This is why proper torque is important.
- Thread starter wyliesdiesels
- Start date
zmaxmotorsports
Well-known member
Better yet pitch the general panel and replace it with something better,maybe a 40 year old fed pac panel.
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OP
wyliesdiesels
Well-known member
Better yet pitch the general panew and replace it with something better,maybe a 40 year old fed pac panel.
Wish i could but no way thats happening.
Its a flush mount in stucco.
Where did i say it was overtightened?
If anything it was under tightened.
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OP
wyliesdiesels
Well-known member
BTW panel is only 12 yrs old.
rlitman
Well-known member
Why are you drilling it out? You can rest assured that the melted lug damaged at least the wire underneath it. And also cooked the closest insulation.
I'd be cutting back a bit instead. Can't you find an inch of wire to spare?
I'd be cutting back a bit instead. Can't you find an inch of wire to spare?
OP
wyliesdiesels
Well-known member
Negative.
Thats factory installed cut to length wire.
There is no slack.
Im trying to avoid pulling everything out of the whole panel as thats what i would most likely have to do to replace the wire from the meter to the breaker since it sits clamped behind the bus bar bracket.
The PoCo has limited service hours to disconnect and reconnect(8-3:30) and they rarely get there on time. If Im not ready to heat the panel backup by 3:30, homeowner has no power for the night.
But yes u may be right- the insulation is probably cooked and I may have to.
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rlitman
Well-known member
Ouch!
Well, the insulation itself can be repaired. A little heat shrink may be all it needs.
But you won't know how the copper looks until you get it out of that lug. I guess a lot depends on how long the copper was hot. At the temperature of molten aluminum, plain copper oxidizes pretty quickly though.
Best of luck, but you know as well as I that it doesn't look good. Wouldn't it be nice if you could buy a wire stretcher?
Well, the insulation itself can be repaired. A little heat shrink may be all it needs.
But you won't know how the copper looks until you get it out of that lug. I guess a lot depends on how long the copper was hot. At the temperature of molten aluminum, plain copper oxidizes pretty quickly though.
Best of luck, but you know as well as I that it doesn't look good. Wouldn't it be nice if you could buy a wire stretcher?
bobmulry
Well-known member
Hi Guys,
When I worked for a living, part of our PM's included checking lug tightness.....
At home I kind of check all the lugs about once a year.......
They also tend to loosen up on their own......
Just sayin'
Bob
When I worked for a living, part of our PM's included checking lug tightness.....
At home I kind of check all the lugs about once a year.......
They also tend to loosen up on their own......
Just sayin'
Bob
barnjunkie
Well-known member
Looks like the insulation was not stripped back far enough.
OP
wyliesdiesels
Well-known member
Insulation stops just before the lug. Its fine.
You Cant tell at the angle the pic was taken.
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Actually the correct way is to torque to specs and leave it alone, by torquing to specs means using a proper tool, not a WAG that it's tight enough, as the manufacturer has determined the correct amount.
I hate to break it to you, but you're going to want to cut the wire. It's very bad practice to reterminate a wire after it has been used in a mechanical connector. Solid wire is usually ok, but any time you tighten down a stranded wire, you are doing some damage to the strands. Not to mention, if the terminal melted, there's most likely some damage to the wire itself.
Also Norcal is correct. Lugs are designed to be a single torque and leave alone. Repeated tightening can also damage wire strands and cause a failure over a long period of time.
Also Norcal is correct. Lugs are designed to be a single torque and leave alone. Repeated tightening can also damage wire strands and cause a failure over a long period of time.
checkthisout
Well-known member
- Joined
- Sep 5, 2008
- Messages
- 5,232
Always remember,
TIGHT IS RIGHT!
With my own projects and helping various friends I have often found that feeds to main breaker panels are loose.
Isn't that a function of Aluminum wire? It loosens up over time and must be re-torqued. That's why they quit using it for branch circuits right?
At my current house I ended up having to replace the breaker because the high resistance caused by the loose connection overheated the breaker. It caused it to pop a few times during high load I.E. furnace and range running before I had a chance to investigate and find out the cause.
TIGHT IS RIGHT!
