Disconnecting neutrals

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  #1  
Old 09-08-06, 05:28 PM
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Disconnecting neutrals

A co-worker and I have a little dispute i'd like to resolve. He claims that if one were to unhook neutrals off a 120v outlet that downstream outlets need (but leave the hot lead connected), that devices downstream would burn up because of the loss of neutral continuity. I say it doesn't matter, no neutral, no current flow. Any theories?
 
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  #2  
Old 09-08-06, 05:37 PM
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The receps downstream woulod not "burn up" but they would not work...The neutral is the return path for the electric current without the neutral "it ain't gonna work"
 
  #3  
Old 09-08-06, 06:03 PM
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that only makes sence. To put it just simply, its like switching the neutral on a light bulb.
 
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Old 09-08-06, 06:15 PM
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The only time you have a problem is if the circuit is a multi-wire circuit and the neutral is lost. However, this will not cause the receptacle to burn. It may place 240 volts on a device plugged in, and the device may burn, but the receptacle itself won't be bothered.
 
  #5  
Old 09-09-06, 05:44 AM
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Originally Posted by racraft
It may place 240 volts on a device plugged in

could would explain this in a little more detail? This is what we're debating, not necessarily the outlet itself burning up. We're concerned with items (telephone, fax machine, radio, etc)being plugged into other outlets at same the time that I want to change out another hot outlet.
 
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Old 09-09-06, 05:55 AM
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Originally Posted by racraft
The only time you have a problem is if the circuit is a multi-wire circuit and the neutral is lost. However, this will not cause the receptacle to burn. It may place 240 volts on a device plugged in, and the device may burn, but the receptacle itself won't be bothered.
A multi-wire branch circuit neutral will cause this?
I know that it (240 volts or more) will (sometimes) happen if you lose the service neutral into the main panel, but I've never heard of or seen a branch circuit do this.
steve
 
  #7  
Old 09-09-06, 06:20 AM
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Loosing a Neutral on MWBC is more common than loosing one on a service. I could list the horror stories from this.

One of the large govt facilities were I do alot of contract work has made it clear that they will no longer be installed and if we run into one, we are to report it immediately, so they can write a ticket (work order) to pull the extra grounded conductors needed to eliminate the neutral.
 
  #8  
Old 09-09-06, 06:28 AM
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Originally Posted by nova_gh
could would explain this in a little more detail? This is what we're debating, not necessarily the outlet itself burning up. We're concerned with items (telephone, fax machine, radio, etc)being plugged into other outlets at same the time that I want to change out another hot outlet.
With the power off it is not a concern on any type of circuit. You should not be changing receptacles with the power on ever.
 
  #9  
Old 09-09-06, 06:46 AM
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Originally Posted by joed
With the power off it is not a concern on any type of circuit. You should not be changing receptacles with the power on ever.
Yea what joed said, and since your hands will not make and break a connection as fast as a breaker or switch the pulsing on/off of the electrical ciricuit can cause dammage to equiptment.

nova_gh are you an electrician? Is your boss trying to get you into so much of a hurry that you are not taking time to tell the customers to turn off thier stuff off so you can shut the breaker down and work safely? If so, you have a larger problem than the equiptment issue.
 
