# torque



## french connection!! (Dec 13, 2007)

we have to torque all the terminals connections to manufacture specification here in electric panel for inspection , and I'd like to know how many of you have the same requirement , which I think it's not a bad idea . I usually also check if everything is tied when I open a new panel . I remember torquing everything when I worked in industrial and even in some occasion had to do some check every 6 months on some equipment .


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## crosport (Apr 4, 2010)

My wrist is my torque wrench.Never torqued connections,always just made tight as possible.Grabbing conducter and moving it back and forth a little and then re-tightening has always worked for me.


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## 360max (Jun 10, 2011)

crosport said:


> My wrist is my torque wrench.Never torqued connections,always *just made tight as possible*.Grabbing conducter and moving it back and forth a little and then re-tightening has always worked for me.


..for starters you are probable over tightening, secondly, it is not a code compliant install if you where to go by the book.


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## erics37 (May 7, 2009)

crosport said:


> My wrist is my torque wrench.Never torqued connections,always just made tight as possible.Grabbing conducter and moving it back and forth a little and then re-tightening has always worked for me.


I do that a lot too for little crap, but on bigger breakers or terminal points I always use a torque wrench. You're over-tightening your stuff.

Read this article:

Don't Be Uptight: Tightening connections to the proper torque


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## chicken steve (Mar 22, 2011)

UL 486A-B Recommended tightening tourqe, is now in Informational annex I

~CS~


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## stuiec (Sep 25, 2010)

erics37 said:


> I do that a lot too for little crap, but on bigger breakers or terminal points I always use a torque wrench. You're over-tightening your stuff.
> 
> Read this article:
> 
> Don't Be Uptight: Tightening connections to the proper torque


 
not being a wise-ass, just don't know...what is the downside of overtightening? (didn't see a why/how in the article)


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## JPRO2 (Dec 17, 2008)

It could become a hot spot if you start to damage the wire


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## erics37 (May 7, 2009)

stuiec said:


> not being a wise-ass, just don't know...what is the downside of overtightening? (didn't see a why/how in the article)


Damage the lug, damage the conductor, break strands, etc.

Here's another article (a bit more comprehensive):

Do You Have a Calibrated Arm?


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## stuiec (Sep 25, 2010)

Okay, so when I am landing a #3 in a lug, I was taught to tighten, wiggle, tighten, wiggle, tighten. If I use my torqe wrench (an ordinary torque wrench will do?), is the procedure the same?


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## niteshift (Nov 21, 2007)

360max said:


> ..for starters you are probable over tightening, secondly, it is not a code compliant install if you where to go by the book.


Yep. I find way more stuff over tightened, then are loose. Some people make a little too sure thier connections are tight.
Torque wrenches also need certification to be deemed accurate. Yearly?

When tightening with torque wrench, if you never used one, most would be surprized where a bolted connection is tight according to spec, compared to how tight they would've made it with a standard wrench.


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## CADPoint (Jul 5, 2007)

Most modern Cans/Panels come with a sticker that's will state the torque requirements.


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## tkb (Jan 21, 2009)

chicken steve said:


> UL 486A-B Recommended tightening tourqe, is now in Informational annex I
> 
> ~CS~


What is the significance of columns A or B?
It is not clear as to which column to use.


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## micromind (Aug 11, 2007)

stuiec said:


> not being a wise-ass, just don't know...what is the downside of overtightening? (didn't see a why/how in the article)


One disadvantage to overtightening bolted connections on switchgear busbars is that the mechanical stresses of a high current fault could easily break the bolts, thus releasing busbars into other busbars. 

BIG bang.......


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## hardworkingstiff (Jan 22, 2007)

erics37 said:


> Damage the lug, damage the conductor, break strands, etc.
> 
> Here's another article (a bit more comprehensive):
> 
> Do You Have a Calibrated Arm?


I think the last paragraph of that article says it all.


> So why don’t we have more failed connections if most electricians appear to be doing such a poor job of tightening them? The fact is that our electrical system has built-in safety factors, and circuits are rarely fully loaded. Lightly loaded circuits put less stress on weak connections, so they may perform satisfactorily for many years before experiencing a problem, if ever. However, this is no justification to ignore basic installation instructions. The bottom line is a torque wrench is an easy and inexpensive way to improve the reliability and safety of an electrical system.


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## Podagrower (Mar 16, 2008)

This issue requires a huge amount of retraining. The inspectors around here check for torque by trying to move the wires. If they move, they aren't tight enough. When lugs are torqued to factory spec, wires can often be moved. 30 lb-ft aint that tight.


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## Big John (May 23, 2010)

stuiec said:


> not being a wise-ass, just don't know...what is the downside of overtightening...?


 Here's my understanding: A conductor has a certain amount of elasticity: It will expand and contract based on temperature and pressure. If you put too much pressure on it with a lug, you permanently deform it, changing how it expands and contracts. Then when temperature changes cause the lug to change shape, the conductor no longer follows it and you get less surface contact, and a poorer connection. (Torque specs take this deformation into account, to answer your second question, this is why you never re-torque lugs, because you're applying more pressure than the specs intended.)

On lightly loaded circuits, this is less of a problem. On copper circuits this is less of a problem, because copper changes less with temperature than aluminum.

But in heavily loaded systems, this becomes very critical: A poor connection generates heat, the heat causes additional thermal expansion, which can worsen the poor connection, which causes more heat. It's self propagating. 

