Wire type EGC in the NEC

retirede

Senior Member
Location
Illinois
FWIW, they only time I’ve ever seen expansion joints install on a metallic raceway was when the raceway crossed a corresponding mechanical joint in the building structure.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician


Ok, I understand you want an answer, I think its fair.

I no longer do any service work, however when I did I believe I saw enough drop ceilings and new/existing work to know that a) conduit can become disconnected b) expansion joints are rarely deployed. In the blueprint work that I do now, I can tell you expansion joints are exceptionally rare over all.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
For as much attention to detail that is usually presented here, not just "for arguments sake", it's obvious when somebody is dodging a question. I'm a newbie and an outsider so I tend to just sit back and watch, but this one has me laughing. It's very clear there are many experts here and most stick to the point of this forum, NEC code references. It's the reason I found this forum, and more than any other resource this has helped me understand and digest this technical subject matter. It's also clear when people just want to argue over opinions, I'm getting the sense that some of the experienced members are "over it."

I appreciate all of the technical experience shared here. The occasional entertainment is a bonus. Thanks for sharing!


I'll be honest on where things stand. Long time masters are not overly thrilled with my technical interpretation of NFPA-70, especially when they paint existing installations with a broad brush as possibly having code violations through differences in interpretation of code language, so the reaction for long time trades men is to distance themselves from oppositional debate.

I stand by my assertion that wire type EGCs having grown in popularity is with reason, even if going against wisdom.

My goal is not be be argumentative or to prove others wrong, but rather elucidate my point of view which I am always more than willingly to allow be challenged from a technical perspective.

No hard feelings toward anyone. :)
 

tom baker

First Chief Moderator
Staff member
For as much attention to detail that is usually presented here, not just "for arguments sake", it's obvious when somebody is dodging a question. I'm a newbie and an outsider so I tend to just sit back and watch, but this one has me laughing. It's very clear there are many experts here and most stick to the point of this forum, NEC code references. It's the reason I found this forum, and more than any other resource this has helped me understand and digest this technical subject matter. It's also clear when people just want to argue over opinions, I'm getting the sense that some of the experienced members are "over it."

I appreciate all of the technical experience shared here. The occasional entertainment is a bonus. Thanks for sharing!
Appreciate comments, we may get off track, but it's mostly business here.
 

tom baker

First Chief Moderator
Staff member
Ok, I understand you want an answer, I think its fair.

I no longer do any service work, however when I did I believe I saw enough drop ceilings and new/existing work to know that a) conduit can become disconnected b) expansion joints are rarely deployed. In the blueprint work that I do now, I can tell you expansion joints are exceptionally rare over all.
Then update your occupation...
 

Fred B

Senior Member
Location
Upstate, NY
Occupation
Electrician
Ok, I understand you want an answer, I think its fair.

I no longer do any service work, however when I did I believe I saw enough drop ceilings and new/existing work to know that a) conduit can become disconnected b) expansion joints are rarely deployed. In the blueprint work that I do now, I can tell you expansion joints are exceptionally rare over all.
Not to dismiss your visually seeing EMT conduit being disconnected, I too have seen it but, none have I seen that is explained by thermal expansion. Every case has been the results of either intentional misuse (ei someone suspending unacceptable weight onto box or pipe or an attempt to adjust a different termination resulting in a connection to separate, or improperly using EMT to be the support for a fixture box). Or, failure to provide proper supports or improperly terminated or coupled connections, these situations usually also need the first case to accompany for connections to actually fail and pull apart.
Lastly a failure from improper mechanical execution of work, ei pipe too short for it to reach into connector to be secured, again needing factors other than thermal expansion. Been into service calls or new work addition and have been surprised by a box connection seperate as I am working to change a fixture only to find the set screw fully set but miss the pipe, but even then the pipe never thermally seperated.
As opposed to PVC, have seen lots of failures solely attributable to thermal expansion/contraction breaking the connections of the conduit, even on short peices that emerge from below grade to a fixed box 3 to 6ft above grade. Or bowing of PVC because of thermal expansion on horizontal runs.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have seen a fair amount of EMT that is undone. It seems pretty common to me. I don't know if it is poor workmanship or just the way it is with EMT that get beat up a little. It does not seem to take a whole lot for it to come apart.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
IMO disconnection comes more from other trades working in drop ceilings worsened by screws that were never tightened well. Vs expansion and contraction though a do believe that IMO it can play a role.

Expansion and contraction in my humble view however contributes to rising R over the years, in that the conduit is forced to move in the fitting slightly whereby the original cold weld is broken.

I want to say this: I could be wrong in reality. Reason being I've never actually used a Siemens (conductance) meter or a earth fault loop impedance meter on new and old conduit. I wish I could and compile the results, but as folks know on here testing is not required by the NEC. I do not even own an EFLI meter.
 

Buck Parrish

Senior Member
Location
NC & IN
We use br
IMO disconnection comes more from other trades working in drop ceilings worsened by screws that were never tightened well. Vs expansion and contraction though a do believe that IMO it can play a role.

