277 volts on one phase

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mbrooke said:
I have, and I apologize if you are being genuine.

However no offense but the questions you ask along with working live get me concerned. This need to be done correctly and no its never ok to work live.
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I am glad that electricians will say that.

Even if I didn't plan on it. Sometimes things that go on at jobs, if I talk about them, I can find out how electricians around the world feel about them.

Like i said, since it happened, little things like wiring a box or light while it is hot at every electrical company I worked for, I didn't expect it to be an issue.
Before I started new construction, I never wired anything hot.

I would hear others say they did, and ask them why. Why not just turn off the breaker.
 
degupita said:
I am glad that electricians will say that.

Even if I didn't plan on it. Sometimes things that go on at jobs, if I talk about them, I can find out how electricians around the world feel about them.

Like i said, since it happened, little things like wiring a box or light while it is hot at every electrical company I worked for, I didn't expect it to be an issue.
Before I started new construction, I never wired anything hot.

I would hear others say they did, and ask them why. Why not just turn off the breaker.
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To please the client. Its an unfortunate fact but not everyone wants a place to go dark or have something off line.
 
jbelectric777 said:
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!
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FWIW, a milliamp is a thousandth of an amp, not a millionth. I am not a doctor, but I don't think a few microamps (millionths of an amp) of shock will stop your heart.
 
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degupita said:
You never had to work a job or contract where you didn't ever work on live circuits?

Because every company I worked for, big or small, I had and the other electricians I worked with did.

It goes like this. If the circuit is hot, and you want to undue the wires. Un-grounded hot phase first. Then grounded neutral.

If you want to connect the wires. Grounded neutral first, then ungrounded hot.
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That all sounds nice, but but if you have not shut off all three circuits sharing the same neutral and break the neutrals, you'll could be in a bad way fast.
Dont learn it the hard way, it might end up being you last lesson learned.
 
Wow! That's all I can say....having been a utility electrician for over 40 years, I've worked lots of 3 phase, 120/208 and 277/480, 480 Delta, etc. But one thing I learned VERY early on is never to take ANY voltage for granted. I've seen co-workers seriously injured on 120 as well as 480. PPE was not a really big deal back in the day, but now that it's the law, it just may save your life. Easy to find excuses for not using it when working hot, but no real good reasons. There are times when hot work is required (testing or troubleshooting are a couple), but if you can, work it dead! Dead means "Identify, Isolate, Test, Ground (if necessary) and Tag". Your attitude scares me because I don't think you have enough respect for what you do...sorry, but that's my opinion.
 
mbrooke said:
11:18 :eek:


https://www.youtube.com/watch?v=mpgAVE4UwFw
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50 microamps directly across the wrong parts of the heart, yes, possible. But unless you open the chest cavity to do that, 50microamps between two points on the skin will not come anywhere near posing a danger to the heart.

So, IMHO a true statement, but misleading in the context of shock exposure while working live.
 
GoldDigger said:
50 microamps directly across the wrong parts of the heart, yes, possible. But unless you open the chest cavity to do that, 50microamps between two points on the skin will not come anywhere near posing a danger to the heart.

So, IMHO a true statement, but misleading in the context of shock exposure while working live.
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I agree it can be misleading, but at 277 volts passing 100ma through two points of the body that could cause 50uA across the heart is a realistic expectation.
 
Electric current is sometimes very favorable to a heart. When a human heart is fibrillating, a strong pulse current of several thousand volts can bring it back to normal beating again. So what causes death by electric current, other than from burns injury, is the damage it does to the nerves controlling respiration and consequently stopping the heart.
 
degupita said:
It is the idea of 277V on one phase.

Can there be 480V on a phase/neutral, or is that phase to phase?
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This is nothing new - you just have not been introduced to it before.


degupita said:
You never had to work a job or contract where you didn't ever work on live circuits?

Because every company I worked for, big or small, I had and the other electricians I worked with did.

