# Neutrals



## FrunkSlammer (Aug 31, 2013)

Not sure your skill or knowledge level, but here's me making stuff up on the fly...

3phase wye systems use a neutral.. the 3 hots make up a full rotation of a generator at the power plant. 1 hot will make up 1/3rd of that rotation. 

If you use all 3 hots and they are drawing equal current, then no current will flow on the neutral, which carries the unbalance. If you use 1 hot, then the neutral will carry the full amount of the hot. 

A neutral could be undersized if you knew the hots would always be balanced, or the load would be broken. Modern problems in neutrals is harmonics.. digital equipment switching on and off quickly causes undersized neutrals to overheat and burn up. In these cases, the neutrals should actually be OVERsized to compensate. There's also the problem of opening a neutral on equipment.. some equipment won't care or notice, and other equipment will fry on the spot. Never open live neutrals intentionally on any system, EVVVVAAARRRR!!!

Good start? What's your training level?


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## zen (Jun 15, 2009)

I started doing electrical work in 98 got a residential wiremans lisc in 2001. Then in 2005 tdlr or somebody grandfathered j cards I didnt think it was right so I passed on it. Then all the sudden im no longer getting good money or good jobs 2008 to the class for j test after the class I was told 2008 was only good for 1 more month. I didnt take the test. Stayed in resi till it bottomed out . Came to commercial. For 2.5 years and am learning its a whole new electrical world. Most of what I know comes from doing it. No schooling. Thanks that reply really helps

learning to learn


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## zen (Jun 15, 2009)

So 2 a phases on 1 neutral will double the load on the neutral and lighting circuit s with off abd on will be problems as well

learning to learn


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## Bad Electrician (May 20, 2014)

zen said:


> So 2 a phases on 1 neutral will double the load on the neutral and lighting circuit s with off abd on will be problems as well
> 
> learning to learn


No look at the math and calculate for "0" amps on any one phase.

In the statement below (v) should have been the square root symbol

_*I HOPE THE MATH IS CORRECT*_

If you have 
A=0, B=9, C=9 N will equal 9
A=4, B=9, C=9 N will equal 5
A=8, B=9, C=9 N will equal 1
A=100, B=100, C=100 N will equal 0
A=80, B=75, C=100 N will equal 22.9 or 23, no one will argue a 1/10 of an amp. I HOPE?


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## Bad Electrician (May 20, 2014)

*There are several definitions in the IEEE dictionary of standard terms, 7th edition from 2000*
*Neutral (1)(rotating machinery)*
*Neutral-direct current telegraph system (single-current system) ( Single Morse system)*
*Neutral Ground (power and distribution transformers)*
*Neutral grounding capacitor (electric power)*
*Neutral Ground device (electric power)*
*Neutral Grounding Impedor (electric power)*
*Neutral Grounding Reactor *
*Neutral Grounding Resistor (electric power)*
*Neutral Grounding Wave Trap*

*AND*

*Neutral Conductor – *(circuit consisting of *3* or more conductors) The conductor that is intended to be so energized that, in normal steady state, the voltages from every other conductor to the neutral conductor, at the terminals of entry of the circuit, into a delimited region, are definitely related and usually of equal amplitude. _Note: _If the circuit is an alternating-current circuit, it is intended that the voltages have the same period and the phase difference between any two successive voltages, from each of the other conductors to the neutral conductor, selected in a prescribed order, have a predetermined value usually equal to 2πradians divided by the number of phase conductors m. _See also_: network analysis; center of distribution


Hardly going to resolve any discussion or questions EXCEPT


> (circuit consisting of *3* or more conductors)


 That rules out the often questioned single phase 2-wire 120 VAC transformer With a grounded X1 or X2. 

Though I still think in a 2-wire circuit the neutral carries the unbalance of the load. 
L1=9 amps, N=9 Amps.


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## chicken steve (Mar 22, 2011)

Should we go down vector avenue?

~CS~


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## FrunkSlammer (Aug 31, 2013)

Best to find out his knowledge level first to determine how complicated to answer this question. I'm suspecting the OP isn't really familiar with or understanding of the 3phase concept.. that alone makes neutral calculations difficult or impossible to understand.

We might want to start with single phase 120V and split single phase 120/240V.