With my own projects and helping various friends I have often found that feeds to main breaker panels are loose.
Isn't that a function of Aluminum wire? It loosens up over time and must be re-torqued. That's why they quit using it for branch circuits right?
At my current house I ended up having to replace the breaker because the high resistance caused by the loose connection overheated the breaker. It caused it to pop a few times during high load I.E. furnace and range running before I had a chance to investigate and find out the cause.
My thoughts also. Hot enough to melt a lug, it was probably hot enough to damage the breaker.
If the lugs are torqued to manufacturers specs, it should not be retorqued, over tightening is as bad as not enough, and not using the proper tool & guessing that it's "tight enough" is improper also.
sberry
Banned
This would depend on how good the guess was wouldnt it? I agree they should not keep cinching lugs or screws down on aluminum wire but it doesn't hurt to check them and they should be snugged if they are loose.
Lets see, this wire is loose,,, lets leave it that way after all it was torqued 20 years ago. To top it off a dry squeaking screw doesn't torque proper anyway and the only reason there isn't a procedure to lube them is they cant get all the chimps to do it the same, pretty much the same for car wheels so lets dumb it down another notch and use a no0ther tool to tell the installer how far to turn a common bolt and hope for the best that it actually clamped with enough force to hold this soft pressure connection.
I seen that test by sparlies, 1 out of 10 had any concept what 25 # was right, the one had it perfect and most from 7 to 12#, a couple at 15.
Its obvious as daylight that while they know where the wires go there is some step missing in general mechanical training in regards to threaded connections.
As I mention in another thread, the inspector checked the last set I did, he checked them the same way I installed them, with a big ole fat Klien screwdrive with both hands on is just short of stripping the screw
Lets see, this wire is loose,,, lets leave it that way after all it was torqued 20 years ago. To top it off a dry squeaking screw doesn't torque proper anyway and the only reason there isn't a procedure to lube them is they cant get all the chimps to do it the same, pretty much the same for car wheels so lets dumb it down another notch and use a no0ther tool to tell the installer how far to turn a common bolt and hope for the best that it actually clamped with enough force to hold this soft pressure connection.
I seen that test by sparlies, 1 out of 10 had any concept what 25 # was right, the one had it perfect and most from 7 to 12#, a couple at 15.
Its obvious as daylight that while they know where the wires go there is some step missing in general mechanical training in regards to threaded connections.
As I mention in another thread, the inspector checked the last set I did, he checked them the same way I installed them, with a big ole fat Klien screwdrive with both hands on is just short of stripping the screw
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sberry
Banned
I watched a guy the pother day, sposed to be a journeyman, tighten down 3 rusty 3/4 bolts with no oil, I asked and he reasoned it may attract dirt but did them with a squeal and a 1/2 hand ratchet. Clamping power was almost nothing.
Adam C a member here and I disagree about the need for a Snapon ratchet but the place we are on the same page with is bolt installation and he is way more qualified than I am and can probably splain it better and have the math to prove it.
It really took me a bit to make it a reflex to think about it in terms of clamping over simple torque which is a way, quite primitive really but the best field method we generally have to measure it.
I am all for mfg instructions. We found an engine a while back, loose, turns out we think someone read the book wrong but we have had as good results for a journeyman to had torque the heads on the littles suggers. Only part we used a wrench was rods and they are such pristine bolts with fine threads it is probably pretty accurate.
Adam C a member here and I disagree about the need for a Snapon ratchet but the place we are on the same page with is bolt installation and he is way more qualified than I am and can probably splain it better and have the math to prove it.
It really took me a bit to make it a reflex to think about it in terms of clamping over simple torque which is a way, quite primitive really but the best field method we generally have to measure it.
I am all for mfg instructions. We found an engine a while back, loose, turns out we think someone read the book wrong but we have had as good results for a journeyman to had torque the heads on the littles suggers. Only part we used a wrench was rods and they are such pristine bolts with fine threads it is probably pretty accurate.
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Actually, if you found a terminal that was loose after 20 years, any manufacturer would tell you to replace the terminal, and cut and restrip the wire. You don't know how many times it's been tightened, and the wire could be seriously compromised.
