torque on wires

Status
Not open for further replies.
W

wyboy

Senior Member
If wires have already been over tightened can they be re-terminated to a specific torque or does the old termination have to be cut off?
 
R

RICK NAPIER

Senior Member
Location
New Jersey
I would say the old termination should be cut off. By over tightening the wire may have been damaged or compressed to were the proper torque may not be sufficient.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
RICK NAPIER said:
I would say the old termination should be cut off. By over tightening the wire may have been damaged or compressed to were the proper torque may not be sufficient.
Click to expand...

I don't really think the issue is with the conductors.....

Over tightening may have cause the threads to yield. There is no repair for this, replacement only.

Yielding can be difficult to diagnose. It may manifest itself in the form of galling or flaking, but not always. If the yield remained in the ductile state, there may be no way other than precise thread measurements to make an accurate determination.
 
Jim W in Tampa

Jim W in Tampa

Senior Member
Location
Tampa Florida
K8MHZ said:
I don't really think the issue is with the conductors.....

Over tightening may have cause the threads to yield. There is no repair for this, replacement only.

Yielding can be difficult to diagnose. It may manifest itself in the form of galling or flaking, but not always. If the yield remained in the ductile state, there may be no way other than precise thread measurements to make an accurate determination.
Click to expand...

And the inspector will check for this how ?
 
R

rickgomes26

Member
That's a great question. One I had not long ago when I asked the electrician to show his lugs were torqued on some switch gear. He had the marks on the lugs indicating they had probably been there but I asked him to check anyway. He ended up being able to get quarter turns on several.

After that I questioned whether or not I should ask to witness torque testing as I was concerned about whether the conductors or the lug terminals might be damaged by this even if they're not tightened beyond their spec???
 
brian john

brian john

Senior Member
Location
Leesburg, VA
rickgomes26 said:
That's a great question. One I had not long ago when I asked the electrician to show his lugs were torqued on some switch gear. He had the marks on the lugs indicating they had probably been there but I asked him to check anyway. He ended up being able to get quarter turns on several.
Click to expand...

And you often will. Torque a conductor today and in a short time you can get movement from a torque wrench.

After that I questioned whether or not I should ask to witness torque testing as I was concerned about whether the conductors or the lug terminals might be damaged by this even if they're not tightened beyond their spec???
Click to expand...

While we torque everything (and I have since 1976), I would bet 80% of conductors are over tightened and 15% are below specified torque. Of the 5% that are torqued I bet less than 95% are with a calibrated torque wrench. So in my opinion your time is better spent than watching conductors being torqued.

Do you have all the specified torque values?
Do you inspect the torque wrench to verify the settings and calibration?
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
wptski said:
Never heard of Heli-Coil?
Click to expand...

I have used Heli-Coils many times. I have several kits in my tool box......for cars.

I don't know that I would trust them for electrical connections. Since it is guaranteed that the coil and the lug will not be of the same alloy, there is a risk of bi-metallic reactions. Also, there are now twice as many surfaces to oxidize.

I am curious if there are thread repair kits that are UL listed. I looked at a couple of my kits and did not see a UL listing.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Jim W in Tampa said:
And the inspector will check for this how ?
Click to expand...

That's all that matters?

Not to me. In fact, since damage from over tightening won't show up until disaster strikes makes the issue all the more important.

I have never done my job based upon what an inspector will likely notice and what they won't. I am my own worst (or best, depending upon your perspective) inspector.
 
K8MHZ

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
brian john said:
And you often will. Torque a conductor today and in a short time you can get movement from a torque wrench.



While we torque everything (and I have since 1976), I would bet 80% of conductors are over tightened and 15% are below specified torque. Of the 5% that are torqued I bet less than 95% are with a calibrated torque wrench. So in my opinion your time is better spent than watching conductors being torqued.

Do you have all the specified torque values?
Do you inspect the torque wrench to verify the settings and calibration?
Click to expand...

If the torque values were determined properly, they take into account the thermal cycling that will occur. The installation value will always be higher than the operating value. The trick is getting the specs so that when the connection relaxes over time, there is still a good connection. No matter how much torque is put on a terminal it will always be susceptible to thermal cycling.

(I spent a couple years in my former life as a metallurgical tech at a jet turbine engine parts manufacturer)

To check and re-torque or not should also be part of the design parameters, but we all know that if a tight connection somehow got loose, it won't get any tighter on it's own. Cinching it back down is prudent regardless of what the nomenclature indicates, unless the conductor is damaged, of course.

In the field I see many loose connections. I have never seen a failure due to an electrician tightening loose connections, just failures from people over tightening them or not tightening them enough.

