277volt and 480volt wiring without a neutral

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mikebourland

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All,

I have a question regarding 3 phase power without the use of a neutral. I received a question asking if it is proper to wire a 480v parking lot light using only 2 hot conductors (=480v single phase?) and a ground. The other hot leg and neutral are going elsewhere in the facility so a neutral is not available.

In general, I am unsure when a neutral is needed and when it is not. I know there are 3 phase wiring systems that do not have a neutral at all. I think they work off the principal that while 1 phase is providing power, another phase is handling the return voltage.
 
mikebourland said:
All,

I have a question regarding 3 phase power without the use of a neutral. I received a question asking if it is proper to wire a 480v parking lot light using only 2 hot conductors (=480v single phase?) and a ground. The other hot leg and neutral are going elsewhere in the facility so a neutral is not available.

In general, I am unsure when a neutral is needed and when it is not. I know there are 3 phase wiring systems that do not have a neutral at all. I think they work off the principal that while 1 phase is providing power, another phase is handling the return voltage.
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480V phase to phase for a light is basically the same as 240V for your water heater.

Technically speaking you don't "need" a neutral ever to make something work and there are some specific rules about how the grounded/neutral conductor is treated, but there's nothing magical about it, it's just another circuit conductor.
 
The difference is, you will need a 2 pole circuit breaker for the 480V feed, vs a 1 pole breaker for a 277V feed. Same number of conductors of course, but you take up more space in your panelboard.
 
LarryFine said:
Welcome, and it's commonly done that way.

The neutral/ground bond must be done.
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Heres the issue. Currently to this outside light, there is a single phase 480 system and a ground wire. Someone ordered a replacement light that operates at 277v. Would it be possible to use 1 leg from the 480 which is 277 and for the return use the ground conductor? Ive always been told that the ground circuit shouldnt be used as a common return, only for safety purposes only. So the question is, can I use 277 leg and a ground to power outside light? Id think no, but would like advice from yous. Thank you.
 
mikebourland said:
...... So the question is, can I use 277 leg and a ground to power outside light? Id think no, but would like advice from yous. Thank you.
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Absolutely no. What you are calling a ground is more properly called an equipment grounding conductor, and as you've been told, it is there for the purpose of clearing a fault only.

You can pull new wire, you may even be able to re purpose one of the existing hot conductors, even better, just get a light that works on the voltage you have already.
 
ggunn said:
Seriously? Using the EGC as a neutral? I didn't think that was ever OK.
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No, I meant it's common to supply a load with two line conductors and no grounded conductor.

Read the OP and the question I was answering; no mention of using the EGC as a circuit conductor.
 
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