277 lighting

[mefalk55]

Hello Fella's, I hope I can ask this question without to much back-lash. But I have worked for many years as an Industrial Electrician. At this point in my
career I need a heads up on some info. that will help me get by my new employer. And only you people can help me. Cause I don't want to tell my Boss that I have never worked with 277V lighting. I started a new job and this perticular job was started by a guy who has since BAILED on them. Is this 277 Volts 1 hot wire connected to breaker and a neutral? Or 2 hot wires and neatral? I have worked 220v single phase, 480 3 phase, and 208 3 phase but I must admit that 277v is new to me. Please understand I am in my 50's and have not dealt with 277v systems at all. Thanks for any schooling you can give an OLD MAN! Mefalk

 

[480sparky]

277 is one ungrounded (hot) and one grounded (neutral).

 

[electricalperson]

be very careful with 277. its very dangerous. a 277 volt circuit is a hot and a neutral. similar to 120 volt lighting in a house or light commercial building.

 

[augie47]

if you are familiar with 208 3 phase (assuming 208Y/120), you can approach 480/277 the same way.. 480 phase to phase, 277 any phase to grounded.

 

[rx78757@yahoo.com]

277

277

be very careful with 277. its very dangerous. a 277 volt circuit is a hot and a neutral. similar to 120 volt lighting in a house or light commercial building.

I thought 480 you divide by 1.73 will give you 277V. Each phase will feed each row of lighting. 277 is phase to neutral.

 

[mefalk55]

277volts

277volts

ok, THANKS FOR THE HEADS-UP PEOPLE, I understand..... 1 leg hot the other neutral. This link is worth millions.

 

[electricalperson]

I thought 480 you divide by 1.73 will give you 277V. Each phase will feed each row of lighting. 277 is phase to neutral.

thats correct. same thing with 208. 240 single phase divided by 2 is 120 to ground or neutral. reason why i said its similar to 120 is that you use pretty much the same wiring methods when wiring lights

 

[mattsilkwood]

i remember the first time i got hit with 277 OUCH. i was gunshy for about two weeks

 

[LarryFine]

reason why i said its similar to 120 is that you use pretty much the same wiring methods when wiring lights

The main advantage is that you can deliver more than twice the power on the same circuit size.

 

[peter]

And don't forget you have to use the proper colors. For 480/277 they are usually Brown, Orange and Yellow. And the neutral "grounded conductor" should be gray.
One time they pulled a boatload of 1/2" or bigger cables into a 480v panel and the neutral was taped with white. I told them they had to pull it out and replace it with a cable which was properly taped gray.
~Peter

 

[electricalperson]

And don't forget you have to use the proper colors. For 480/277 they are usually Brown, Orange and Yellow. And the neutral "grounded conductor" should be gray.
One time they pulled a boatload of 1/2" or bigger cables into a 480v panel and the neutral was taped with white. I told them they had to pull it out and replace it with a cable which was properly taped gray.
~Peter

was there 120/208 volts in the building?

 

[480sparky]

And don't forget you have to use the proper colors. For 480/277 they are usually Brown, Orange and Yellow. And the neutral "grounded conductor" should be gray.
One time they pulled a boatload of 1/2" or bigger cables into a 480v panel and the neutral was taped with white. I told them they had to pull it out and replace it with a cable which was properly taped gray.
~Peter

This is not an NEC requirement, though.

 

[mattsilkwood]

And don't forget you have to use the proper colors. For 480/277 they are usually Brown, Orange and Yellow. And the neutral "grounded conductor" should be gray.
One time they pulled a boatload of 1/2" or bigger cables into a 480v panel and the neutral was taped with white. I told them they had to pull it out and replace it with a cable which was properly taped gray.
~Peter

the ungrounded conductor can be either white or gray look at 200.6.
and while imo its just makes good sense to use black, red, blue for 120v and brown, orange, yellow for 277 its not in the code.

 

[peter]

Geesh...
I'm just trying to help the guy out and I get this.
It was a gambling casino and there was probably 120/208 present. Most building are like that for some reason?
As for you other two wild cards-- note that I said "usually" and "should" instead of an imperative "must" or "shall". Nevertheless, thanks for your replies.
Incidently, I never found out whether they pulled out the mis-taped piece of cable.
~Peter

 

[iwire]

was there 120/208 volts in the building?

Have you ever worked in a building that had a 480Y/277 service but did not have any 120 volt power? :-?

 

[ashtrak]

Dangerous.............

Dangerous.............

be very careful with 277. its very dangerous. a 277 volt circuit is a hot and a neutral. similar to 120 volt lighting in a house or light commercial building.

Sitting on some duct work in a ceiling (no other way to reach) troubleshooting a couple of lighting contactors many years ago, hot,sweaty, hand slipped off screw driver handle, wow.......................six broken ribs.

 

[metro2387]

Carefull

Carefull

Be very carefull when working this system. If that neutral is shared you can still get bit if you only turn one circuit off. I believe neutral current is sqroot (a^2+b^2+c^2-a*b-a*c-b*c).

 

[jerm]

I never saw any 277 volt lightning.

Someone should fix the title of this forum, something like "Light[n]ing Protection"