E.M.T. good for ground

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mdshunk

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jerm said:
what "law" would welding emt break?! some sort of welding statue I don't know about I guess.
Check out 300.18(B)

Every now and again you'll see RMC tacked onto strut and angle iron, which is also a violation.
 

nakulak

Senior Member
most of the chapter 3 methods for conduit say that the installation has to use listed connectors, fittings, etc. welding is not listed as an approved method for connecting the emt (358.6?) That's not to say, however, that it is not a suitable method (90.4) for which you might recieve special permission or be allowed to install under an engineer's supervision ? (just a thought, don't know why anyone would see the need though)
 
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captaincrab55

Senior Member
Location
Maryland
mdshunk said:
Check out 300.18(B)

Every now and again you'll see RMC tacked onto strut and angle iron, which is also a violation.
I had a job 2 years ago where all couplings and entrance points of RMC were welded up to the RF filter... Engineered Drawings....
 

mdshunk

Senior Member
Location
Right here.
captaincrab55 said:
I had a job 2 years ago where all couplings and entrance points of RMC were welded up to the RF filter... Engineered Drawings....
Maybe that was special raceway? Never heard of such, but the code section does leave a little wiggle room for raceway designed to be used this way. I can see how a weld on each fitting for unshielded conductors operating in the RF range would be of some benefit.
 

captaincrab55

Senior Member
Location
Maryland
mdshunk said:
Maybe that was special raceway? Never heard of such, but the code section does leave a little wiggle room for raceway designed to be used this way. I can see how a weld on each fitting for unshielded conductors operating in the RF range would be of some benefit.
It was just regular stock RMC...
 

mistermudd

Senior Member
Location
Washington State
I love it when I am on a old roof & all those old EMT compression fittings have fell apart. Gives me a warm, fuzzy feeling just thinking about all the possible energized metal parts and you know the breakers won't trip because there is no low resistance path back to ground.
 

jerm

Senior Member
Location
Tulsa, Ok
mdshunk said:
Check out 300.18(B)

That only applies if the emt is used for electrical. Welding emt, in itself, is not against any law.

I know, I know, it's an NEC forum, but I wasn't implying welding emt for electrical reasons.
 

captaincrab55

Senior Member
Location
Maryland
pbeasley said:
Isn't stock RMC galvanized? If so, OSHA might have something to say about welding it...
It was galvanized... I don't think OSHA was allowed on that project... BTW, Never did see, meet or talk to the AHJ.....
 

ryan_618

Senior Member
One of the things that often does not get brought up in this discussion is the failure of a raceway that DOES include an EGC. For example, if we pull an EGC in the raceway, and the pipe comes apart, that piece of pipe will remain energized if there is a fault at that location. The simple fact that an EGC is installed does not mean loose fittings aren't an issue.
 

ryan_618

Senior Member
Sure. If you have a conduit system that comes apart, and there is a fault to that isolated raceway, it will never trip, because there is no fault current path back to the source. It would be like taking a stick of pipe that is laying on the ground and touching an energized wire to it.

Example: If you are in an attic that is piped with EMT, and grabbed a piece of pipe that had a bad fitting. If the conduit came apart, it is very likely that it would cut into one of the phase conductors. If that happened, the pipe would be energized, and so would you...the EGC in the conduit would make no difference.
 
ryan_618 said:
Sure. If you have a conduit system that comes apart, and there is a fault to that isolated raceway, it will never trip, because there is no fault current path back to the source. It would be like taking a stick of pipe that is laying on the ground and touching an energized wire to it.

Example: If you are in an attic that is piped with EMT, and grabbed a piece of pipe that had a bad fitting. If the conduit came apart, it is very likely that it would cut into one of the phase conductors. If that happened, the pipe would be energized, and so would you...the EGC in the conduit would make no difference.

View attachment 1209

Is that why we use these? Unless I'm missing something, you would need 2 failures for this scenario to come true.
 

crossman

Senior Member
Location
Southeast Texas
ryan_618 said:
Sure. If you have a conduit system that comes apart, and there is a fault to that isolated raceway, it will never trip, because there is no fault current path back to the source. It would be like taking a stick of pipe that is laying on the ground and touching an energized wire to it.

Okay, thanks for that explanation. I am going to agree with pbeasely. If it was a complete conduit system from panel to load, it would take 2 failures to isolate a piece of conduit like this.
 

Energize

Senior Member
Location
Milky Way Galaxy
OK, the EGC is called out as a # 6 stranded on the approved plans. Boss said forget it, just run the EMT to the six panels in question. Inspector failed the inspection because plans specifically called out the size and type of EGC to be used. Boss started spitting bricks, questioning the inspector's ancestory and lack of "common sense". Inspector smiles, says when you get it corrected, call it back in.

After boss's blood pressure returns to above normal (usual for him), I suggest we contact the engineer and have him write a letter stating it is OK to use the EMT as the EGC. Boss says get back to work, so I return to my duties, wondering why I ever chose this line of work......

Edit: spelling
 

crossman

Senior Member
Location
Southeast Texas
Pierre C Belarge said:
Not necessarily, the break in the conduit could be before the first box.

I guess it depends. I can see what you are saying. I am assuming that the EGC in the conduit was bonded to the last j-box at the outlet, and that the conduit was bonded to the panel. In this scenario, it would require two breaks in the conduit/box system to isolate a piece of pipe.

Am I missing something obvious?
 
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