back down. Wire is now cool and everything is stable. With a 5 inch Allen, I'm pretty comfortable that I didn't hurt it.
Click to expand...
That is not the proper procedure for torquing a lug….
 
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Norcal

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If it was the main panel, the conductors entering the main breaker have no overcurrent/short circuit protection at all, the consequences of a screw up is very high.
 
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reader2580

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wyliesdiesels said:
Did you use a torque wrench? Doesnt sound like it. Lugs have specific torque values. Under torquing is just as bad as over torquing.
Click to expand...
I’m curious, do you actually look up the torque values for every single thing you tighten down, and use a torque wrench on them all? I think I would spend more time trying to find torque values for everything than actually doing the work.

My understanding is torque screwdrivers are required in the UK.
 
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mike93lx

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reader2580 said:
I’m curious, do you actually look up the torque values for every single thing you tighten down, and use a torque wrench on them all? I think I would spend more time trying to find torque values for everything than actually doing the work.

My understanding is torque screwdrivers are required in the UK.
Click to expand...
Electrical stuff is often (always?) labeled with the torque spec
 
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manwithtools

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reader2580 said:
I’m curious, do you actually look up the torque values for every single thing you tighten down, and use a torque wrench on them all? I think I would spend more time trying to find torque values for everything than actually doing the work.

My understanding is torque screwdrivers are required in the UK.
Click to expand...
As @mike93lx said, the components (breakers, neutral and ground bars, bus lugs, etc.) are already labeled with the correct torque required. Technically every termination has a torque spec, including outlets and switches. Most electricians don't torque outlets and switches, but they should. Good electricians do torque breakers and panel terminations at the very least.
 
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My Old Tools

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When I said our main panel, it is a sub now. When the house was built it was the main, and still has 95% of the breakers. So yes, I killed power to the panel. I'm a EE and I've been doing my own electrical work for 50 years. Not a professional electrician, but adequate. I'll take a slightly over torqued set screw over a loose arcing connection all day, every day. As I said, the wiring is now cool (copper by the way) and the lights no longer flicker, so I'll claim success.

After my last house that was built by a professional electrical contractor that did high end subdivisions around Dallas, I think my skills are ok. That 1/2 million $ house had undersized breakers on one AC unit, a wire not even tightened on the breaker on another AC unit, and a couple of plugs he never bothered to connect at all, even though they were wired. It was his personal home and 2 years old. Bought it in 2009 when he went broke in the housing crash.
 
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wyliesdiesels

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reader2580 said:
I’m curious, do you actually look up the torque values for every single thing you tighten down, and use a torque wrench on them all? I think I would spend more time trying to find torque values for everything than actually doing the work.

My understanding is torque screwdrivers are required in the UK.
Click to expand...
I do and they arent hard to find.
 
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My Old Tools

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I ended up changing out the 200 amp main disconnect breaker that had the lugs. That one lug had heated, sputtered, and welded until it ultimately was no longer safe. It just wouldn't make a solid connection anymore. Fortunately HD had a QOM2200VH on the shelf, so I was there before 7 the next morning to get it. 30 minutes later I feel much better about it.
 

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dave*99

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My Old Tools said:
I ended up changing out the 200 amp main disconnect breaker that had the lugs. That one lug had heated, sputtered, and welded until it ultimately was no longer safe. It just wouldn't make a solid connection anymore. Fortunately HD had a QOM2200VH on the shelf, so I was there before 7 the next morning to get it. 30 minutes later I feel much better about it.
Click to expand...
I'm curious as to how you got from "fixed it" to reopening and changing the breaker? GJ guilt? Curiosity? Flickering?
 
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mm08822

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Open the housing on the old main cb and see how far the heat damage traveled.

Try a 4" grinder with cutoff wheel to delicately open it up.
 
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PCustoms

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My Old Tools said:
Pretty solid now. Why would you expect something else?
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My industry experience and thermography certifications.

That little bit that looked bad in the first place was just the top of the damage that occurred due to the original loose connection. You got a little more of it by swapping the breaker, but you. Certainly haven't posted enough for anyone to tell if it ended there. Or if the wire upstream needs more work.

Frankly for what you paid for that main breaker it might have been easier/cheaper to swap the panel. Assuming the same panel is available it could have been as easy as swapping the guts.
 
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My Old Tools

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PCustoms said:
My industry experience and thermography certifications.

That little bit that looked bad in the first place was just the top of the damage that occurred due to the original loose connection. You got a little more of it by swapping the breaker, but you. Certainly haven't posted enough for anyone to tell if it ended there. Or if the wire upstream needs more work.

Frankly for what you paid for that main breaker it might have been easier/cheaper to swap the panel. Assuming the same panel is available it could have been as easy as swapping the guts.
Click to expand...
Panel is fine. No sign of any heat beyond that one lug on the breaker. The way those breakers mount, the whole thing would have to melt down to pass any significant heat through to the rest of the panel.
 
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PCustoms

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My Old Tools said:
Panel is fine. No sign of any heat beyond that one lug on the breaker. The way those breakers mount, the whole thing would have to melt down to pass any significant heat through to the rest of the panel.
Click to expand...
I hope so.
 
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