Just some food for thought.....the torque values are calculated to put a certain amount of tensile force on the fastener. Some of that torque will be needed to overcome friction. Here is the question: Will cleaning and lubricating the threads (in order to minimize friction) affect the tensile force? I believe it does. I also believe that the torque specs are calculated with clean and lubricated fasteners and that using those specs on corroded and/or dirty fasteners will result in less tensile force being exerted on the fastener, and result in too loose of a connection.
 
R

rickgomes26

Member
It's still mind boggling to me how many "electricians" are out in the field practicing that don't own torque tools, wrenches, screwdrivers, etc. In commercial work its not AS bad, but in residential the overall quality is WAYYY down.

I've seen pics of what can happen when there are loose connections and since its something that easy enuf to prevent, albeit time consuming during an inspection, I check it.

I do receommend they wait till I get there to torque them but will ask to check even if they're already marked.

Thanks and sorry for potentially hijacking the thread
 
B

Bob Janice

New member
Aluminum Wire ,torque

Aluminum Wire ,torque

I am on the Board of directors of a Senior Mobile Home Park. We just had a three year preventive maintenance on all transformers, Breakers etc.. I asked one of the electricians what they torque the connectors at.. His answer got me thinking.. He advised " We tighten the connectors more than the torque calls for, this makes a better conection" By reading this forum I concider it to be a little dangerious.. The heat of the summer is coming and the transformers are out in the heat..
Am I wrong in thinking their procedure was incorrect?

FYI: The Electric in the Park is park owned, Meters Park read etc..

Your comments needed.

Thanks
 
brian john

brian john

Senior Member
Location
Leesburg, VA
rickgomes26 said:
It's still mind boggling to me how many "electricians" are out in the field practicing that don't own torque tools, wrenches, screwdrivers, etc. In commercial work it’s not AS bad, but in residential the overall quality is WAYYY down.
Click to expand...

Actually (I would think) it is a based on the fact that most circuits are not loaded above 80%-100%, and that is why we (as a trade) get away with a wide margin of error in torque values and connections. Torquing enforcement is a recent issue, and we have been installing electrical systems for a long time.

I've seen pics of what can happen when there are loose connections and since its something that easy enuf to prevent, albeit time consuming during an inspection, I check it.
Click to expand...

In my experience most loose connections are due to OPPS I missed that one, not a lack of force by the installer, and the remaining connections that are not torqued to the proper value are generally over tightened. Get a wrench and 2' of 1" EMT and that is the philosophy many electricians use.


I do recommend they wait till I get there to torque them but will ask to check even if they're already marked.
Click to expand...

If it is over tightened how do you know? The torque wrench will click before you reach the value.
What do you do for large projects? Like the one we just tested 100's of terminations all made on a Sunday?


Just my opinion, but if you cannot put faith in them to do this simple task then they HAVE NO BUSINESS in the trade. There are either good or not, and if they lie about this, there are bigger issues you need to be concerned about.

Thanks and sorry for potentially hijacking the thread
Click to expand...
 
Last edited:
E

elohr46

Senior Member
Location
square one
K8MHZ said:
If the torque values were determined properly, they take into account the thermal cycling that will occur. The installation value will always be higher than the operating value. The trick is getting the specs so that when the connection relaxes over time, there is still a good connection. No matter how much torque is put on a terminal it will always be susceptible to thermal cycling.

(I spent a couple years in my former life as a metallurgical tech at a jet turbine engine parts manufacturer)

To check and re-torque or not should also be part of the design parameters, but we all know that if a tight connection somehow got loose, it won't get any tighter on it's own. Cinching it back down is prudent regardless of what the nomenclature indicates, unless the conductor is damaged, of course.

In the field I see many loose connections. I have never seen a failure due to an electrician tightening loose connections, just failures from people over tightening them or not tightening them enough.

Just some food for thought.....the torque values are calculated to put a certain amount of tensile force on the fastener. Some of that torque will be needed to overcome friction. Here is the question: Will cleaning and lubricating the threads (in order to minimize friction) affect the tensile force? I believe it does. I also believe that the torque specs are calculated with clean and lubricated fasteners and that using those specs on corroded and/or dirty fasteners will result in less tensile force being exerted on the fastener, and result in too loose of a connection.
Click to expand...

Thanks for the very informative post. I've often wondered to myself as I was torqueing down conductors what the actual value was in doing this 'cause as you have stated we (electricians) all know that terminations will loosen from time to time and need to be retightened. I can see using a torque wrench on bolted buss bars, but on conductors it just seems fruitless with the exception being mac-adapts.
 
Last edited:
Status
Not open for further replies.
Top