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How does an inspector know if you torqued a termination to the proper amount when he makes an inspection?
George Little
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They don't know and I can not see anyway they could unless they stand there and watch me do it.
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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Method 1:
He marks the position of the fastener, and using the proper tool applies torque to the lower limit.
If the fastener moves, he fails the job.
Method 2:
He requires a special inspection at the time of the instalation.
Method 3:
He requires a fastener where the head breaks off at the proper torque.
As an engineer I would require #2 or #3 and so state on the plans and bid sheets.
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Method 3:
He requires a fastener where the head breaks off at the proper torque. I sure would be interested to see any panels, breakers or busbars equipped with the breakaway heads. ![[Linked Image]](https://www.electrical-contractor.net/ubb/wink.gif) I have only seen bus duct available with those fasteners. As far as the inspector operating a tool that will not happen in my area. They will not take on that responsibility and I do not blame them. Who would pay for repairs if something breaks. Or say the inspector was the last one to touch the terminal and 11 months later it fails for any reason. In MA we are required to provide a one year warranty. Who would be responsible?
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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If you try torquing down something that is already torqued you risk over torquing it, as in breaking it.
Around here, some inspectors dont care. Some want something in company letter head stating you torqued everything. Some want to watch you.
Lately I've started marking my initials, the amount I torqued it to and the date. Haven't had an inspector bring up torquing since.
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I've seen a technique used to mark properly torque fasteners, which is to torque the fastener and then use a sharpie to draw a line from the center of the fastener off to one side of the surrounding material.
I've heard that a clueful inspector will understand this, and recognize it as meaning that the electrician actually took the time to properly torque the fastener. Of course it doesn't actually say what torque values was used, and nothing prevents someone from simply marking any random fastener.
I like the approach of recording the torque value that dmattox suggests. This permits an inspector to double check which torque value was actually used, and is a pretty nifty workmanship detail.
-Jon
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I have never had the issue of proper torque come up; it seems to be a "detail for geeks", and some assure me that the worst that will happen is that the inspector will ask to see your torque wrench.
I don't understand the concern over re-torquing a fastener. If you have tightened it to, as, 14 lb-in, wouldn't applying 14 lb-in to it again have no affect? It's not like a hammer blow, after all.
If I did have a concern, or wish to verify the tightness of a fastener, it seems to me that the best way to do this is to see what it takes to loosen the fastener, then re-tighten it.
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As an inspector all I can say is you don't know. I do check that they at least have a torque wrench on the job. If they use it, and if they use it properly, it is the installers responsibility not the inspectors.
If it fails it goes against the installer not the inspector. There are torque requirements for screws. Have you ever seen an electrician use a torqueing screwdriver when installing a receptacle ?
As an inspector you have to trust the licensed electricians.
[This message has been edited by Alan Nadon (edited 06-19-2005).]
Alan--
If it was easy, anyone could do it.
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I don't understand the concern over re-torquing a fastener. If you have tightened it to, as, 14 lb-in, wouldn't applying 14 lb-in to it again have no affect? It has an effect, and I say this from experience not from reading it somewhere. Re-torque the lugs enough times and you will crush the conductors. IMO most all of us, when tightening lugs free hand go far above the specified torque. Try using a torque wrench and I think you will be surprised how quick you here it click. They say in what I have read that that over tightening causes the conductor to 'cold flow'. [This message has been edited by iwire (edited 06-19-2005).]
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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I don't understand the concern over re-torquing a fastener. If you have tightened it to, as, 14 lb-in, wouldn't applying 14 lb-in to it again have no affect? It's not like a hammer blow, after all. If you torque something down, then immediately try torquing it again you will move the lug/bolt more than when you first torqued it, often substantially if the torqued rating is low. Worst case is that you might strip out a lug, nothing worse than trying to loosen a stripped lug.
IMO most all of us, when tightening lugs free hand go far above the specified torque. Try using a torque wrench and I think you will be surprised how quick you here it click.
I'd agree with that. I was torquing down some bussing with a helper a couple weeks ago. He was working with one of our other foremen saying they were using a wrench with a breaker bar. He was shocked with how little pressure was actually needed when you torqued it to manufacture's specs.
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And then there is rest of the story that makes it even more interesting: 430.9(C) Torque Requirements. Control circuit devices with screw-type pressure terminals used with 14 AWG or smaller copper conductors shall be torqued to a minimum of 0.8 N•m (7 lb-in.) unless identified for a different torque value.
Joe Tedesco, NEC Consultant
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I will of course defer to those of you with actual experience. I will accept that reptetitive torquing does make a difference.
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Sometimes connections are to tight.
