# Wire Terminations



## joesparky28 (Mar 12, 2015)

I have read in the code in the past that a conductor is only allowed to be terminated once. If you have to remove it from the breaker, before you can re-terminate it, you must cut the part off that was terminated, and start with new end. Have any of you heard of this? I tried to find it in the code but cant locate it. Does anyone know where I could find this in the code?


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## Majewski (Jan 8, 2016)

joesparky28 said:


> I have read in the code in the past that a conductor is only allowed to be terminated once. If you have to remove it from the breaker, before you can re-terminate it, you must cut the part off that was terminated, and start with new end. Have any of you heard of this? I tried to find it in the code but cant locate it. Does anyone know where I could find this in the code?


how do you expect to torque something again without severing the damaged/used conductor?


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## joesparky28 (Mar 12, 2015)

I was just looking for the code reference that requires each termination to be torqued only once. I am trying to find the code article for an apprentice. He was expecting that you could just re-torque a wire that had already been torqued once. But doing so is a code violation.


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## Majewski (Jan 8, 2016)

joesparky28 said:


> I was just looking for the code reference that requires each termination to be torqued only once. I am trying to find the code article for an apprentice. He was expecting that you could just re-torque a wire that had already been torqued once. But doing so is a code violation.


how exactly do you re torque something?


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## MotoGP1199 (Aug 11, 2014)

90% of the original value to check torque is the best you can do


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## Majewski (Jan 8, 2016)

MotoGP1199 said:


> 90% of the original value to check torque is the best you can do


you either torque it or redo it new.... not inbetween.


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## MotoGP1199 (Aug 11, 2014)

Majewski said:


> you either torque it or redo it new.... not inbetween.


That is the UL508a approved method to check torque


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## Majewski (Jan 8, 2016)

MotoGP1199 said:


> That is the UL508a approved method to check torque


dont u talk to me in that tone of type


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## paulengr (Oct 8, 2017)

joesparky28 said:


> I have read in the code in the past that a conductor is only allowed to be terminated once. If you have to remove it from the breaker, before you can re-terminate it, you must cut the part off that was terminated, and start with new end. Have any of you heard of this? I tried to find it in the code but cant locate it. Does anyone know where I could find this in the code?


It is not In any Code except that you are supposed to follow directions. When you place a conductor into a mechanical connector it deforms the copper and forms effectively a cold welded joint. This is supposed to be a one time process. Read the technical data from Burndy, etc.

But this is similar to reusing fasteners. The threads in a nut are permanently deformed if you torque to specification. It’s common knowledge that you are supposed to replace nuts and bolts if you take something apart. Obviously though we can’t realistically do that with terminals that are built into a lot of electrical equipment. At best a crimped lug and bolting jf (with new bolts and nuts??) is the closest that is even possible,

A similar problem exists in that every torque spec out there for electrical including NEC gives a single number. It doesn’t say minimum, maximum, or give an error (+/- range). So if it says 50 foot pounds is it faulty to tighten to 51? What if it’s only 49? Mechanical torque specs give ranges for a reason.

Realistically our mechanical counterparts are way ahead of us on fasteners. Fortunately the acceptable torque is a very wide range.


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## Majewski (Jan 8, 2016)

paulengr said:


> It is not In any Code except that you are supposed to follow directions. When you place a conductor into a mechanical connector it deforms the copper and forms effectively a cold welded joint. This is supposed to be a one time process. Read the technical data from Burndy, etc.
> 
> But this is similar to reusing fasteners. The threads in a nut are permanently deformed if you torque to specification. It’s common knowledge that you are supposed to replace nuts and bolts if you take something apart. Obviously though we can’t realistically do that with terminals that are built into a lot of electrical equipment. At best a crimped lug and bolting jf (with new bolts and nuts??) is the closest that is even possible,
> 
> ...


there IS one code very much about this and its 110.3b


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## mburtis (Sep 1, 2018)

paulengr said:


> It is not In any Code except that you are supposed to follow directions. When you place a conductor into a mechanical connector it deforms the copper and forms effectively a cold welded joint. This is supposed to be a one time process. Read the technical data from Burndy, etc.
> 
> But this is similar to reusing fasteners. The threads in a nut are permanently deformed if you torque to specification. It’s common knowledge that you are supposed to replace nuts and bolts if you take something apart. Obviously though we can’t realistically do that with terminals that are built into a lot of electrical equipment. At best a crimped lug and bolting jf (with new bolts and nuts??) is the closest that is even possible,
> 
> ...