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## zen (Jun 15, 2009)

Lol. I appreciate everything said and for sure I will value this post until the day I understand all of it. Then I will pass it on. I have only had 2.5 years with 3 phase so im learning. I have been in some places where theres no way who ever half a** worked on it new it was right. Ie 1 a phase in one panel and a b phase in another panel sharing a neutral and no c phase present at all. Seems like all wrong

learning to learn


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## mollydog (Jan 9, 2009)

A very good practice is the grounded conductor pulled and identified with each branch circuit. I know by theory its all good, What I am thinking about is the next pair of hands in that distribution panel that doesn't have your knowledge of balancing shared neutrals aka grounded conductors. We all know the Grounded conductor only carries the difference between phases, balanced as best you can if you must do it at times and an extra step would be to mark /identify that MDP that you have shared neutrals balanced the right way. Also leave your card in the door of the MDP so they call you if there's a problem, it's not code yet but will be, and the correct term is "multi-wire branch circuits" How many times a handy guy gets involved ticks me off so protect yourself.


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## Awg-Dawg (Jan 23, 2007)

mollydog said:


> Also leave your card in the door of the MDP so they call you if there's a problem, it's not code yet but will be,


 What will be code?


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## mollydog (Jan 9, 2009)

*More identification procedures/ Accidents*

:thumbsup:Theres been many, from what I understand, a lot of authors writing in to all code making panels wanting more identification in many areas of the NEC. I didn't write in but think its a good idea, One major change is going to be "multi-wires" and ship to shore power as well as swimming pools. I had an article from Mike H website sent for my opinion about ship to shore installations and I have a lot to say about those areas as well as pools. ie any human submergible construction public and private. The article was a new investigation into why there are so many deaths and accidents to swimmers in the country. My T.O was check/test GFI as manufacturers include in every GFCI box. The other area was inspection of bonding and the GFCI trip/test every season or so many times per year in areas of the country with in use pools and swimming areas year round. I don't know how they plan to do it, I hope contractors to verify in writing all was checked and found safe for introduction of current, but that's not my decision. It's just coming but I don't know when. Also, there are a lot of lobbyists for and against changes as you and I both know. My info came from a good friend involved in the CM panels and stakeholders. It may come to pass, it may not, I don't know but one change coming that I know will be out is UCC section allowing replacement of devices less than 30 amps and a few more conditions that they are adding replacement ground fault devices protecting pool apparatus are not going to be allowed, a permit will be required as well as an inspector or AHJ to physically go to the location and test the GF device in 2 ways, one push the test button and second create an actual fault to assure the device detects it and opens within 4ma. Now don't create a scare or anything, these are items that may or may not come to pass, you know how these things go, but the one thing for sure with changes coming is persons submerged and near AC systems. Take care - Jim


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## zen (Jun 15, 2009)

Any work we and I do on a branch circuit or multiwire branch circuit, I pull a neutral with numbers at every splice point to identify what ungrounded circuit it goes with

learning to learn


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## wcord (Jan 23, 2011)

chicken steve said:


> Should we go down vector avenue?
> 
> ~CS~


Vectors was the absolute worst in school Hated the subject
But it is the proper way to determine the unbalanced load

Here is some heavy reading on using vectors
http://ecmweb.com/content/basics-vector-analysis-part-3

Understanding vectors helped when figuring the perfect spot for the deadman anchor on high tensile fencing ( never used vectors in the filed for electrical :laughing


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## mollydog (Jan 9, 2009)

that's the goodboy way buddy


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## Bad Electrician (May 20, 2014)

mollydog said:


> A very good practice is the grounded conductor pulled and identified with each branch circuit. I know by theory its all good, What I am thinking about is the next pair of hands in that distribution panel that doesn't have your knowledge of balancing shared neutrals aka grounded conductors. We all know the Grounded conductor only carries the difference between phases, balanced as best you can if you must do it at times and an extra step would be to mark /identify that MDP that you have shared neutrals balanced the right way. Also leave your card in the door of the MDP so they call you if there's a problem, it's not code yet but will be, and the correct term is "multi-wire branch circuits" How many times a handy guy gets involved ticks me off so protect yourself.


I agree and think all feeders should be 3 ungrounded conductors with 3 grounded conductors. Because the level of stupidity has reached the point were it seems there are many idiots working in the trade. Lets write the code for any stupid fool that can afford a pair of Kleins.

