210.6(d)

[Mike01]

600 volts between conductors:

circuits exceeding 277 volts, nominal, to ground and not exceeding 600 volts, nominal, between conductors shall be permitted to supply the following.

(1) the auziliary equipment of electric-discharge lamps mounted in permanently installed luminaires where the luminaires are mounted in accordance with one of the following:


(1)(b) not less than a height of 6.7m (22ft) on poles or similar structures.

So does this mean paking lot fixtures mounted under 22' cannot be provided as 480V-1ph fixtures? that makes it tough on projects where the local ordance restricts your height and you have a large site. is this correct??

 

[iwire]

So does this mean parking lot fixtures mounted under 22' cannot be provided as 480V-1ph fixtures?

No, it does not mean that.

480 volt fixtures supplied from a Wye system do not exceed 277 volts to ground.

Now if for some reason you had a corner grounded delta supply you could run into trouble.

 

[coulter]

...480 volt fixtures supplied from a Wye system do not exceed 277 volts to ground. ...

Solidly grounded Y only or does that include impedance grounded as well?

carl

 

[iwire]

Solidly grounded Y only or does that include impedance grounded as well?

carl

You would have to tell me. :-?

I assume the nominal system voltage of an impedance grounded 480 system is still 277 volt?

 

[CAPS]

Single phase (L-N) loads cannot be served from a resistance/impedance grounded system. It is in article 250, but I don't have my codebook handy.

 

[iwire]

I did not know that, thanks.

250.36

 

[coulter]

Single phase (L-N) loads cannot be served from a resistance/impedance grounded system. ...

CAPS -
That's great. And yes most of us knew that. And that has nothing to do with the OP or the following three posts.

Could I respectfully ask you to read the thread before replying and to reply in context?

carl

 

[CAPS]

iwire,
Thank you for your post. I always find your posts insightful and informative.

coulter,
I'm sorry if my post annoyed you. Unfortunately, YOU were the one that inquired about an impedance grounded system. I was only trying to point out that 277v lighting could not be connected to that system. I, like many others, use this forum for self improvement since I don't know everything.
I still hope you have a great day.

 

[coulter]

...I'm sorry if my post annoyed you. Unfortunately, YOU were the one that inquired about an impedance grounded system. ...

Yes I did ask about using single phase 480V for a 480 impedance grounded system. I am still asking. Your post didn't annoy me, it just didn't help.

The question is about 480V single phase not 277V single phase. This comes up every now and then and when it does I think, "Hey, maybe there is someone that knows the answer to this." Alas, they may, but I'll never know, because so far, every one has answered the question with, "No you can't use 277V, 1ph on impedance grounded 480V."

Now, if you have knowledge or insight on using 480V, 1ph circuits, on an impedance grounded system, I'm interested.

Either way, I'll have a great day

carl

 

[LarryFine]

Carl, as Bob suggested, I'd agree that an impedance-grounded Y system is considered to have the same nominal voltage to earth as a solidly-grounded Y system.

The system neutral resistance is bound to be of a lower impedance than the voltmeter you're likely to use to check it, so you'd read the nominal phase-to-ground voltage.