277 volts on one phase

[degupita]

I just have discovered the concept of something more than 120 being on one phase. I have been doing electrical for years, but didn't have any commercial experience until the last 3 years.

At work today at a store.

I was making boxes for the new light fixtures that would replace the previous cans.

I noticed at the junctions they were marked 277V
I said to the foreman that they must be marked wrong. I have worked with 3 phase, but it hadn't really seen certain aspects of it, or realized that they can be on one phase.

He said all the lights were 277V. Which I then realized why my circuit breaker finder didn't work on them, as I suspect it is only rated for 120V

There are so many lights in that store, and it is big, they need 277V fixtures.
He said, wait to you see 480 on one phase.

Tomorrow I think I will use my meter on it, just to see 277V on a hot and neutral.

 

[roger]

Did your foreman tell you that 480/277 is much more apt to kill you or leave you permanatly scarred than 208/120?

Roger

 

[mbrooke]

Just wondering, are you an apprentice?

Electrical systems can be any voltage. Even though 120/208 and 277/480 is a "standard" you have other voltages and systems of grounding as well. In Canada the standard is 347/600Y.

 

[degupita]

Yes, but I already knew that. It is pretty obvious considering how much more or higher current going through, in a situation like that.

I have done wiring hot, but not 3 phase.

And he said he didn't want to risk doing 277V hot with someone helping him.

So we found the proper breakers for those.

 

[degupita]

It is one thing to read about 3 phase 277/480. But I hadn't actually been face to face with an application like that.

It depends on what you consider an apprentice.

I am a master beginner is the best way I can describe it. I have been doing electrical for 15 years.

It is kind of like, the way I act, people would assume I was a virgin. The same with electrical, I will probably be like this the rest of my life, because I never get jaded.

I always want to understand something more thoroughly.

 

[iwire]

Did your foreman tell you that 480/277 is much more apt to kill you or leave you permanatly scarred than 208/120?

I agree, I work on those systems differently.

 

[mbrooke]

Yes, but I already knew that. It is pretty obvious considering how much more or higher current going through, in a situation like that.

Current wouldn't make a difference. The same circuit could be built on 120 volts.

I have done wiring hot, but not 3 phase.

Chances are you have been working with 3 phase all along as most circuits are shared neutral making them 3 phase.

And he said he didn't want to risk doing 277V hot with someone helping him.

So we found the proper breakers for those.

Thats good, never work hot! Ive heard stories of guys getting hit with 277 and then dropping dead days latter. Dont do it!

 

[mbrooke]

Electric shock / working live

Electric shock / working live

This is a good thread on the subject:


http://www.electriciantalk.com/f12/bad-277v-experience-last-week-118033/

 

[degupita]

It is the idea of 277V on one phase.

Can there be 480V on a phase/neutral, or is that phase to phase?

 

[mbrooke]

It is the idea of 277V on one phase.

Can there be 480V on a phase/neutral, or is that phase to phase?

There can be 480 volts phase to a grounded conductor. A corner grounded delta system is one example.

 

[mbrooke]

I agree, I work on those systems differently.

I approach both the same way: lock out and tag out. (Ok Im being a partial hypocrite, I've worked 120 live like its 5 volts DC )

While you are far more likely to dodge injury at 120 volts, under the right conditions 120 can do you in like 277.

 

[jbelectric777]

Be careful

Be careful

What you are messing with is a 277V branch circuit. The voltage to ground is 277 but between them is 480V. Don't be measuring voltages without the proper experience, it only takes a few millionths of just 1 amp to stop your heart and kill you! Heed what the fellas in here are telling you, if you want to learn and be around electrical wiring then take a job as a helper for a licensed electrician. Or join the local union hall for an apprenticeship. I sure hope you stop what your doing now, I still try to learn something new everyday even after 32 years experience, and nobody knows everything, The very first rule of working as a wireman is to "RESPECT" electricity and your violating it.......hmy:

 

[roger]

It is the idea of 277V on one phase.

Can there be 480V on a phase/neutral, or is that phase to phase?

As mbrooke says, both are possible and with that said, it doesn't matter how long you've been doing some level of electrical work, this is well over your head and dangerous

Roger

 

[degupita]

Current wouldn't make a difference. The same circuit could be built on 120 volts.