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Old 09-09-06, 07:08 AM
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Originally Posted by nova_gh
could would explain this in a little more detail? This is what we're debating, not necessarily the outlet itself burning up. We're concerned with items (telephone, fax machine, radio, etc)being plugged into other outlets at same the time that I want to change out another hot outlet.
The danger is you getting electrocuted when you change a receptacle on a "hot" multi-wire circuit, or any "hot" circuit for that matter.
Remember, the neutral returns the un-balanced load on the circuit. If you leave the circuit (breaker) on (2 pole on a multiwire), the black and red will have 120V potential to ground and 240 volts potential between themselves, although only one, the black or the red (and white), will be attached to the (120V) receptacle.
If any of the downstream loads on the circuit are plugged in and turned on (clock, toaster, telephone, light, etc.), the WHITE will also have 120 volts potential to ground. A multi-wire branch circuit uses (2) 120 volt hot legs that are 180 electrical degrees apart (half turn on a generator armature), which means it uses a circuit where each hot conductor has 120 volts potential to ground and 240 volts potential to the other hot conductor. This is how one neutral conductor can be used to supply 2 circuits on a properly wired Multi-wire circuit without the wire being overloaded.
If both of the hot conductors are equally loaded, the neutral will have zero current flowing (although it still has 120 volts potential to ground). If 1 leg has 20 amps flowing and the other has 5 amps flowing the neutral will carry the un-balance between the two which is 15 amps.
The current is continually fluctuating in the neutral conductor and goes up or down depending on which load is turned on at that moment in time.
The hot legs (black or red) of a Multi-wire circuit must be on opposite legs (bus) in the breaker panel. If your hot wires are connected to the same bus, the neutral wire can be overloaded and cause a fire. That's why Multi-wire circuits should have a 2 pole breaker to supply them. A 2 pole (aka 240 Volt) breaker connects to both poles (bus) in the breaker panel, thus it's not possible to connect the "hot" circuit wires to the same pole. Plus it's not possible to turn off just "half" of the circuit.
In my opinion, disconnecting the neutral to change a receptacle will not damage any downstream equipment that is plugged into a (properly wired) multi-wire circuit. There will still be electrical potential on both the hot conductors (the one that travels thru the box that you're working on, and the one connected to the receptacle that you're holding in your hand, and possibly the neutral, but no return path for the current to flow, unless it happens to be you. If that's the case, you're going to get shocked.
TURN THE POWER OFF! when working on anything electrical.
Just my 2 cents .
steve
 
  #11  
Old 09-09-06, 08:11 AM
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An outlet-box for two 120-volt receptacles is feed by a 3-wire Branch-Circuit. The Neutral (White wire) connects to both receptacles. The Black wire connects to the "Left" receptacle and the Red wire connects to the "Right" receptacle.

A load with a resistance of 10 Ohms is pluged into the "L" receptacle, and a load of 60 Ohms is pluged into the "R" receptacle.

If the Neutral is dis-connected, the 10 Ohm load and the 60 Ohm load are in "series" across 220 volts. With a load of 10 Ohms + 60 Ohms = 70 Ohms, the current = 220 volts / 70 Ohms = 3 amps.

The voltage across the 10 Ohm load = 10 X 3 = 30 volts. (approx)

The voltage across the 60 Ohm load = 60 x 3 = 180 volts. (approx )
 
  #12  
Old 09-09-06, 08:22 AM
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Originally Posted by PATTBAA
An outlet-box for two 120-volt receptacles is feed by a 3-wire Branch-Circuit. The Neutral (White wire) connects to both receptacles. The Black wire connects to the "Left" receptacle and the Red wire connects to the "Right" receptacle.

A load with a resistance of 10 Ohms is pluged into the "L" receptacle, and a load of 60 Ohms is pluged into the "R" receptacle.

If the Neutral is dis-connected, the 10 Ohm load and the 60 Ohm load are in "series" across 220 volts. With a load of 10 Ohms + 60 Ohms = 70 Ohms, the current = 220 volts / 70 Ohms = 3 amps.

The voltage across the 10 Ohm load = 10 X 3 = 30 volts. (approx)

The voltage across the 60 Ohm load = 60 x 3 = 180 volts. (approx )
And that is one way to burn stuff up even just changing out a rec. I have had the neutral wire nut just fall off in the box, opening the circuit. So even on a "properly wired MWBC" this can and does happen all the time.

I have also lost equipment that was down line when making and breaking the connections, on a part of the circuit that was past the MWBC split.

I no longer work on live elec circuits at all. But I am not posting BS above. I have learned these things from experience.
 