Maybe this is true for some or all electrical equipment I don't know. However back when I was designing mechanical equipment we used non failure type torque specs. Traditional engineering says that if a bolt is tightened to 60 percent of its yield strength it won't come loose, typically most torque specs are based on 75 percent yield strength, sometimes 90 percent. Now correlating torque to bolt tension is an educated hope and a poke, hence the large ranges of acceptable torque. These types of connections it is assumed that the fasteners can be reused over and over again. I would assume most electrical equipment is designed to these torque values but I really have no idea. Now a lot of modern engineering takes advantage of strain hardening ect to obtain high torque values out of small bolts by torqueing them past the yield point in which case the bolts have actually elongated and can't be reused, cylinder head bolts on most cars since the 90s are an example. What the engineers at sqaure d or Eaton do for electrical equipment I have no idea.


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## u2slow (Jan 2, 2014)

Serious question.... How does one do prescribed preventative maintenance on tightening wire terminals/lugs if they are not to be re-tightened without cutting a fresh end? Most wire would be too short after several months of 'checks'.

Not everybody works on new installs and walks away.


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## Majewski (Jan 8, 2016)

u2slow said:


> Serious question.... How does one do prescribed preventative maintenance on tightening wire terminals/lugs if they are not to be re-tightened without cutting a fresh end? Most wire would be too short after several months of 'checks'.
> 
> Not everybody works on new installs and walks away.


serious?


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## 205490 (Jun 23, 2020)

Service loops are great, ironically when doing service work they're not always there.
Old solid core wire is a pita, and of course whatever is down needs to be up & working NOW.


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## u2slow (Jan 2, 2014)

Majewski said:


> serious?


Only a little... I know what_ I _do....


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## Wirenuting (Sep 12, 2010)

Ok so you land a wire into the main lug. 
You torque it down to specs.

Do you wiggle it once, twice, and re-torque it?
Or do you stop at that first time?


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## Forge Boyz (Nov 7, 2014)

Wirenuting said:


> Ok so you land a wire into the main lug.
> You torque it down to specs.
> 
> Do you wiggle it once, twice, and re-torque it?
> Or do you stop at that first time?


I tried not wiggling the wires once upon a time. The inspector grabbed ahold of them and told me they were too loose. Ever since then I tighten, wiggle, and retighten until it stops loosening up. At that point I consider it torqued. 

Sent from my SM-G970U using Tapatalk


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## Wirenuting (Sep 12, 2010)

Forge Boyz said:


> I tried not wiggling the wires once upon a time. The inspector grabbed ahold of them and told me they were too loose. Ever since then I tighten, wiggle, and retighten until it stops loosening up. At that point I consider it torqued.
> 
> Sent from my SM-G970U using Tapatalk


Same here, but have we been doing it correctly the last 40 years? I don’t know. 
But it is nice to see the same gear I installed many years ago still charging down the road.


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## CAUSA (Apr 3, 2013)

I find temperature has a lot to contribute to the torque as well.

when done in the cold you need to exercise the torque wrench on a test bolt to warm up the internal shaft to get a good reading. And re test the torque after a few minutes. Have found that material relaxing and bolt stretch on buss is the worst. But a conical washer helps.

Calibrating the wrench helps as well. Because how do you really know the settings are correct. The tools been kicking areound the truck box in all temperature swings and you finally go to use it, can it be trusted.

I will admit that I only cut and re-land aluminum. For copper if it is in the #2 and larger It gets cleaned and back it goes.


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## backstay (Feb 3, 2011)

When terminating the bottom lugs on a meter, have you ever broke the lug mounts? Asking for a friend.


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## wiz1997 (Mar 30, 2021)

backstay said:


> When terminating the bottom lugs on a meter, have you ever broke the lug mounts? Asking for a friend.


Yes.


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## backstay (Feb 3, 2011)

wiz1997 said:


> Yes.