As for lubing threads, a lot of design work goes into the proper torque. If you put lubrication on the screw, you actually are supposed to decrease the amount of torque you put on it. A lubed screw has less friction, and thus a higher clamping force. If the connector is designed and spec'ed to be torqued without lube, you are over compressing the wire, and could cause damage.
Electrical connectors are made of copper and aluminum, and are a different deal than the steel bolts in an engine.
ishiboo
Well-known member
I purchased a nice 3/8" torque wrench just because I had a lot of lugs to do. Better safe than sorry. When I had 40 outlets to do in my upstairs after I finished the renovation, I bought a Wiha torque screwdriver. For electrical work it seems to take ZERO more time to torque stuff properly and then you don't have to worry about it.
ishiboo
Well-known member
I think this is BS. If it needs to be torqued to 28 ft-lbs, and you come back and retorque it a year later to 28 ft-lbs... what's the difference? You are only changing ANYTHING if it is BELOW 28 ft-lbs of torque when you go to retorque it. Retorque does not mean you are over-tightening it.
That said, without the vibrations, shock loads and everything else things like lug nuts are subject to, I think a properly torqued lug probably never has to be re-torqued.
sberry
Banned
I would tighten a loose screw, how lo g you actually been doing this work? Some rudimentary apprentice level instruction will include the the idea isn't to cut the wire.
I can't imagine leaving a loose conection in a panel where a simple twist of a screw will do. But,,,,, spose a guy could get on the phone and start looking up specs, calling engineers and getting several opinions.
I can't imagine leaving a loose conection in a panel where a simple twist of a screw will do. But,,,,, spose a guy could get on the phone and start looking up specs, calling engineers and getting several opinions.
sberry
Banned
I been at this long enough to see a lot of old broke seized ****, almost none failed where it was fussed over when it was installed. Not some or the "one i did" but a pretty good poop including some of my own installs from 38 years ago, replaced one of them from corrosion, never had a problem with 1 with a greasy screw including those with aluminum conductors. None, not a few less, none, dozens of dry seized where the well guy couldn't even ground it as the bar is so corroded.
I have significant research and testing to prove you wrong.
Aluminum connectors are a funny animal. You can torque them down, and then check them 5 minutes later, and they are significantly looser than they were to start. This is known to the manufacturers, so it is designed around.
If you went back and checked it, it would indeed be lower than what you set it at, every time you check it. This is because the aluminum actually slowly yields from the pressure. If you keep re-torquing it, you continually deform the conductor, and eventually will cause it to fail.
OP
wyliesdiesels
Well-known member
Have u seen any evidence that copper can suffer from the same albeit much less since its harder??
Copper does to some extent, but less. It is still considered best practice to only torque connectors once.
sberry
Banned
People have trouble with the concepts of a little and a lot too. I agree it aint a bulldozer and doesn't need to be farmer tight. You can feel aluminum a lot in 24 hrs. But most people are not strong enough to damage a number 2 alum with a screwdriver handle.
The lineman has 3/8 ratchet for 200A service and guys that see 1000's of connections comment on the light greased bolts I got in the base for them.
100A panels have slotted screw mains. Cutting them off isn't a problem and the inspector wasn't checking them to see if they were too tight.
The lineman has 3/8 ratchet for 200A service and guys that see 1000's of connections comment on the light greased bolts I got in the base for them.
100A panels have slotted screw mains. Cutting them off isn't a problem and the inspector wasn't checking them to see if they were too tight.
sberry
Banned
Here is another thing, because yo go back to check a screw doesn't mean you have to give it another big ole pull. Would yo not want to know?
They tell you to recheck the wheels in 500 miles,,, what do you do if you find one loose? We found with alum wheels if I want to pay attn. can hit them up about perfect with 2 passes but just hitting them again in the 3rd drives them too tight. I did a steel wheel this morning and they needed 1/8 more turn than I gave them with a battery gun.
Over tightening not quite such an issue by hand as repeated impacting. Some meter base connections are clamps. You could over stress a clamp but wont hurt the wire. But there are 2 reasons they are lose, they were not twisted tight to start or were not clamped tight due to bolt seizure.