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Old 09-09-06, 08:41 AM
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Thanks for the information. After seeing the numbers in black and white and sketching out the circuit I now realize how damage can happen with a open neutral on a MWBC. I never install multi-wire branch circuits (never have) although some electricians swear by them. I've never felt "easy" about sharing a neutral between two hots. I guess I had a good reason although I never really thought it through before this.
The thing that always concerned me most was the chance of someone moving a wire (or breaker) in the panel and placing both hot legs of the MWBC on the same (terminal) buss. If this happens the neutral carries all of the un-balanced load of both hot conductors and can overload and cause a fire.
steve
 
  #14  
Old 09-09-06, 08:54 AM
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Another potential problem, though not likley in residential work, but common in commercial/industrial work, with a MWBC is that if plugged in equipment creates harmonic distortion, you can overload the neutral even though the circuit is "balanced".

For example, an office where most of the loads on the circuits involved are computers.
 
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Old 09-09-06, 09:36 AM
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Don't forget the part that if your mistake brakes it... You own it!
Office stuff and home electronics (as you know) add up fast.
Insurance, only sometimes covers you for ignorance.
Then rates go up,cancled etc.
Makes a $200. service call a bit more than you bargain for.
 
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Old 09-09-06, 10:51 AM
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Wow. I go out for the morning, not realizing I opened a can of worms, and everyone else chimes in address the question.

Multi-wire circuits have their place. They are one way to double the power to an outbuilding (shed, garage, etc.) without requiring a sub panel at the outbuilding.

They also work great if you need to run power a distance before it used. It easier to pull 12-3 than two runs of 12-2, although not that much easier.

My preference for a multi-wire circuit is to split the circuit at the destination, and then run two separate circuit where you need them. While this does not eliminate the possibility of 240 volts across a device, it certainly makes it much less of a possibility.
 
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Old 09-09-06, 11:10 AM
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While I do agree with all of the info given above, I will say that multiwire branch circuits are very common in commercial work. In a 3 phase panel, you even get to use 3 hots to a neut. That means it requires 2/3 the copper to run a 3 phase mwbc opposed to individual neutrals.

One reason this is not going to go away anytime soon is the simple fact of economics. It cost 1/3 more to run individual neuts in a 3 phase situation. When you are talking about the possibility of hundreds upon hundreds of circuits in a given building, we start talking about some major bucks.

Additionally, conduit size is increased do to the increased number of wires. Again, more money.

Until money is not a defining factor in electrical work, mwbc will continue to be here.

The one thing we, as electricians, can control is the quality of the installation to minimize situations such as jwhite spoke of with the wire nut situation.
 
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Old 09-09-06, 06:09 PM
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ges, i read all of this post, and i don't know where or why but it seems that things strayed in a different direction. I didn't mention anything about MLBC or 240V circuits or anything that had to do with Ohms. To basically try to reply to some posts, the reason we (yes i am an electrian apprentice) remove outlets hot, is that 90%+ of our work is done hot. We do everything from changing outlets to 4160V over-head line work. 120V on an outlet doesn't really discourage me from doing my job. And yes, we are pushed to move fast.

i don't really think my question got a yes or no, right or wrong answer, but i did get the general idea that its better safe than sorry.
 
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Old 09-09-06, 06:25 PM
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Remove the neutral and NO the receptical will not burn up.
The ground if there is one will carry the inbalance and where not insulated could heat up the combustables and start a fire. Assumeing there is a load on the ckt.

120VAC kill more people each year than any other voltage.
Not recommended to work on anything live.
1460 live? ABSOLUTELY no reason for that.
138 is the largest I work with and we will not do it live.
Racking a breaker ya. But open the gear.. NO WAY.

Good luck and stick with it. It's a great feild, Lots of oppertunity and a future. Just be smart and safe.
There is a lot of money out there but only 1 you.
 
  #20  
Old 09-09-06, 08:25 PM
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Working hot is against the law!

Originally Posted by nova_gh
ges, i read all of this post, and i don't know where or why but it seems that things strayed in a different direction. I didn't mention anything about MLBC or 240V circuits or anything that had to do with Ohms. To basically try to reply to some posts, the reason we (yes i am an electrian apprentice) remove outlets hot, is that 90%+ of our work is done hot. We do everything from changing outlets to 4160V over-head line work. 120V on an outlet doesn't really discourage me from doing my job. And yes, we are pushed to move fast.

i don't really think my question got a yes or no, right or wrong answer, but i did get the general idea that its better safe than sorry.
In most places in the US working hot is against the OSHA or industrial safety laws. There is no good reason to work residential stuff hot.