The power company gets really pissed…I heard, twice. 😳


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## Majewski (Jan 8, 2016)

backstay said:


> The power company gets really pissed…I heard, twice. 😳


last one time the lineman did it to me and just walked away......energized and left. good times


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## wiz1997 (Mar 30, 2021)

I have worked in places where if the wire was removed after the first torque it had to be cut back, stripped inserted in the terminal block and then re-torqued.

One was the South Texas Nuclear Project, the other was when working on DCS cabinets in oil refineries and chemical plants.

No code requirement, but usually a SOP (standard operating procedure) requirement by the Electrical engineer.

These requirements where typically aimed at small solid wires used on control wiring.

Would sit for days,weeks even months terminating 300 pair cables in DCS cabinets or at the other end in very large junction boxes.

I have seen wires pinched in two at the terminal block by maintenance preforming 
the quarterly or yearly PM checks on control panels.

Many times the wire will be pinched in two but touching just enough to make the circuit until a vibration or temperature change separates the wire.

Chased an every now and then E-stop circuit for days until we figured out the PM was done just prior.

Now if I reterminate a wire it gets a good tug.


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## gpop (May 14, 2018)

u2slow said:


> Serious question.... How does one do prescribed preventative maintenance on tightening wire terminals/lugs if they are not to be re-tightened without cutting a fresh end? Most wire would be too short after several months of 'checks'.
> 
> Not everybody works on new installs and walks away.


Use a thermal camera its quicker, Doesn't require the panel to be down and lets face it if it ain't hot its tight enough.


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## Majewski (Jan 8, 2016)

gpop said:


> Use a thermal camera its quicker, Doesn't require the panel to be down and lets face it if it ain't hot its tight enough.


Not unless youre certified


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## gpop (May 14, 2018)

Majewski said:


> Not unless youre certified



you don't have to be certified to be a electrician why would you need one to use a camera.


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## Majewski (Jan 8, 2016)

gpop said:


> you don't have to be certified to be a electrician why would you need one to use a camera.


oh idk.. i read it on a bathroom wall somewhere


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## u2slow (Jan 2, 2014)

gpop said:


> Use a thermal camera its quicker, Doesn't require the panel to be down and lets face it if it ain't hot its tight enough.


We do that for panels, annually, but aren't always checking at the time of peak loading. I'm a little miffed at Fluke that they want a subscription for their Connect software. 

Two pieces of equipment I'm thinking of have banks of heating elements that cut in and out on-demand. It's more sensible to shut the thing down and torque. Monthly routine. Copper. I'm not cutting the wires shorter.


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## gpop (May 14, 2018)

u2slow said:


> We do that for panels, annually, but aren't always checking at the time of peak loading. I'm a little miffed at Fluke that they want a subscription for their Connect software.
> 
> Two pieces of equipment I'm thinking of have banks of heating elements that cut in and out on-demand. It's more sensible to shut the thing down and torque. Monthly routine. Copper. I'm not cutting the wires shorter.


We did the thermal scan of over 600 motor buckets every month then checked every connection / breaker / contactor once a year while also inspecting every disconnect and pecker head. We reduced our breakdowns from hours per week to hours per year. Really boring after the first 3 years as we might go months and find nothing of even minor interest.


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## u2slow (Jan 2, 2014)

That's a huge plant @gpop !


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## splatz (May 23, 2015)

u2slow said:


> Serious question.... How does one do prescribed preventative maintenance on tightening wire terminals/lugs if they are not to be re-tightened without cutting a fresh end? Most wire would be too short after several months of 'checks'.
> 
> Not everybody works on new installs and walks away.


Inspection / PM for torque is a tricky thing. Setting the torque wrench to the specified torque and re-torquing is not recommended, the torque specification is supposed to be such that it is hit once and done. Re-applying the same torque repeatedly will result in over-torquing the fastener. However I have heard of setting the torque wrench to 90% and hitting the fastener as a test, if it moves, it fails. However if it fails, it's not acceptable to set the wrench to 100% and hit it again to bring it to specified torque, that would count as re-torquing which is a no-no. I guess you're supposed to trim it and re-terminate if it fails. Of course I could totally see this procedure leading to every conductor failing every month. 

Even though it's not proper, as mentined in other posts, lots of times if you don't break the rules and re-torque at installation, it won't even pass a tug test at inspection time, which creates a situation where you are going to break a rule one way or the other and most would agree common sense is that re-torquing and passing the tug test is the lesser evil.