There wouldn't be more current on dozens of lights on a circuit of 277V, then if it was a 120V circuit?

Chances are you have been working with 3 phase all along as most circuits are shared neutral making them 3 phase.

That I would like to hear about. How multi-wire circuits are considered 3 phase?

Thats good, never work hot! Ive heard stories of guys getting hit with 277 and then dropping dead days latter. Dont do it!

The 3 phase death punch.

 

[roger]

There wouldn't be more current on dozens of lights on a circuit of 277V, then if it was a 120V circuit?

The opposite would be true, the same amount of fixtures would be drawing more current at 120

That I would like to hear about. How multi-wire circuits are considered 3 phase?

You might have been using three phases and a neutral for a MWBC

The 3 phase death punch.

No, it would be single phase.

Roger

 

[mbrooke]

There wouldn't be more current on dozens of lights on a circuit of 277V, then if it was a 120V circuit?

I can have a circuit carrying 16 amps at 120 volts and another at 277. I can have a 15 amp 277 volt circuit and a 30amp 120 volt circuit and the other way around.

Now, if you mean that a light will draw less current for the SAME wattage at 277 then yes each light will pull less current which means more lights on the same circuit.

That I would like to hear about. How multi-wire circuits are considered 3 phase?

Simple: 3 phases are sharing one neutral. You have 480 between each phase.

The 3 phase death punch.

:lol: Single phase or 3 phase both can a death punch.

 

[degupita]

What you are messing with is a 277V branch circuit. The voltage to ground is 277 but between them is 480V. Don't be measuring voltages without the proper experience, it only takes a few millionths of just 1 amp to stop your heart and kill you! Heed what the fellas in here are telling you, if you want to learn and be around electrical wiring then take a job as a helper for a licensed electrician. Or join the local union hall for an apprenticeship. I sure hope you stop what your doing now, I still try to learn something new everyday even after 32 years experience, and nobody knows everything, The very first rule of working as a wireman is to "RESPECT" electricity and your violating it.......hmy:

I suspect you guys are misunderstanding me.

I am working for a licensed electrical company. I have been working for licensed electrical companies for the last 3 years.

This is a job that the electrical company got.
I didn't put out an ad in craigslist to do some store myself.
Or doing this at some local store for fun.

Take it easy.

I am trying to understand some of the concepts of 277/480 3 phase.

I am also attending the four year course at IEC.

And yes, I know how to use a meter, and if I have the chance to use it, I will do it right there with the electrical foreman.
He can catch my body when I get blown off the ladder.

 

[roger]

And yes, I know how to use a meter, and if I have the chance to use it, I will do it right there with the electrical foreman.
He can catch my body when I get blown off the ladder.

Ok, tell us what PPE your company and foreman would tell you to use before you open a 480Y/277 panelboard and use your meters.

Roger

 

[degupita]

I prefer to have the circuit shutdown and lock/tagged if applicable.

In the store I am working now, the area is sealed off by plastic, it is a construction zone.

Therefore there is no reason we cannot at least shut off a breaker.

Some of the jobs the companies I was with got, were buildings where it would cause problems for a lot of people if you shutdown any circuits. Like city and state buildings. Or construction zones where multiple trades need electrical on the same circuit you are working on.

I have got zapped a few times, screws with your nerves. And the licensed electricians I worked with did also.

It is hard when you are near the top of a ladder, trying to reach up through the ceiling tile metal frame to wire a junction box hot. In a building where people can't have their computers shut off.
Metal tile frame.:huh:

 

[degupita]

Ok, tell us what PPE your company and foreman would tell you to use before you open a 480Y/277 panelboard and use your meters.

Roger

:happysad:

We are not going to be opening the panel-board.

Is that what you thought?

There is no reason to for this job.

What I carry for PPE, regardless of what the companies and foreman say. Is electrical hazard rated gloves. Electrical hazard rated work boots from redwing.
Safety glasses. Long sleeve shirts and pants. A meter that is rated for at-least 750V AC 1000V DC, which I have.

I have the gloves for when it is appropriate to use them, and have even offered them to a licensed electrician that had to hook up a service drop hot.

I don't like my nerves getting shot, let alone my eyeballs boiling.