Getting back to the original question there are a number of electronic devices that will be damaged if they are connected to a circuit with an open neutral. My employer ended up paying for a number of kitchen devices because of an open neutral on a two wire branch circuit. A microwave, coffee pot, and a clock radio were all damaged.
 
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Old 09-09-06, 08:47 PM
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Originally Posted by lectriclee
The ground if there is one will carry the inbalance and where not insulated could heat up the combustables and start a fire. Assumeing there is a load on the ckt.

.
Huh??!! The ground is not involved in the hot circuit unless there is a ground fault.

The answer to th OP's question.

"that devices downstream would burn up because of the loss of neutral continuity"

The answer is a resounding and definate.....................maybe or if you prefer,possibly. Since you did not ask about a MWBC and if you want to limit the question to single circuits, then no, it will not burn anything up.

sthrnamp answered your question in the very first response if you are only concerned with single circuit neuts.

racraft answered your question if you include MWBC in the second response.

The rest was info for an apprentice that apparently needs to learn that working a circuit hot does not make one macho or smart. The only thing it may make one is dead.

BTW, linemen often work their stuff hot (very often.) I would say to the point that they actually work very little not hot. If done with care and knowledge, it can be acceptable. For them, it is a neccessity in many cases. nova_gh sounds like one of the many hurried sparks that make excuses for working it hot until somebody gets hurt. Then everybody gets real safe for awhile. If you have ever seen a foot blown off or hands damaged beyond use, you would probably reconsider the need to work hot circuits.

For a little demo of the power we all deal with visit this website.


http://electricsubstationsafety.com/photo5.html
 
  #22  
Old 09-09-06, 09:20 PM
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I spent 25 years working for a large industrial manufacturer and the electricians NEVER worked on live equipment.

Prior to that I worked for an electric utility. While it is true that much utility work is done live it is ONLY done so when continuity of service must be maintained. Any time it was possible the circuits were not only de-energized but they were also grounded prior to any work being done.

Unless you are a utility lineworker your employer is WAY OUT OF LINE in requiring you to work on energized circuits.
 
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Old 09-09-06, 10:38 PM
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The ground is not involved in the hot circuit unless there is a ground fault.

this is true Nap. Thanks for catching it.
My mind wonderd back to a trouble call for no heat.
Short of it is. I found 8 GFCI brkrs wired backwards,various hot wires burned off, and all grounded screws holding boxes to wire mesh red hot. (Guys were useing saws and such upstairs.)

Chased a few things and found the service neutral was not ever connected. So the ground was carrying the building (unoccupied) could have been catastrophic. connected the neutral, all GFCIs tripped, repaired all and went on my way.

So NOVA disregard that one statement.
 
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Old 09-10-06, 11:26 AM
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thanks guys, I think i got the post back on track and got the responces I was looking for . Nap, I got your point, I should have phrased my last post to the affect that I didn't see an agreement on an answer. Yes, everyone answered my question, but answered it differently. And yes, I should have pointed out that I was working with a two-wire branch circuit.

And, working on 120V circuits hot isn't my cup of tea, nor do I think it makes me cool or "macho". In fact I find it to be a pain in the ass, with constantly worrying about touching the black wire or shorting to ground. But I don't rank it as difficult to do, so if i need to, i'll work it hot and take my time.

I don't make excuses for anything Nap, if something happens, its my own fault, simple as that. Thanks for the personal attacks and judging me without knowing me too.

I like doing linework, i like doing electrical work in general, and thats why I asked the question in the first place to make me a better electrican. And I do realize the work I do is like working with a loaded gun in my hand. I work with a good crew, we all work to watch each other.
 
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Old 09-10-06, 11:47 AM
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"Thanks for the personal attacks and judging me without knowing me too."