Lets dumb it down some more


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## Bad Electrician (May 20, 2014)

FrunkSlammer said:


> Best to find out his knowledge level first to determine how complicated to answer this question. I'm suspecting the OP isn't really familiar with or understanding of the 3phase concept.. that alone makes neutral calculations difficult or impossible to understand.
> 
> We might want to start with single phase 120V and split single phase 120/240V.



With the access to the internet and what seems some drive on this posters part he should be able to digest the information given and if nothing else it should motivate his brain matter to delve deeper.


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## ablyss (Feb 8, 2014)

zen said:


> Its common to see 3 hots per one neutral. It was explained to me this works because the ohases arent sharing the neutral at the same time. When we use 2 of the same phases they share it at the same time which is how they burn up. If anyone has time . Any good info on when its ok to share neutrals. Situations where it causes problems and trouble shooting tips to see its been done. Thanks
> 
> learning to learn


Sounds to me like your describing a 208/120Y 3 phase supply, and trying to compare it to a single phase 240/120 Volt supply, and how if any the neutral will handle the loads differently between single phase and a 3 phase.

Quick answer: The neutral in a wye system has another phase to balance, that's all. In a single phase 240/120 system the neutral is balancing the split of the single phase. Technically it's one phase with a center tap, not 2 phases but the neutral treats it as two phases. Confusing right? 

In practice the electrician should balance the loads by placing the breakers so the total combined loads of all the circuits are distributed evenly as possible. This is just good practice, even though the neutral will always be carrying some imbalanced loads.


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## RIVETER (Sep 26, 2009)

zen said:


> Its common to see 3 hots per one neutral. It was explained to me this works because the ohases arent sharing the neutral at the same time. When we use 2 of the same phases they share it at the same time which is how they burn up. If anyone has time . Any good info on when its ok to share neutrals. Situations where it causes problems and trouble shooting tips to see its been done. Thanks
> 
> learning to learn


A better way to explain it is that in a three phase operation even if you are drawing current on all three phases the current will not meet the peak(of each phase) at the same time. Therefore, a properly sized neutral will handle it.


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## mollydog (Jan 9, 2009)

and don't forget if your doing it to use double and/or triple pole breakers and/or approved and listed handle ties as well as down the line the grounded conductor (N) MUST with no exception be pigtailed/hardwired non dependent on the yoke of the device. That's because sharing that (N) you have 2-3 circuits on but still load/current through the other 1 or 2 so an electrician breaking that (N) can get a bad shock, not just the resistance of his/her body, but their body resistance plus any load/s down the line. So in a simple laymens term - Pigtail all neutrals with a wirenut and use 2 and 3 pole breakers on those circuits if you do it. Other than that, use onion and garlic on shrimp overnight as a good marinade.:laughing:


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## zen (Jun 15, 2009)

300 12 is stating this and multiwire would be a, b and c phase sharing a neutral (grounded conductor) . 

learning to learn


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## FrunkSlammer (Aug 31, 2013)

Bad Electrician said:


> With the access to the internet and what seems some drive on this posters part he should be able to digest the information given and if nothing else it should motivate his brain matter to delve deeper.


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## zen (Jun 15, 2009)

For what its worth. No I did not go to any school to be taught . The bottom line is I jacked around to long and other than on here the net and a code book. Thats all I got. Im a good employee never fryed ANYTHING ever. Never blasted any by being stupid or done anything that my boss or any customer have called to say wtf did he do. I dont do anything I dont know how to do. Being older than my supervisors means I may not get any real knowledge. So I learn where I can when I can. Thanks for any help I get.

learning to learn


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## mollydog (Jan 9, 2009)

*This may help*

Your a good tradesman, no worries. I drew this for ya. I hope I can post it and u can read it.


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## chicken steve (Mar 22, 2011)

wcord said:


> Vectors was the absolute worst in school Hated the subject
> But it is the proper way to determine the unbalanced load
> 
> Here is some heavy reading on using vectors
> ...




Agreed we all struggled with vector math in our apprenticeships Wcord

And while i'm no vector wiz, i think it important to maintain the concept , or at least have it in one's head that AC is made & functions in a circle

~CS~
ps~good article!


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## Bad Electrician (May 20, 2014)

FrunkSlammer said:


> WUT


 That the OP has drive and wants to learn, the information posted is not going to damage his mind.

Clear enough for you?