Example: The square bit screw drivers on #14 solid not good. I rechecked a helpers neutral connections at panel board. loosen a couple of connections and found the wire fattened, by the Torque of square pressure connectors. almost breaking the wire in half. My fought because I told him to make sure all connections are tight! Also tried a torque wrench on 200 amp meter can to specs.,heard a snap and broke the insulator
behind the jaws. the tool is now in the storage unit.
TomL.
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Should be:"found the wire flatten"
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Mark Heller
"Well - I oughta....." -Jackie Gleason
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Oh that is from an even more ridiculous tool: http://www.sheldonbrown.com/tork-grip.html Now Bob, I had to googgle "cold flow", as it did sound like something you would want in a connection...
Cold Flow
As compared to Creep, cold flow has no units of measure. The best description of cold flow relating to application within the electrical industry, is an excessively high rate of creep i.e. normal creep rate static load condition would be expressed in a fraction of an inch per inch of length. Cold flow, conversely if possible to measure it in definable terms, would be expressed in terms of inches of movement per inch of length. Cold flow then can be expressed as movement of appreciable magnitude occurring at a stress level in a very short length of time at an ambient temperature. Neither time or temperature are critical in assessing the effecting force of cold flow.
It is significant to realize that it is an absolute necessity to have cold flow of the conductor within a bolted connector to develop the desired low resistance contact, required for electrical/mechanical stability of the connection. So is it necessary to have cold flow of both the conductor and connector in the making of a compression connection. In these two instances a mechanical union of the two components is made by means of an externally applied force to assure both electrical and mechanical reliability. In the case of a soldered or welded connection this component union is made metallurgically. Further research on cold flow is that it is a metalurogical term for cold forming of metals. The way wire is flattened in a lug so to speak. I guess that as long as the cross-sectional area of the wire is unchanged, and there is contact equaling that dimension, you have a good connection. But if you have enough 'cold flow' to squeeze the metal out like tooth paste out of both sides of a lug, and reduce the cross-sectional area, you have over-torqued. [This message has been edited by e57 (edited 06-20-2005).]
Mark Heller
"Well - I oughta....." -Jackie Gleason
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If retorquing causes problems, I would suggest that the problmes are not solved by torquing once and going away.
I only work under 200amps and all in copper, and for that work the wrong torque will not cause any long term damage.
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I only work under 200amps and all in copper, and for that work the wrong torque will not cause any long term damage. Regardless of your opinion it is a code violation. Do you consider yourself a professional electrician or a handyman?
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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I only work under 200amps and all in copper, and for that work the wrong torque will not cause any long term damage Doing Infrared Testing I come across many copper connections under 200 amps that are overheating from torque problems. When the insulation is breaking away from the conductor don't you consider that long term damage? Also like iwire has stated it is a code violation. Al
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Here is a picture of a 200 amp connection that seems to have a problem. ![[Linked Image]](https://www.electrical-contractor.net/forum/iw/200ampburntconnection.JPG) capt al provided this picture maybe he can fill in the details. Bob
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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iwire & capt al ---
Because I have no knowledge as to how far outside specs (if any) others tighten their fittings, I will not address problems that others may have with circuits under 200amps.
I have given 3 methods of checking torque. I don't see you offering a method to check torque.
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I have given 3 methods of checking torque. I don't see you offering a method to check torque I have not offered one because there is no way to check torque short of being there while it is being done. Method 1:
He marks the position of the fastener, and using the proper tool applies torque to the lower limit.
If the fastener moves, he fails the job. This does not check torque, this only ensure torque has been reached, it does not tell us if torque has been exceeded. Method 2:
He requires a special inspection at the time of the installation. I agree with Method 2 Method 3:
He requires a fastener where the head breaks off at the proper torque. I agree this will work but the application is limited and it will be a problem if a you have disconnect and reconnect a conductor. [This message has been edited by iwire (edited 06-25-2005).]
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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Just ask "Can I see your torque wrench". If he can find it he probably used it. If it is buried "somewhere in the truck" or back at the shop he probably didn't ;-)
Greg Fretwell
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George, I wish I could follow your logic. First you say: I only work under 200amps and all in copper, and for that work the wrong torque will not cause any long term damage. I believe the picture iwire posted for me shows long term damage on phase "A" Maybe I'm wrong. I always thought the insulation splitting off a conductor due to overheating was a bad thing. This connection was out of torque. According to you wrong torque is no problem. Look at the picture again if you want to continue believing torque is not an issue under 200 amps on copper conductors. The picture shows a 480 volt 100 amp disconnect switch for the emergency smoke exhaust fans in a warehouse. The only time these fans have ever ran was when maintenance tested the system quarterly. The fans do not have much run time so you can see what an under torqued connection can due in a sort period of time. Second: Because I have no knowledge as to how far outside specs (if any) others tighten their fittings, I will not address problems that others may have with circuits under 200amps. Lets forget the "others". Do you torque? As you can see from the posted picture torque does matter under 200 amps! Third: I have given 3 methods of checking torque. I don't see you offering a method to check torque. How about Infrared Testing your connections after installation. This is not a cheap way to verify torque. I have done this for an EC because in was in the specs for the job. He would get no final payment unless an IR report was submitted. Al [This message has been edited by capt al (edited 06-26-2005).]
