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Discussion Starter · #1 ·
I just wanted to throw this out there and see what everybody thinks about this situation. At the facility I work at, everything is fed from six, 1000KVA, 480v secondary transformers, through switchgear, and then routed out to tap boxes located throughout the facility. From the tap boxes it either runs to 200A three phase load centers or down to lighting panels. This is where it gets interesting. There is not a neutral in this facility. All the 277V lighting is utilized by one leg of the 3 phase and the ground. In each ArmourFlex cable coming to the lighting panels there are three sets of bare ground wires that terminate in the lighting panel. I vaugly remember in school something about a "CN" system or something like that, but thats been 30 years ago. Anybody ever see this type of grounding/neutal set-up before.
 

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Never heard of such a thing but would love to see it. All of the lighting is like this. Sounds fishey to me. Like someone wired them intentionally like that not knowing.
 

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Discussion Starter · #3 · (Edited)
Yes, there is approximately 17 lighting panels that feed 470 1000W MH fixtures. All of the ballasts are wired 277V. One leg going to one phase and the other going to ground. It even shows it this way on the prints from back in the 60's. It is labeled on the drawing as a neutral in the tap boxes, but shows it as a ground wire going to ground bus in the load centers and lighting panels. There is a note at the bottom of one load center drawing that says "green wire had been used for neutral but white is preferered. Anybody else have a clue! All the old hands can say is "Thats how we have always done it"
 

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Discussion Starter · #4 ·
From doing a little Google research, I believe what I have is called a TN-C Earthing System. Please let me know what you think.

 
Combined PE and N conductor all the way from source to the device. The neutral conductor is used as a protective conductor.
It is not permitted for conductors of less than 10 or for portable equipment.
PEN conductor must be connected to a number of earth electrodes in the installation since the TN-C system requires an effective equipotential environment within the installation.
Caution: In the TN-C system, the protective conductor function has priority over the neutral function. Thus, a PEN conductor must always be connected to the earthing terminal of a load and a jumper is used to connect this terminal to the neutral terminal.
 

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Christ, I can't think of how that could have ever been legal in the history of the NEC.
 
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