Expansion and contraction in my humble view however contributes to rising R over the years, in that the conduit is forced to move in the fitting slightly whereby the original cold weld is broken.

I want to say this: I could be wrong in reality. Reason being I've never actually used a Siemens (conductance) meter or a earth fault loop impedance meter on new and old conduit. I wish I could and compile the results, but as folks know on here testing is not required by the NEC. I do not even own an EFLI meter.
We use expansion joints with braded copper clamped tightly from one conduit to the other with the expansion fitting in between. You never loose continuity .
 

jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
I rarely see EMT with compression fittings. I see mostly set screw and sometimes the style that had a dimple that held the fitting to the tubing.
I think compression & set screw are both ok if tightened properly & securely mounted to boxes. Compression are better for blowing air & much better if you have to “cheat” length on a conduit, as in adding to the middle. But the little rings are a pain & I have seen them slip into the pipe. Also awkward to use together with 1 hole straps. Set screw are lower profile.

I have seen just a few old runs with dimpled fittings but never used them. Secure but irreversible. My very first tool list had the crumpet as an item but the boss scratched it off, said they had quit using them. Someone here ousted a pic of a crumpet awhile back.
 

jmellc

Senior Member
Location
Durham, NC
Occupation
Facility Maintenance Tech. Licensed Electrician
I think compression & set screw are both ok if tightened properly & securely mounted to boxes. Compression are better for blowing air & much better if you have to “cheat” length on a conduit, as in adding to the middle. But the little rings are a pain & I have seen them slip into the pipe. Also awkward to use together with 1 hole straps. Set screw are lower profile.

I have seen just a few old runs with dimpled fittings but never used them. Secure but irreversible. My very first tool list had the crumpet as an item but the boss scratched it off, said they had quit using them. Someone here ousted a pic of a crumpet awhile back.
Sorry, crimper, not crumpet. Wish the site allowed editing after the fact.
 
I have seen a fair amount of EMT that is undone. It seems pretty common to me. I don't know if it is poor workmanship or just the way it is with EMT that get beat up a little. It does not seem to take a whole lot for it to come apart.
I'm not saying you are full of it or anything, guess it just depends on what one has come across. But I actually can't remember the last time I saw an EMT coupling pulled apart,. And I tend to work in a lot of old light commercial spaces with lots of EMT, where it just seems like the original install and the future maintenance was more on the hack side. The last few years on and off I've been working in a 1970s office building with lots of EMT very minimally supported on tie wires, don't think I've seen one of those pulled out.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
Licensed Electrician
I've done a ton of service work and remodels on 60s, 70s, and 80s vintage commercial spaces. All emt, all with no green wire in the conduits and nearly all with no problems. Where there is problems with broken fittings and pulled apart pipes there is other signs of neglect or misuse present.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
It was at one of his seminars. I have been to at least 10, so can't pin it down
Ask him you might get an answer.

He may have also been discussing a completely ungrounded system.

Likely not practical for residential systems, when you consider issues such as incidental contact with distribution voltage, static discharge damage to insulation, leakage current, etc.

But if you had an intact ungrounded system, the risk of shock from 120V circuits would certainly go down.

Once you include the invariable leakage current and insulation decay, and the maintenance involved with its associated cost, an ordinary grounded system probably provides better 'practical safeguarding', however ungrounded systems are used in specialized situations such as operating rooms.

Jon
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I'm not saying you are full of it or anything, guess it just depends on what one has come across. But I actually can't remember the last time I saw an EMT coupling pulled apart,. And I tend to work in a lot of old light commercial spaces with lots of EMT, where it just seems like the original install and the future maintenance was more on the hack side. The last few years on and off I've been working in a 1970s office building with lots of EMT very minimally supported on tie wires, don't think I've seen one of those pulled out.


I did a remo years ago on an old office building. Everything was wiring with 1/2" emt and there was not one strap in any of the runs. The conduit would go thru the steel truss and then lay across the ceiling grid then go back up again. For the most part the connectors were still holding the pipe but I wouldn't bet on it being a good ground. A few pipes had pull apart because the installer never tightened the screws.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I'm not saying you are full of it or anything, guess it just depends on what one has come across. But I actually can't remember the last time I saw an EMT coupling pulled apart,. And I tend to work in a lot of old light commercial spaces with lots of EMT, where it just seems like the original install and the future maintenance was more on the hack side. The last few years on and off I've been working in a 1970s office building with lots of EMT very minimally supported on tie wires, don't think I've seen one of those pulled out.
All of my work is industrial. Over the years I've posted several pictures here of EMT that has come apart. Never seen that happen with threaded conduit. I do recall running across some threaded conduit that was broken though. No idea how they managed to break it. Maybe it got whacked by a truck or something.

I don't get overly excited about it though. I can't do anything about it so what would the point be to getting all worked up over it.
 
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