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## FrunkSlammer (Aug 31, 2013)

Bad Electrician said:


> That the OP has drive and wants to learn, the information posted is not going to damage his mind.
> 
> Clear enough for you?


Yeah but if he's far from grasping any 3phase concept, the words and explanations will be over his head. That's why apprentice training schools take so long and work their way up to the complexities of 3 phase. Could be dangerous if he's working around these systems and doesn't understand us either because we didn't explain it properly or he's not even ready to understand it. 

Everything's gotta be an argument around here. :laughing:


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## mollydog (Jan 9, 2009)

For all intended purposes you really dont need all this. Leave it to the Poco. Sure it's good to know but not really needed, all we need is to know is multi pole breakers and (N) pigtailed on the matter as well as balancing branch circuits. Keep it simple and take it from the drop attachment down, thats your baby. Good time to close this thread maybe?


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## Bad Electrician (May 20, 2014)

mollydog said:


> For all intended purposes you really dont need all this. Leave it to the Poco. Sure it's good to know but not really needed, all we need is to know is multi pole breakers and (N) pigtailed on the matter as well as balancing branch circuits. Keep it simple and take it from the drop attachment down, thats your baby. Good time to close this thread maybe?


You are welcome have as little knowledge about MY profession as you wish. Myself I have spent 44 years educating my self and make a living off EC's that keep it simple.:thumbsup:

The electrician came here asking a question and I will answer as I please in depth when I can and correct. I generally do not answer questions I am not 100% sure of the answer. Lastly the typical utility employee could not tell squat about a neutral conductor.


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## ponyboy (Nov 18, 2012)

Bad Electrician said:


> You are welcome have as little knowledge about MY profession as you wish. Myself I have spent 44 years educating my self and make a living off EC's that keep it simple.:thumbsup: The electrician came here asking a question and I will answer as I please in depth when I can and correct. I generally do not answer questions I am not 100% sure of the answer. Lastly the typical utility employee could not tell squat about a neutral conductor.


Atta boy bj


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## mollydog (Jan 9, 2009)

You missed my point.

He just finished saying he was not schooled as of yet formally. He is learning as he goes and most likely all of the theory is going to confuse him when he does have formal education. I take it personal because I worked for a know it all that didn't know anything and when I was a rookie had to re-learn the correct way. Say and do what you want, the topic is going off topic is all and they are going to shut it down soon. As far as your comment on lineman, my comment was for poco engineers not lineman. Try not to be taking things so personal, wasn't meant that way, now theres friction for no reason.


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## zen (Jun 15, 2009)

Ill take the blame for this friction. I do understand that any a question is asked that is well beyond a persons understanding its gonna become a arguement. Ill never be formally trained to do anything at 42 yrs of age. Ill be lucky if I can keep learning enough to be replaced. Those with formal training are fortunate yet usually view my kund as bottom feeders. Those who struggled early on and know where im at offer all the input they can and so its about who really deserves the info . Whatever. Thanks to those who try to help and I understand why others dont think its right. To each their own. Ill find the way ....close this . Ill read and not write

learning to learn


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## Bad Electrician (May 20, 2014)

mollydog said:


> You missed my point.
> 
> He just finished saying he was not schooled as of yet formally. He is learning as he goes and most likely all of the theory is going to confuse him when he does have formal education. I take it personal because I worked for a know it all that didn't know anything and when I was a rookie had to re-learn the correct way. Say and do what you want, the topic is going off topic is all and they are going to shut it down soon. As far as your comment on lineman, my comment was for poco engineers not lineman. Try not to be taking things so personal, wasn't meant that way, now theres friction for no reason.


I had no formal apprenticeship, I read and tried to figure this stuff out, I did take code classes that I paid for and later when I had my own business I attended some seminars and classes. Not taking it personnel but you are asking me to restrict my post because you fear someone you do not know may not grasp the concept. And that just does not compute with me.

I start teaching our apprentices right from the get go, if they ride with me or I am on the job I make sure they are learning more than just installing. 

I do not think I am a know it all but before I give any information to an apprentice, an electrician or customers I make sure I am correct. As much as I like to talk, I try to verify what I discuss regarding our trade 

I worked for electricians when I was starting out that, when asked a question they'd tell me I was to stupid to understand, maybe I was, but give me the information and let me decide if I can decipher it.