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OK, I'm in on this one.....
Heads breaking off when torqued properly?
How do you get them off, if the heads break?
I mostly use crimps on anything over 8Awg stranded, no problems with torque and or conductor damage.
George, you as an engineer should already spec out the use of crimp connectors, the use of mechanical lugs should not be used IMO.
No having said that, when using solid conductors in say a resi panel, I doubt there is too much damage to soild conductors as one might expect. But I am sure it happens, when you tighten it like a gorilla.
"Tight is right", loose connections make heat and arcing.
Just my thoughts...
Dnk..........
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Heads breaking off when torqued properly?
How do you get them off, if the heads break? They are double headed bolts with a machined area between the two head that is designed to twist off at the required torque. They also make hex keys that work the same way. They are a "one time" torque tool. You insert the tool in the hex socket on the lug and use a socket wrench on the other end of the tool. It snaps at the correct torque. Don [This message has been edited by resqcapt19 (edited 06-26-2005).]
Don(resqcapt19)
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I don't know about the rest of you but my torque ratchet handle and my torque screwdriver are made to "break away" when you reach the preset torque value. I have seen and used torque wrenches that "click" when you hit the setpoint but allow further tightening beyond the "click". My tools will not allow you to go beyond their setpoint. I can use them to see if a value has been reached but I cannot tell if the value has been exceeded.
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capt al ---
I am sorry. I was too brief. I only work on systems under 200amp and 240volt. (I would not have enough work at higher power or voltage to keep up the necessary skills.) When I say torque is not important, I mean not as important as some seem to believe. In particular not important enough to require a torque wrench on any connection I make.
In your photo you make the assumption that the initial torque was wrong. I did not do the work. So I will again not comment on the work or the cause of the problem.
While IR testing is better than torque verification, the requirement is torque not performance. I would accept an IR test.
I torque with my battery powered drill with an adjustible clutch. (I use the numbers for repeat settings.) For terminations 30amps and below I know what setting provides a good connection. For teminations 35amps to 200amps I do tests with scrap wire until I am happy with the appearance of the connection. (I check the appearance by disassembling the connection.)
For work over 200amps or 240volts I sub the work out.
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Let me guess and say I'd bet that pic that shows the broken insulation was under torqued not overtorqued. I doubt cold flow had anything to do with it. If you forget to tighten a connection does a torque wrench make any difference??
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Fred,
You just can't use any type of torque wrench to check the torque of an installed electrical connection that directly involves a conductor. Checking the torque on the bolt that holds the lug to the bus or bus bar bolts is ok, but checking the torque on a conductor termination should not be done. The connection relaxs and you will get some additional movement if you use a torque wrench to check it. Once probably won't hurt anything, but some places do this once a year and that will cause problems because the conductor will be damaged.
Don
Don(resqcapt19)
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Don, I understand that. George's original post dealt with an inspector and what I assumed was a new installation inspection. In that situation torque wrenches of the type I use could be used to verify torque values without over-torquing the connection. In my area the equipment isn't energized until the inspection has been conducted and passed. I don't think it is wise to re-torque terminations periodically. Torque to specs upon initial installation and then leave them alone.
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If you are using a battery drill, keep upping the torque until the screw strips on a old sample screw-then set it for 50% of that stripping value. Question: as the battery gets weak, does the torque, say, at level 4.5, change? For large lugs,I use an automotive-type visual torque wrench-I have had problems with the clicking type. Also,I do not see the problem with re-torqueing. 60 inch/pounds is 60 inch/pounds-all day long. I could be proven wrong, but,I think it would take a huge amount of pressure, say, 150% of the torque value, to damage the conductors. Also I thought "cold flow" was the initial electric current when equipment is energized. A connection that is too loose will arc during cold flow, but stop arcing when the wire is heated up. A normal conection will not arc during cold flow. Is that correct?
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George:
NFPA NEC 90-7 says: "It is the intent of this Code that factory installed internal wiring or the construction of equipment need not be inspected at the time of installation of the equipment except to detect alterations or damage, if the equipmkent has been listed by a qualified electrical testing laboratory.
For example Cutler Hammer in the installation instructions state that their connections should be tested for tightness. The reason they give is because in transportation they losten up. They state to test 10% and is they find 1 loose then proceed to test 100%.
I would suggest you advise your contractors to have a torque wrench available for the equipment inspections. What they will neglect the most are bus connections.
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![[Linked Image from sheldonbrown.com]](http://www.sheldonbrown.com/images/tork-calibration.gif)