-John


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## J. Temple (Dec 30, 2011)

We started torquing all our panel connections a couple of years ago. Torque wrenches with allen sockets for most large lugs and adjustable torque limiting screwdrivers for most circuit breakers, neutral and ground bars. Even when the inspector does ask about torquing, we tell them we did and the rest of the inspection goes really easy.


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## nitro71 (Sep 17, 2009)

Never used a torque wrench.. Probably should but reality is that companies don't give a crap and don't want to provide you with the proper tools or give you the time to do the job correctly. Customer gets who they hire and what they pay for.


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## Semi-Ret Electrician (Nov 10, 2011)

stuiec said:


> not being a wise-ass, just don't know...what is the downside of overtightening? (didn't see a why/how in the article)


The POCO started providing crappy meter bases around here. Unless you used a torque wrench, they would break..usually on the last wire.


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## stuiec (Sep 25, 2010)

I want to get clear on this part. When I have landed a larger stranded consuctor, say # 6 and up, I have tightened the lug, and then worked the conductor back and forth so that the strands spread out, and then re-tightened. Is the proper procedure to torque to spec and leave it, without working the wire back and forth?


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## RGH (Sep 12, 2011)

My first 11 yrs in trade worked for military defense contractor..we built container units for the military....alsort things in them...we had specs on every damn thing that went into them....and we torqued every damn thing in them..the inspectors would check everything!!!! we had crimp compression specs aswell...they would take apart random connections and pull them apart with a stresser..unreal...zero tolerance for errors...tough work. welds were put on shake table till they failed...salt water test..heat test...altatude test....cold test..crazy..but it was for our military..nothing but the best for our boys:thumbsup: and as a side note they spec'd square d.


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## chicken steve (Mar 22, 2011)

tkb said:


> What is the significance of columns A or B?
> It is not clear as to which column to use.


i could use a little help there as well tkb ~CS~


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## hardworkingstiff (Jan 22, 2007)

stuiec said:


> I want to get clear on this part. When I have landed a larger stranded consuctor, say # 6 and up, I have tightened the lug, and then worked the conductor back and forth so that the strands spread out, and then re-tightened. Is the proper procedure to torque to spec and leave it, without working the wire back and forth?


I asked SQ D once about the "wiggling" of the wire while torquing. There answer was they do not spec how to do this, but in their opinion it was a good practice.

I always "wiggle" the conductor/s after torquing, then torque again (repeat until torquing is not required after a wiggle), not exceeding the recommended torque setting. IMO, it gets the air gaps out of the wire so you get a more solid connection. Now, I'm not talking about trying to break the wire off wiggle, just enough to get the air gaps out.


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## brian john (Mar 11, 2007)

crosport said:


> My wrist is my torque wrench.Never torqued connections,always just made tight as possible.Grabbing conducter and moving it back and forth a little and then re-tightening has always worked for me.


 
Which is exactly the issue, OVER TIGHTENING can be as detrimental as leaving them loose. Very few electrician intentional leave a loose connection. But a butt load of electricians way over tightening connections, deforming the connector, deforming the conductor and damaging the hard ware (stressing the hardware).

If anything firm snug. NOT jerk wad tight.


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## drsparky (Nov 13, 2008)

We always tourqued then marked each bolt with a slash. It helps you know that it was done and if anyone moved it later.


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## RGH (Sep 12, 2011)

tkb said:


> What is the significance of columns A or B?
> It is not clear as to which column to use.


I am not getting the column to use either...is it min/max column width?...then use table per slot size?...i can't find anything in 2011 to ref this....:blink: a vs b issue...perplexed...


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## tkb (Jan 21, 2009)

I usually wiggle the wire as I tighten to settle the strands and get a better connection at the final torque.


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## Shanaynay (Sep 4, 2021)

Big John said:


> Here's my understanding: A conductor has a certain amount of elasticity: It will expand and contract based on temperature and pressure. If you put too much pressure on it with a lug, you permanently deform it, changing how it expands and contracts. Then when temperature changes cause the lug to change shape, the conductor no longer follows it and you get less surface contact, and a poorer connection. (Torque specs take this deformation into account, to answer your second question, this is why you never re-torque lugs, because you're applying more pressure than the specs intended.)
> 
> On lightly loaded circuits, this is less of a problem. On copper circuits this is less of a problem, because copper changes less with temperature than aluminum.
> 
> ...


asking as a first year, ive just started landing the SC into panels for apartments we are currently roughing in. i've never done this before so i assumed to tighten the lugs until the cable cannot wiggle loose, the cables are aluminum and after tightening they were slightly flattened, will this cause any complications once power is supplied to the breaker panel? dont wanna be the one responsible for a big bang and a rework, wasnt aware of torque specs until after the work was done.


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## MikeFL (Apr 16, 2016)

Shanaynay said:


> asking as a first year, ive just started landing the SC into panels for apartments we are currently roughing in. i've never done this before so i assumed to tighten the lugs until the cable cannot wiggle loose, the cables are aluminum and after tightening they were slightly flattened, will this cause any complications once power is supplied to the breaker panel? dont wanna be the one responsible for a big bang and a rework, wasnt aware of torque specs until after the work was done.


You should be asking your journeyman. As a first year you have to be working under somebody.


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