I just find it strange that on a site where we are sharing information about our profession, where the subject is something some find confusing, that you would want to limit the information presented and have the post shut down.


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## mollydog (Jan 9, 2009)

I was 15 when I started and climbed the ladder to chief sub code official (electrical) along with plans examiner and my master electricians in both PA and NJ with no formal education and with quitting school in 8th grade taught myself everything while raising a baby @ 17, so I aint no silver spoon case here either jb but darn proud where I came from and what I accomplished! and zen your 42, Im 47 and you can learn anything you want and you don't need school. You can ask me anything, anytime. Im already retired and only want a few hrs a week, Im here to help, not get brow bashed.


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## mollydog (Jan 9, 2009)

*Here Zen, I can send from here.*

When I get better with the sites controls, I'll do this private if ya want. But I have software to show ya and explain just about anything. I hope this helps bud. MS for Zen.png


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## mollydog (Jan 9, 2009)

And yes it's Veppa but it's EKTS version 1.0.3.0 2005 Electrika something. I thing the guy is a Russian Engineer. Have fun !


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## zen (Jun 15, 2009)

Doesnt download to my phone. Probably could on our tablet but my 9 yr old took it hostage and its barely alive.lol. the digram helped me see it better as it would be .we wired a car wash . I worked on the electrical wiring of everything except the relay panel and wbc. I helped pull the wire. Man it was overwhelming how many we pulled to control everything.

learning to learn


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## micromind (Aug 11, 2007)

I've never been an apprentice; just about everything I know about electrical I've learned by reading, asking questions or applying my ideas to the real world. 

You can go absolutely nuts trying to figure out all the idiotic theory about neutral current and it'll do very little for you in the field. 

Here's the actual reality......

In a single phase system, when two hots on opposite phases share a neutral, the current in the neutral will be the difference of the currents in the phase conductors. It will never be higher than either phase conductor.

In a wye connected 3Ø system, the neutral current with one phase conductor will be the same as the hot. 

The neutral current with two opposite phase conductors will be roughly the same as the highest hot. If harmonics are involved, it can be higher, but in real life this is a non-issue.

The neutral current with all 3 phases involved will be less than the highest hot. Harmonics can make it higher, but again, in real life it's not an issue.

You can calculate 3Ø neutral current all day long and still never get the exact value, there are simply too many variables. 

In any system, if two or more hots of the same phase share a neutral, the current will be the sum of the hots. This can be a serious problem.


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## Big John (May 23, 2010)

"Neutral" like "Ground" is a deceiving term. 

Current flows when a potential difference exists. Potential difference exists based on the impedance of the load. There is nothing extraordinary about a "neutral" that gives it special properties. At best it's simply a conductor that has no current flowing on it because no potential difference exists when measured to it, at worst it's just a common phase conductor.

Depending on how imbalanced a load is, and if the neutral point is grounded, you can absolutely have significant voltage measured at a neutral point. The fact that it's called "neutral" doesn't mean it is.


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## zen (Jun 15, 2009)

This is making sense. From the begening I made it a habit to not share neutrals. If it had to be done I would use a 2 pole breaker.resi. Now in commercial I often fin when tracing circuits ill find panel LA 1 CKT 1 and say ckt 9 sharing a neutral. In theory I guess its ok for the phases involved.A and B but not good because of the single pole breakers. How do I efficiently go into these types of remodels and determine if the integrity of the system is sound without spending the next year looking at all the work done to it. With no loads its hard to amp check the neutral. Should in the cases use maybe a corded dril or 2 or 3 . Depending on phases shared to check the neutral load.

learning to learn


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## zen (Jun 15, 2009)

1st. 300.14 b. Would be my previous reference. Now to answer my own question. I guess if I open each panel and count hots vs neutrals that would be a start. Then try to determine how many neutrals vs hots are in each pipe leaving the panel. Would the next thing to do be , find where the circuits go and put a tone at the outlet and see if it tones to the same neutral as any of the other circuits

learning to learn


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## Bad Electrician (May 20, 2014)

Zen

Take a multi-wire branch circuit, measure the current on the neutral, then measure the current on all 3 conductors, they current should be the same. Then on all 3 conductors and the neutral simultaneously.

If you have a large clamp on or a small feeder you could do this on the feeder.