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## Almost Retired (Sep 14, 2021)

backstay said:


> When terminating the bottom lugs on a meter, have you ever broke the lug mounts? Asking for a friend.


yep. and i kept those spare parts from repairing it. also kept other spare parts from upgrades. It happens occasionally, not very often


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## u2slow (Jan 2, 2014)

splatz said:


> Inspection / PM for torque is a tricky thing.
> ...
> Of course I could totally see this procedure leading to every conductor failing every month.


Our engineering directives come down from many payscales above mine. They insist on 'tightening up' connections on monthly intervals. We don't follow NEC or CEC, but rather the TP127E document which is brief by comparison, and defers to IEEE standards frequently.

I dug into one mfr's equipment manual:

"Main supply lugs should be tightened every 24 hours during the first week of operation. After the first week, the main supply lugs should be tightened every 30 days. After 30 days of operation, all electrical power connections should be tightened (with power off)."

"Tighten all the electrical connections that could have loosened due to heat expansion and contraction. Pay particular attention to the main lugs that receive the power circuit."

Another section lists the in-lb torque spec for the larger conductors and general statement about torqueing to recommended/labelled torque values for lesser wire sizes. No mention of wire ends needing to be fresh each time.

Keep in mind that inspections on a ship aren't the same as ashore. The authority who normally attends annually is checking a handful of safety systems across the entire ship over a few days - not nitpicking electrical panels. (They do expect a thermal scan report for panels). There's a regulatory expectation we follow our own, vetted, in-house procedures. I can weigh in with opinions on the procedures, but I can't change them myself. We are not experiencing termination failures in the 3 years the vessel has been in service.


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## joe-nwt (Mar 28, 2019)

u2slow said:


> "Tighten all the electrical connections that could have loosened due to heat expansion and contraction. Pay particular attention to the main lugs that receive the power circuit."


Ya know, when I read things like that, "buck passing" springs to mind.


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## mburtis (Sep 1, 2018)

From my stand point of being in house maintenance I've went back and forth on the whole intrusive PM type work. By that I mean altering a system that is working by doing something to it because a book tells you that you should. Kinda like disconnecting a motor or transformer once a year to meg it, is the value of the data collected worth the risk your taking in breaking a proven good connection ( what's the risk of making a bad termination on hook up, or damaging the conductors, etc.) This comes down to equipment criticality and history for me. Personally for my plants ive decided that I'm not going to go around disturbing running systems, but I will do various inspections/tests that I can perform without making changes to the system. As far as termination torque it seems like taking a gander with the flir every so often offers the best chance of finding issues without disturbing a known good system. However there are some caveats, such as to be worth anything the system has to be under load, which means exposing everything while energized. Also some training is needed to analyze what your seeing and how to use the equipment. Maybe I'm a simpleton but it seems like shutting down and doing a visual inspection and giving the wires the ole tug test could be as effective as anything while reducing the chance of messing with stuff for no reason. But what do I know, I for sure don't cut the wire off every time I lift it and reterminate it, so I must be hack. Back to the original question, I'm not aware of any code that requires you to trim a wire every time you lift it and reland it. Not saying it doesn't exist I've just never heard of it. If that was true though I don't know how it would work out for industrial equipment that gets changed out or rebuilt every couple years or every couple of weeks or every couple of days. Wires going to get awfully short in a hurry.


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## joe-nwt (Mar 28, 2019)

Predictive maintenance. Some organizations use it.


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## paulengr (Oct 8, 2017)

mburtis said:


> Maybe this is true for some or all electrical equipment I don't know. However back when I was designing mechanical equipment we used non failure type torque specs. Traditional engineering says that if a bolt is tightened to 60 percent of its yield strength it won't come loose, typically most torque specs are based on 75 percent yield strength, sometimes 90 percent. Now correlating torque to bolt tension is an educated hope and a poke, hence the large ranges of acceptable torque. These types of connections it is assumed that the fasteners can be reused over and over again. I would assume most electrical equipment is designed to these torque values but I really have no idea. Now a lot of modern engineering takes advantage of strain hardening ect to obtain high torque values out of small bolts by torqueing them past the yield point in which case the bolts have actually elongated and can't be reused, cylinder head bolts on most cars since the 90s are an example. What the engineers at sqaure d or Eaton do for electrical equipment I have no idea.