It goes like this. If the circuit is hot, and you want to undue the wires. Un-grounded hot phase first. Then grounded neutral.

If you want to connect the wires. Grounded neutral first, then ungrounded hot.
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I don't disagree that this don't happen. But all it takes is one mistake and you have a dead worker. This is followed by OSHA investigations, or at very least the department of labor in the state you are in, most likely heavy fines for worker safety violations - and they will find more then just improper hot work to fine the employer for, then that is followed by wrongful death lawsuits by the family of the deceased. Plus the family of the deceased has a loss that can never be replaced with any amount of money.

Kind of makes careful planning and timely shut downs look pretty inexpensive.
 
Sahib said:
Electric current is sometimes very favorable to a heart. When a human heart is fibrillating, a strong pulse current of several thousand volts can bring it back to normal beating again. So what causes death by electric current, other than from burns injury, is the damage it does to the nerves controlling respiration and consequently stopping the heart.
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True, but a DC pulse is used in medical setting while line current is AC. AC paralyzes muscles and Id imagine its similar for the heart. A DC shock on the other hand is a sharp muscle contraction.
 
your right - a milli-amp is one thousand of 1 amp, my mistake..... GFCI OUTLETS are set to trip at 4-5ma between the ungrounded conductor and any ground. (that's why they are used for replacement of the old 2w outlets where there is no EG) now that said, wouldn't it serve better to PM me instead of that big description of opening a heart and putting 5ua across it? in case you aren't familiar ua is micro amps - so instead next time just say "I think you mean ma (milli) not ua (micro) and yes I do know the difference.
 
I don't profess to be a medical expert, but we as a utility have AED's (Automatic External Defibrillators) on most of our trucks. Reason being that a shock from ANY source can cause the heart to quit beating in a regular pattern. The victim WILL die if CPR or defibrillation doesn't happen within a few minutes. AC or DC...not much difference as far as sending a heart into fibrillation. It all depends on the current AND the individual. According to our safety instructors, it is successful in only a small minority of electrical injuries. No way of knowing which kind of victim you'll be. Worth the risk? Just my opinion, though. If yours is different, I'll quietly explain why you're wrong.:p
 
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kwired said:
This is nothing new - you just have not been introduced to it before.
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I don't mind the comments about electrical safety, like the one below. But as far as how much I know, what experience I have had, what job environment I am working in, and whether or not something is over my head, people do not know what they are talking about.
This isn't really based on the comment here. But if I mention about 277V on one phase, I don't feel a prudent electrician should assume that I don't know what I am doing, don't know how to use a meter, don't know what PPE to use, and various other assumptions. If that is how they handle their electrical jobs, they are making a lot of mistakes.
Ask. Find out.

I like to fully understand electrical subjects, and sometimes I need a tidbit from something that may seem 101 to certain veteran electricians. But this tidbit may help me understand it in a way that may surpass and give a wholistic perspective I didn't have before. This happened at another place where I asked about the grounded neutral in relation to more than one circuit. What I was asking about no one really got. They thought I didn't know about multi-branch circuits, or gave me information on an open neutral, or just didn't know what a neutral was. I wasn't really able to get what I needed there, so I had to look elsewhere. It happened with another subject to, an analog meter I have.
With both I got the wise, all knowing electricians saying, "hey little buddy, you better not mess with that, you don't know what you are doing or what could happen"
I know people cannot tell with unknown posters coming in, but that is where ask, find out comes in. Before you tell them they don't know what they are doing.






I don't disagree that this don't happen. But all it takes is one mistake and you have a dead worker. This is followed by OSHA investigations, or at very least the department of labor in the state you are in, most likely heavy fines for worker safety violations - and they will find more then just improper hot work to fine the employer for, then that is followed by wrongful death lawsuits by the family of the deceased. Plus the family of the deceased has a loss that can never be replaced with any amount of money.

Kind of makes careful planning and timely shut downs look pretty inexpensive.
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Of course.
 
degupita said:
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.