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## Year_Zero (Nov 3, 2013)

Bad Electrician said:


> I agree and think all feeders should be 3 ungrounded conductors with 3 grounded conductors. Because the level of stupidity has reached the point were it seems there are many idiots working in the trade. Lets write the code for any stupid fool that can afford a pair of Kleins.
> 
> Lets dumb it down some more


I'm a new guy in the construction world (used to be a ballast changer ie maintenance guy) and we were pulling wires on 277 lights the other day and my JW told me to pull a GC for each circuit. I asked why can't we share the neutral he told me trade practice in my area is now to either pull a neutral (GC) for each leg or put handle ties between each phase so the maintenance guys don't get tickled on the unbalanced current coming back on the neutral.

Didn't get it 100% at the time but this thread is making it clearer. Thanks for all the good info posted.


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## zen (Jun 15, 2009)

Thanks for all replies. Maybe I should have just stated what im ginding. 15000 sq ft lease space no loads on any plug circuit. Its not occupied. Where here to use existing circuits to feed for new work stations (computers) tracing out circuits in LA2 NO multi pole breakers yet many are sharing neutrals so as we find them we add correct breaker. Then I came across ckt 6 and 28 are sharing a neutral . They were grouped together in a j box. Hard to breaker that. J box that fed this one had ckt 4 &6 grouped together sharing a neutral but ckt 4 was disconnected and 28 was used. 

learning to learn


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## zen (Jun 15, 2009)

I wanna find out what hots are sharing neutrals in a place with no loads. I feel lucky I found the circuits that changed which only makes me feel like I better know this new work is sound. All computer curcuits thats bad news if we mis something

learning to learn


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## zen (Jun 15, 2009)

Drawing of the circuit s

learning to learn


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## micromind (Aug 11, 2007)

4 and 28 cannot share a neutral, they are both B phase. The currents of both circuits will add and overload the neutral.

But if only one of them is being used with 6, it's ok.


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## zen (Jun 15, 2009)

Sorry my bad. Its 6 and 28. I dont like that it needs 2 pole breaker and I gotta rework the panel. Which will make all someone elses j box writing even more wrong. When I do rework a panel I write the date and what was done on the back of the panel cover

learning to learn


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## ponyboy (Nov 18, 2012)

I may be wrong but I don't think handle ties have always been required for mwbcs. If the installation is older it may have been up to code at time of installation


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## Bad Electrician (May 20, 2014)

Year_Zero said:


> I'm a new guy in the construction world (used to be a ballast changer ie maintenance guy) and we were pulling wires on 277 lights the other day and my JW told me to pull a GC for each circuit. I asked why can't we share the neutral he told me trade practice in my area is now to either pull a neutral (GC) for each leg or put handle ties between each phase so *the maintenance guys don't get tickled on the unbalanced current coming back on the neutral.*
> 
> Didn't get it 100% at the time but this thread is making it clearer. Thanks for all the good info posted.


But his explanation is WRONG, Two wire circuit ungrounded conductor and a grounded conductor open the neutral and grab that wire from the load and ground or the othher part of that open neutral and you will get knocked on your tushie.


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## power (Feb 27, 2012)

Simply put, yes, one neutral can be used in 3 phase systems. Each phase is 120deg displaced, therefore, neutral current is not cumulative. The neutral's ampacity would need to be determined by adding the phase current's vectorially as they are non-linear loads . 

However, the phases must be dissimilar! You are correct in saying that 2 similar phases sharing one neutral will result in potential heating. As was commented on, there are situations where switch-mode power supplies found in various equipment can produce harmonic currents flowing at frequency's above 60Hz, but, I am not suspecting you are inquiring about this. Easy way to check if you've goofed up: The neutral current should never be higher than the highest current on any of the individual 3 phases! 

If you are unsure and want to be "extra careful", I would suggest you over-rate the neutral by an AWG size or two (relative to phase conductor AWG size).

Hope this helps.


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## Bad Electrician (May 20, 2014)

power said:


> However, the phases must be dissimilar! You are correct in saying that 2 similar phases sharing one neutral will result in potential heating. As was commented on, there are situations where switch-mode power supplies found in various equipment can produce harmonic currents flowing at frequency's above 60Hz, but, I am not suspecting you are inquiring about this. Easy way to check if you've goofed up: The neutral current should never be higher than the highest current on any of the individual 3 phases!
> 
> 
> 
> Hope this helps.