You CAN theoretically load past the yield point but as you do so the bolt is stretching including the threads. So the only way to do this is with a very special fastener. With just cap screws and nuts it just fails and there is no way to balance on the edge.



https://qph.fs.quoracdn.net/main-qimg-f626091a13fa042e1246b146d9f97b38



Those so called percentages of yield simply aren’t true. There is a value called the nut factor, typically 0.15-0.20, which is what is actually used. Along with it you will see a formula that says torque = Nut factor x tension x bolt diameter.

You can Google as much as you want on but factor and listen to all the theoretical engineering nonsense, like this one:





__





Fastener Torque | Engineering Library


This page provides the sections on proper bolt torque from NASA's




engineeringlibrary.org







https://www.hexagon.de/rs/engineering%20fundamentals.pdf



The theoretical book smart engineers THINK that this is how it’s done but all they did was take nut factor K and throw a bunch of theoretical numbers into an equation to attempt to explain it. Let’s see why. So torque is force times length or in our case bolt diameter. So other than conversion factors if most of the torque went into tightening the fastener nut factor would be say 0.6-0.9 like you suggested. But it’s not. It’s 0.15 to 0.20 with most charts using 0.18 or 0.185.

Second NOBODY actually calculates it. It is empirical, NOT theoretical, What happens in reality is that we put the bolt into a bolt tester. This machine very accurately measured the bolt length and the torque as it turns the nut. So we get our “yield curve”. You can read the torque off the chart. If we had previously done a tension test (pull the bolt apart) we “know” the tension at the yield point. So we can divide the torque by the bolt diameter and the yield tension to calculate the nut factor.

If some theoretical idiot claims otherwise then please explain why after centuries we have no wAy to determine friction theoretically? About 75% of the torque is thread friction. So everything is empirical, NOT theoretical.

As far as reuse, read this Fastenal article that makes it clear bolts are one thing but nuts shouldn’t be reused.






Reuse of Fasteners | Fastenal







www.fastenal.com





Or this one with actual data:



https://www.boltscience.com/pages/the-re-use-of-threaded-fasteners.pdf



The NASA fastener manual and SAE manuals say something similar but I can’t give links to those.

As I said this is all VERY settled science. We just don’t like the answers in electrical work so we just ignore it. There is somewhat good reason for this. When you squeeze a wire you crack the oxide layer and you get metal on metal contact in a very small number of spots at the joint called aloha spots. These are the ONLY actual conductors. Further pressure creates more aloha spots but almost smears and enlarged the first ones. These are all cold welds. When we remove the pressure though these welds stay intact until the joint almost falls apart. So once made electrical contact is maintained almost at the same condition as it was when first tightened. This is why despite the engineers freaking out about looseness electrical joints don’t tend to fail over time unless you “retorque” a fastener. Bolts will relax over time which is why torque checking doesn’t work (another example of why NETA is clueless). So if you “check” torque ALL fasteners will measure low. And if you “fix” it (retighten) you will overtighten, causing plastic deformation and eventual failure.

I spent 2 years doing this twice a month on a Saturday in overtime on a fluidized bed dryer because of my clueless boss. We tightened the same bolts over and over until they snapped off. Wash, rinse, repeat. The money was good but spending fine with my baby girls was better time spent.


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## joe-nwt (Mar 28, 2019)

Almost no auto parts come with new bolts.


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## mburtis (Sep 1, 2018)

Like you say the nut factor or friction factor of the threads make a huge difference in the relationship between bolt torque and bolt tension. As with most things there is some level of approximation and running the calculations based on empirical tabled friction factors etc was close enough for what we were doing which was building really big hydraulic cylinders. 

As far as electrical connections are concerned I would be surprised if fastener tension plays much of a part at all. I would guess that the designers set the torque value based on the contact pressure they want on the wire, and my gut feeling is this is accomplished at very low levels of fastener tension. I've never designed a terminal block so I don't really know and I'm not about to go reverse engineer one for the fun of it. 

Like I said unless a connection gives me reason to believe it needs tightened I'm just going to leave it alone.