They tell you to recheck the wheels in 500 miles,,, what do you do if you find one loose? We found with alum wheels if I want to pay attn. can hit them up about perfect with 2 passes but just hitting them again in the 3rd drives them too tight. I did a steel wheel this morning and they needed 1/8 more turn than I gave them with a battery gun.
Over tightening not quite such an issue by hand as repeated impacting. Some meter base connections are clamps. You could over stress a clamp but wont hurt the wire. But there are 2 reasons they are lose, they were not twisted tight to start or were not clamped tight due to bolt seizure.
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ishiboo
Well-known member
That's fine, but you are testing and re-torquing once with a calibrated instrument so you know its correct. If you replaced a breaker, do you cut off the already torqued strands for this reason? (Assuming the strands are not all screwed up, which sometimes happens with small set screws) Same thing.
bczygan
Well-known member
Creep!
Not calling you a name! It's what aluminum does.
Not calling you a name! It's what aluminum does.
sberry
Banned
If it looked boogered I would fix it, pretty simple really. But the torque problems among the diy that don't use the tool are not coming from cutting conductors but too loose.
I agree with this hence my story about the aluminum wheels. Different though than tightening a loose connection we may find.
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I have taken down old installations and reduce bits and sections of them. Rarely did I ever find anything loose or falling apart with a light pull.
In fact it was rust or corrosion that made them harder to undo and sometimes directly into the recycle pile.
In fact it was rust or corrosion that made them harder to undo and sometimes directly into the recycle pile.
LS6 Tommy
Well-known member
It wasn't too tight, it was too loose...
EDIT-
Sorry I just saw where that was brought up...
Tommy
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bobmulry
Well-known member
I don't do WAG's.............
We didn't work that way........
ALL equipment that used lug connections had the torque spec inside the cover...
We either used a torque wrench or a torque screwdriver......
Never been a WAG type of guy................
Bob
PS:
Yes some of the lugs would make up a little.......
alfredeneuman
Well-known member
According to the folks at the Aluminum Association
See question 10.
http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical
Retorquing isn't necessary
See question 10.
http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical
Retorquing isn't necessary
rlitman
Well-known member
Ok, but it also says:
"Connections should only be tightened if there is evidence of a loose connection."
Now how would you determine if the connection is loose?
I will add this however. If a dry connection is found to be loose, whether it be in copper or aluminum, the heat seen at the loose connection often leads to oxidation, and simply re-tightening it may no longer be sufficient. If I find a hot connection (I feel the need to point out that I have NO experience with aluminum wiring here, just copper and more exotic stuff, and aluminum lugs), I'm not simply going to turn a screw and walk away.
Also, one scary scenario I've seen, is when someone loses the screw from an aluminum terminal, and replaces it with a hardware store bought screw. Aluminum terminals always use aluminum screws, so that the parts expand and contract thermally together, which prevents thermal cycling from loosening the joint. Substitute a steel screw, and you WILL see failures.
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Copy & paste of Q10
Q10) Do aluminum connections need to be periodically tightened to maintain a good electrical connection?
No. Connections on either aluminum or copper should not be retightened after installation following manufacturers’ installation instructions. Connector test performance requirements are based upon no retightening. NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, does not call for retightening aluminum conductors. Connections should only be tightened if there is evidence of a loose connection. Both over-tightening and under-tightening can cause failure of aluminum or copper connections. Unwarranted re-tightening of screw-type connectors can lead to failure of the connection with either aluminum or copper conductors.
- See more at: http://www.aluminum.org/resources/electrical-faqs-and-handbooks/electrical#sthash.InhA6YOJ.dpuf
manwithtools
ALLIANCE MEMBER
Not all aluminum lugs have aluminum screws. Almost all neutral and ground bars in power panels are aluminum with zinc plated steel screws and accept wires in the 4-14 ga range. A fair number of connection and ground lugs are aluminum with steel screws as well. Larger sizes may have aluminium fasteners, but 4 ga and below frequently are zinc steel.
True. But steel screws are mainly only used in grounding applications, which do not see the same thermal cycling.
Regardless, these terminals were tested with the steel screw, others weren't. You should always use the same type of screw that was intended by the manufacturer.