Once again, I encountered some clever person who was able to "create" 110 in a 220v system by grounding the neutral screw to the box. While I corrected the situation, I was challenged to show where this dangerous practice was banned. After all, the NEC does allow uninsulated neutrals (grounded conductors). Other than noting that "raceways" contain, rather than act as, conductors, and noting that the code has no ampacity tables for EMT, I am at a loss as to just where this practice is explicitly banned. Considering that I was once fired for objecting to this practice, I sure would like some better references. Any suggestions?
I do not recall seeing such a statement, but neither do I see where explicity permitted.
The only reference I am aware of - of metal raceways being a conductor is for Equipment Grounding Conductors (EGC), 250.118.
Along the above thought; 250.24(A)(5) does not permit the Grounded Conductor to be re-grounded after the Service Disconnecting means, but does have exceptions. I do not think most installations where the raceway would be used as the neutral could be free of being grounded somewhere.
I do not see metal raceways as conductors in Article 310, Conductors for General Wiring.
Re: Using EMT as neutral#85773 08/06/0307:00 AM08/06/0307:00 AM
Explicity banned. I do not recall seeing such a statement, but neither do I see where explicity permitted.
This maybe come a problem in future codes. Starting with the '05 code, the "uses permitted" will be deleted from some code articles. The idea is that if the code does not prohibit the installation, it will be permitted. Don
Re: Using EMT as neutral#85774 08/06/0308:30 AM08/06/0308:30 AM
Funny that this topic surfaced.... Years back, I had a employee who "went on his own".
Got a call from a job he worked on, arcing behind the clothing racks along the wall. Went to the site, saw visable arc tracking on the 1/2" EMT....went to the AC receptacle, opened the 1900 cover. A new cost cutting installation method.... a great discovery.
One (1) #10 THHN, black, on the single receptacle, a 6" piece of white, from the neutral recept terminal, to a ground screw in the box. Gee, 120 volts at the outlet..
Hmm, materials cost saved? maybe $10.00, possible fire damage? priceless.
Now if he only made sure the setscrews were all tight, he might have escaped!
THe "old timers" used to call this practice "gipping the ground" "who needs the white wire", "The BX sheath is good enough for a return path".
Re: Using EMT as neutral#85776 08/06/0304:03 PM08/06/0304:03 PM
Article 200.2: All premises wiring systems, other than ..... shall have a grounded conductor that is identified in accordance with 200.6. 200.6 seems to only list "insulated" conductors. The definition of "conductor, insulated" in article 100 would not include conduit.
I left out a lot of exceptions in 200.2 that I didn't feel like typing.
Re: Using EMT as neutral#85777 08/15/0305:27 PM08/15/0305:27 PM
Where the NEC discusses the marking of the grounded conductor, is the color shall be, where insulated,.... This seems to suggest that the neutral need not be insulated. I agree that I've only seen an un-insulated "neutral" on the POCO side of the service.
How did I "convert" 240 to 120? I was lucky in that the panel was a main panel, so the ground bus also qualified as a neutral bus. All I had to do was identify one of the wires, mark it, and terminate it in the appropriate places. On a follow-up visit, the manager told me that the maintenance guy had tried to get in the apartment to see "what I'd done," but she had refused him. I thanked her, explaining that it had been necessary for me to do work at both the apartment and the panel in order to make the change.
Re: Using EMT as neutral#85778 08/18/0308:50 PM08/18/0308:50 PM