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## micromind (Aug 11, 2007)

joe-nwt said:


> Almost no auto parts come with new bolts.


And like just about everyone else, I re-use the ones I took out. In my case, thousands of them over the last half-century.


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## WannabeTesla (Feb 24, 2020)

In wind, proper torque and nut/ bolt reuse was a frequent discussion. Unfortunately, none of us were properly educated. I do know that we were required to make a lot of in- field decisions based on our various experience levels. As far as i know, none of the blade nuts we removed, greased, and re-torqued has failed yet.



gpop said:


> you don't have to be certified to be a electrician why would you need one to use a camera.


I think, legally, "certification" is the difference between an electrician and an electrical worker/ technician/ etc... I'm sure all of us know many "uncertified" individuals whos ability exceeds certified individuals and vice-versa. Out here, at least, it's the difference between pulling permits, certifying load calculations... it's the difference between having an opinion on whether or not a building electrical system is safe and legal in order for sale, rental, etc, and certifying that the system is, in fact, safe and legal. 




u2slow said:


> Our engineering directives come down from many payscales above mine. They insist on 'tightening up' connections on monthly intervals. We don't follow NEC or CEC, but rather the TP127E document which is brief by comparison, and defers to IEEE standards frequently.
> 
> I dug into one mfr's equipment manual:
> 
> ...


This looks like pure butt-covering to me, except for the part about your practice. That seems sound and the results speak for themselves.



paulengr said:


> You CAN theoretically load past the yield point but as you do so the bolt is stretching including the threads. So the only way to do this is with a very special fastener. With just cap screws and nuts it just fails and there is no way to balance on the edge.
> 
> 
> 
> ...


Thanks for the great info. Per Yogi Berra: "In theory there's no difference between practice and theory, but in practice there is."
In the Mil we used to say if it ain't broke, pm it until it is broke.


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## micromind (Aug 11, 2007)

I don't even mess with these silly lugs anymore.....Cadweld all the way!


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## paulengr (Oct 8, 2017)

mburtis said:


> Like you say the nut factor or friction factor of the threads make a huge difference in the relationship between bolt torque and bolt tension. As with most things there is some level of approximation and running the calculations based on empirical tabled friction factors etc was close enough for what we were doing which was building really big hydraulic cylinders.
> 
> As far as electrical connections are concerned I would be surprised if fastener tension plays much of a part at all. I would guess that the designers set the torque value based on the contact pressure they want on the wire, and my gut feeling is this is accomplished at very low levels of fastener tension. I've never designed a terminal block so I don't really know and I'm not about to go reverse engineer one for the fun of it.
> 
> Like I said unless a connection gives me reason to believe it needs tightened I'm just going to leave it alone.


There is a well known good contact pressure that guarantees a fastener will work over its life. There are a couple really good books on contact pressure theory. Most of it covers sliding contacts (breakers, contactors) but it still applies. Then as long as you know contact area that gives you the force needed. If you look at crimp lugs they often come in 2 different bolt sizes for bolting smaller and larger lugs together. The minimum available bolt hole size gives you an idea of minimum contact pressure needed. It’s much easier to make it work in a fastener than in day a breaker or contactor where it has to close and open.


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## cutlerhammer (Aug 16, 2011)

Majewski said:


> there IS one code very much about this and its 110.3b


110.3B: Installation and Use. Equipment that is listed, labeled,or both shall be installed and used in accordance with any instructions included in the listing or labeling.

See why many electricians smoke weed?


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## danielplace1962 (Mar 24, 2014)

Load goes up heat goes up. Heat goes up and wire expands making it extremely tight and the setscrew gets imbedded further in the wire. Now load goes away and it all cools again and now the assembly is not tight. At some point if not retightened the wire is loose and then the resistance increases and the process gets supercharged as it overheats and burns up.

It can happen more quickly with aluminum as it expands much more than copper when hot as well as being much softer material.

This is why you retighten it before the resistance goes up.


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## bill39 (Sep 4, 2009)

After reading all of this torque talk I can’t help but think that we have begun to overthink things too much. Just spitballing here, but from a practical perspective should we only be concerned about precise torquing above a certain wire size or current rating?

How many things look good on paper or theory but not in practice?


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