You're welcome. I only responded to your posts and the tenor of your posts. You seemed to be making reasons (read: excuses) to work hot circuits.

I only posted what I did because I have seen the things I mentioned as well as many other things even worse.

In support of your admonishment of me, when I was an apprentice, I worked with this j-man that like the saying," you know, we work with silent death every day. You can't see it. You can't hear it. You can't smell it but is capable of killing you in an instant with no warning" The first time or two I marveled at the wisdom offered. After a week or so, I got tired of it and told him to shut up becasue rather than cautioning me, he now is making me nervous. We all need to realize how serious our line of work can be at any time and treat it like it can kill us. We don;t need to be made to fear it though.

Did you look at the movies on the website I posted? They are awe inspiring.

With the following taken from another poster here, I'll end my input on this thread.

BE SMART............BE SAFE !!!!
 
  #26  
Old 09-10-06, 11:53 AM
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Nova, how can you ever say that you "need" to work a 120v electrical circuit live? We all know that it does not make you macho, in fact it makes you a fool.

Trust me, nap knows you, we all know you. You are the guy who gets hurt, goes on Workman's comp etc and makes all of our insurance rates go up, and OSHA write more restrictive rules for doing electrical work.

Your last post is nothing but white wash for the fact that what you are doing is Illegal, Unsafe, and IMHO Stupid.

Your employer is also to blame. He should care less about his bottom line, and more about your safety. In fact he is a fool, as more often that not, it is actually cheaper to turn the power off, and spend less time changing out the device. It is definitely cheaper than having one man killed. This could loose his entire profit for the entire time he has been in business over one law suit.
 
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Old 09-10-06, 12:35 PM
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#Trust me, nap knows you, we all know you. You are the guy who gets hurt#

JW: Small respectfull objection to the comment.
I beleive we all "KNOW" him, Because we all have been there!
It's an exciting feild and we get comfortable.
The more we learn and understand the more comfortable we get! Nothing wrong with that. Just and always remember what we are dealing with!!! No matter what we know, understand or control, It WILL and CAN sneak up and BITE us in the A--.
The ones who have been around all know of someone they REMEMBER fondly.

LIVE and LEARN!!!!!

Nap: thanks for noticing.
 
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Old 09-10-06, 08:33 PM
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There are OLD electricians and the are BOLD electrcians...
there are no OLD BOLD electricians...Age and treachery will beat youth and arrogance everytime...For what its worth...
 
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Old 09-28-06, 09:58 AM
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Holy #@$$#@XXX

Unfortunately, even I have to chime in here.
Requested to do so too!



Member posted a valid question. And worse yet, had to make mention the topic drifted way off course. Let's answer the question and be done with it.

All side issues have some validity, granted. Working on any live electrical circuitry should be left solely to those whom are as highly skilled, experienced, trained as can be or to those whom may be foolish enough to do so.

Our intentions on this site is to prove the information required to do the job. Not to discuss nor debate among ourselves the pros and or cons, methods, procedures, etc, to death.

One mention of a safety concern is also valid to make note of. Ridiculing or making fun of, belittling, etc. need not apply anywhere within forum topics nor on the site anywhere.

Read the rules gents and please adhere to them. Thanks.

Thank you nova_gh for noting in this thread original question was strayed from.

Thanks to hornetd, in #20 post.
Much apprecaited....

Thanks to all whom have contributed to answering the question.
All of you.

Shame on those whom allowed the question to stray so far off topic. Some of us.

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  #30  
Old 09-28-06, 01:21 PM
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Wow - My brothers got all excited about safety !!
That is Fantastic

break the noodle on a 2 wire circuit and you have lost power down stream -the loads have 0 volts 120 or 277 v.

There is no reason at all to work stuff hot -no need to disscuss voltages over 480 v. since the utility lines belong to the power co and have no code to follow and is certainly not DIYS work

We all have to learn our lesson and I will add that I turn off power mostly because a accident
costs money - more than doing it the proper way and 2nd because my Co. forbids it because of reason #1
 
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