ECN Forum Forums Code Related Discussion NEC & other Code issues Torque Requirements

http://www.necdirect.org/pdfs/A110.pdf
log# 2048, pg 4

i really can't take this seriously

Tom,
Even if the connection has not been energized, you will find that the head will turn before you reach the specified torque. This is because there is some "cold flow" of the conductor bewtween the time it is installed and when you test it.
Don(resqcapt19)

Sounds to me that there should be a rate-of-time factor involved... if you torque it down (hypothetically) with a pneumatic tool, or very slowly with a torque wrench, that the integrity would be compromised between the two extremes of speed due to friction / temperatures affecting the calculations that the manufacturer's used to get their numbers. (Whew!)

Any comments?

Just how exact of a science does this have to be?

Sparky,
If this isn't already covered by 110-3(b), I think it should be.
Hey, does anybody put Noalox on the lug's screws to stop that squeaky-squeak,jerky-jerk? I do, and I think I get a closer value by doing so.




[This message has been edited by electure (edited 07-11-2001).]

electure;
well.... believe it or not, No-Lox is a listing requirement of some service equipment.

and the tourqe thing, the intention is good, don't get me wrong. it's just that there are a multitute of variables here that a torque wrench will not address, so to me it's a very generic 'fix' . As Virgil and Don's posts eludes to, the physical characteristic's involved are fairly deep. My point of view is tainted by having to work with engineers for a decade who would probably have a 3 day pow-wow resulting in a mini-series , such is mil-spec!

In the practical world , think of all the torque requirements that could apply here, as we seem focused only on service gear;
-every switch...
-every receptacle...
-every wirenut...
-every pipe fitting...
-every lug, bug...
no one , other than an extreem obsessive/compulsive individual is going to actually use a tourqe indicating tool on all of this

yesterday's observation;
Siemens now makes a 'speed-screw' panel. This has Grn/Noodle bars with combo square drive heads. The installer can now use a bat-drill to drive all these home, it really works well, and as i was doing so i wondered if the clutch settings could be translated into inch-pounds

And to add, how large of a window is the margin of error?

Does 250 in-lbs torque mean not 249.9999999 and not 250.0000001, but 250.00000000 ????


Clutch settings torque... Great idea!

[This message has been edited by sparky66wv (edited 07-12-2001).]

Hello Bob: I am in Kansas and one of your former grounding students Dan Deneault was trying to remember your method of checking the torque at termination's? Can you help here?

Joe

Answer: Well Joe ... as an inspector you'll want to see if the torque requirements have been met. What I do is set my calibrated torque wrench at 15% below the torque setting used by the installer. If I get movement then it's a failed connection that requires correction. This way I'm not altering the installation.

Once the installer knows you will be checking then, as if by magic, this torque requirements are met.

Is funny how this happens on a job.

Say HI to Dan ... Bob N

>Clutch settings torque...
They do represent torque. But they vary from machine to machine. You can use your torque wrench to find out what setting slips the clutch. It might be 9 on one tool and 18 on another for about the same inch-lb torque.


Too bad the drill manufacturers don't just calibrate the clutch in recognizable and standard units right from the factory.

>how large of a window is the margin of error?
I would say at least 10%. 250 is 225 to 275.

But if the inspector is checking, I would say 250 means 250 to 275.

Virgil,

One of my torque wrenches is from Sears, goes to 250 lb/inches and I think it was under $50.

Tom