If you are unsure amp all 3 phase conducts the current measured should match the neutral current for that MWBC


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## shwadaddy76 (Apr 28, 2013)

zen said:


> I started doing electrical work in 98 got a residential wiremans lisc in 2001. Then in 2005 tdlr or somebody grandfathered j cards I didnt think it was right so I passed on it. Then all the sudden im no longer getting good money or good jobs 2008 to the class for j test after the class I was told 2008 was only good for 1 more month. I didnt take the test. Stayed in resi till it bottomed out . Came to commercial. For 2.5 years and am learning its a whole new electrical world. Most of what I know comes from doing it. No schooling. Thanks that reply really helps
> 
> learning to learn


Glad you're finding ways to make your way in the trade. Keep lernin'


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## RIVETER (Sep 26, 2009)

zen said:


> Its common to see 3 hots per one neutral. It was explained to me this works because the ohases arent sharing the neutral at the same time. When we use 2 of the same phases they share it at the same time which is how they burn up. If anyone has time . Any good info on when its ok to share neutrals. Situations where it causes problems and trouble shooting tips to see its been done. Thanks
> 
> learning to learn


The phases...in fact are sharing the neutral at the same time.. What is going on is the fact that in three phase generation the peak currents average out because they are 120 degrees out of phase. That is to say that no individual phase reaches it's peak at the same time as the others.


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## RIVETER (Sep 26, 2009)

zen said:


> I wanna find out what hots are sharing neutrals in a place with no loads. I feel lucky I found the circuits that changed which only makes me feel like I better know this new work is sound. All computer curcuits thats bad news if we mis something
> 
> learning to learn


If you had circuit current flowing on the egcs could that cause wierd problems in computer equipment?


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## zen (Jun 15, 2009)

I have no idea. I would like to know

Sent from my SPH-D710BST using electriciantalk.com mobile app


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## RIVETER (Sep 26, 2009)

zen said:


> For what its worth. No I did not go to any school to be taught . The bottom line is I jacked around to long and other than on here the net and a code book. Thats all I got. Im a good employee never fryed ANYTHING ever. Never blasted any by being stupid or done anything that my boss or any customer have called to say wtf did he do. I dont do anything I dont know how to do. Being older than my supervisors means I may not get any real knowledge. So I learn where I can when I can. Thanks for any help I get.
> 
> learning to learn


Are you saying that your self esteem is where it should be?


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## zen (Jun 15, 2009)

I wouldnt say all that. I think I was summing up why I ask questions that are beyond my knowledge and that at times rubes those formally taught the wrong way. Its like im cheating to them.. if anything I wanted to make the point that I could have approached this field in a better way but I didnt and dont have a sob story to tell. My self esteem comes from knowing my son has a dad who is trying. Even though his lil butt wont go to bed and drives me crazy
View attachment 38679
View attachment 38679


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## Voltron (Sep 14, 2012)

zen said:


> I wouldnt say all that. I think I was summing up why I ask questions that are beyond my knowledge and that at times rubes those formally taught the wrong way. Its like im cheating to them.. if anything I wanted to make the point that I could have approached this field in a better way but I didnt and dont have a sob story to tell. My self esteem comes from knowing my son has a dad who is trying. Even though his lil butt wont go to bed and drives me crazy
> View attachment 38679
> View attachment 38679
> 
> ...


Do you want me to give you a price on adding a plug on that wall, so you can get rid of that taped up extension cord?


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## zen (Jun 15, 2009)

Thats coax.. 

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## B-Nabs (Jun 4, 2014)

Sorry to resurrect an old thread, but I just wanted to say: in Canada we share neutrals with non-sequential circuits all the time, multi-pole or handle tied breakers are only required where the two (or three) hot legs feed the same device, like a split receptacle or a multi-pole load (at least to my knowledge). So we'll have sets like 1-3-5 and 2-4-6, but if it's convenient to run something like 14-22-36 then we will, no problem. You just want to make sure your sets are well labelled throughout, and if you're working on or troubleshooting an energized system, DON'T OPEN THE NEUTRAL. Individual neutrals (which technically are not neutrals) are a waste of pipe, copper, larger junction boxes, time, panel space, etc. IMHO


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## Aegis (Mar 18, 2011)

It's amazing that we'll do this kind of stuff in Canada but then in the States they'll use different voltages in the same conduit.


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## B-Nabs (Jun 4, 2014)

That I did not know. That sounds scary.