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.
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degupita said:
I don't mind the comments about electrical safety, like the one below. But as far as how much I know, what experience I have had, what job environment I am working in, and whether or not something is over my head, people do not know what they are talking about.
But if I mention about 277V on one phase, I don't feel a prudent electrician should assume that I don't know what I am doing.
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Yes a prudent electrician would assume you don't know what you are doing, when it comes to working with 480-277 V three phase. Your comments suggest that you don't have any experience at all working with this voltage level.

No one said that you are not an experienced electrician. You may be very well qualified in other areas of electrical work. None of us know everything and there are areas of electrical work that we haven't done. I've been at it for over 40 years and there are things that I have no experience with.

I know many people that can drive a car but they are lost when it comes to driving a big truck. That doesn't mean they don't know how to drive but it does mean they are limited as to what they drive.
 
IMO according to your original post you were just wanting to learn more concerning 480/277 volt system and somehow the topic became skewed off to where we are at now. I think your taking some of the comments the wrong way. No one is saying your not a quality electrician, just that at this time it sounds like your not a qualified electrician to be working on any 3 phase system. No one wants to see you get hurt. The best advice I can give you is, when you have time, sit down with qualified person and have them teach you the ends and outs of multiple 3 phase systems and how to properly work with them. It is also the duty of a good foreman or boss to know their employees strengths and weaknesses and not subject them to tasks they are not properly trained.
 
growler said:
Yes a prudent electrician would assume you don't know what you are doing, when it comes to working with 480-277 V three phase. Your comments suggest that you don't have any experience at all working with this voltage level.

No one said that you are not an experienced electrician. You may be very well qualified in other areas of electrical work. None of us know everything and there are areas of electrical work that we haven't done. I've been at it for over 40 years and there are things that I have no experience with.

I know many people that can drive a car but they are lost when it comes to driving a big truck. That doesn't mean they don't know how to drive but it does mean they are limited as to what they drive.
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Some of us dont know even with experience. Put a PLC or motor drive system in front of me and I loose the ability to turn a screw driver:eek: :dunce:
 
meternerd said:
I don't profess to be a medical expert, but we as a utility have AED's (Automatic External Defibrillators) on most of our trucks. Reason being that a shock from ANY source can cause the heart to quit beating in a regular pattern. The victim WILL die if CPR or defibrillation doesn't happen within a few minutes. AC or DC...not much difference as far as sending a heart into fibrillation. It all depends on the current AND the individual. According to our safety instructors, it is successful in only a small minority of electrical injuries. No way of knowing which kind of victim you'll be. Worth the risk? Just my opinion, though. If yours is different, I'll quietly explain why you're wrong.:p
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I would guess the AED is there for more then just "electrical" related accidents. POCO employees though they may work for a private company, still have a public image in most cases. I know if I were in a vehicle accident on a roadway I would want most any of the area POCO technicians to be be one of those that came up on the scene before the arrival of police, ambulance, etc. - they are all well trained in first aid, CPR, etc. and their vehicles are stocked with emergency equipment and they would use it in such an incident. One POCO employee I know well is even a volunteer EMT - which is what all EMT's are in rural areas like where I live.
 
I have been shocked many times, almost every company I have ever worked for we did a lot of things hot,also rode company trucks that the seat belts did not work and on the way back to the shop drinking like a fish,that's just the way it was at those certain shops. I had a job and that's all that matterd at the time,you guys are bashing this young man for asking a simple ? ,regardless the voltage he knew it was hot,and I'm sure he worked on it like it was hot, his EXP might only be in low voltage residential guy, but he has the concept to ask about something he did not fully understand,it's just a lighting fixture he felt comfortable doing it one hot one neutral 277 or 120 disconnect it one way reconnect the reverse way simple.some people on here are acting like his Forman told him to do a line side tape live,it was a lighting fixture,hopefully he does not lose his confidence do to all the negative feed back
 
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