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## Bad Electrician (May 20, 2014)

B-Nabs said:


> That I did not know. That sounds scary.


Maybe for amateurs, professionals take care in all work they perform.


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## RIVETER (Sep 26, 2009)

chicken steve said:


> Should we go down vector avenue?
> 
> ~CS~


I just entered on this thread. Why doesn't someone...YOU, talk about the generation of three phases electrical? AND, the fact that since the phases are generated 120 degrees apart the current on any phase will differ from the other phases of VOLTAGE?


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## Shockdoc (Mar 4, 2010)

I'm old school, I'm from the days of running one #8 neutral to 6 circuits in 3 ph systems. In fact I have been installing systems like this since the mid 90s . Have never come across any problems, don't know about any electricians after me who hopefully didn't disturb the monster.


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## Shockdoc (Mar 4, 2010)

Aegis said:


> It's amazing that we'll do this kind of stuff in Canada but then in the States they'll use different voltages in the same conduit.





B-Nabs said:


> Sorry to resurrect an old thread, but I just wanted to say: in Canada we share neutrals with non-sequential circuits all the time, multi-pole or handle tied breakers are only required where the two (or three) hot legs feed the same device, like a split receptacle or a multi-pole load (at least to my knowledge). So we'll have sets like 1-3-5 and 2-4-6, but if it's convenient to run something like 14-22-36 then we will, no problem. You just want to make sure your sets are well labelled throughout, and if you're working on or troubleshooting an energized system, DON'T OPEN THE NEUTRAL. Individual neutrals (which technically are not neutrals) are a waste of pipe, copper, larger junction boxes, time, panel space, etc. IMHO


This is the dumbing down of the US and its workforce. Too many idiots here who have no business in the business are in business. After they do something stupid like disturb a neutral on a multi wire branch without disconnecting hots first and frying stuff they blame the method instead of themselves. Americans are perfect.........so anything wrong they do is always something's fault.


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## B-Nabs (Jun 4, 2014)

I'm a relatively new journeyman, with lots left to learn, I will be the first to acknowledge that. But I take exception to the implication that I am an "amateur" for expressing surprise over something different from how we do things in my locality. And in my opinion, combining different voltages/systems in the same conduit sounds dangerous, never mind the fact that where I live it is not allowed. We can't even combine circuits of the same voltage that originate from differently derived systems (two panels side by side fed from different transformers cannot have their branch wiring run together). I come to this forum to learn of things I have not yet encountered, or to learn how to do things better and be a better electrician, not to be browbeaten and called an "amateur" or the like.


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## Aegis (Mar 18, 2011)

B-Nabs said:


> I'm a relatively new journeyman, with lots left to learn, I will be the first to acknowledge that. But I take exception to the implication that I am an "amateur" for expressing surprise over something different from how we do things in my locality. And in my opinion, combining different voltages/systems in the same conduit sounds dangerous, never mind the fact that where I live it is not allowed. We can't even combine circuits of the same voltage that originate from differently derived systems (two panels side by side fed from different transformers cannot have their branch wiring run together). I come to this forum to learn of things I have not yet encountered, or to learn how to do things better and be a better electrician, not to be browbeaten and called an "amateur" or the like.


Don't take offense. Us Canadians keep every voltage in separate conduits as you know. Even though Americans say 'well a professional didn't do this that's why', it's still not an organized way to run things IMO. The reality is that there are hacks out there who will do anything, I would prefer that the code (in any country) doesn't make it easier for these them. Unorganized electricians/hacks/maintenance guys will always touch equipment and turn it into a dogs breakfast, not always but a lot will. Because of this the whole multiple voltages in the same conduit makes it that much easier for them to crap all over an electricians work.

I've seen some pretty messed up stuff in Canada, I can't imagine the things going on in the states.


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## RIVETER (Sep 26, 2009)

B-Nabs said:


> I'm a relatively new journeyman, with lots left to learn, I will be the first to acknowledge that. But I take exception to the implication that I am an "amateur" for expressing surprise over something different from how we do things in my locality. And in my opinion, combining different voltages/systems in the same conduit sounds dangerous, never mind the fact that where I live it is not allowed. We can't even combine circuits of the same voltage that originate from differently derived systems (two panels side by side fed from different transformers cannot have their branch wiring run together). I come to this forum to learn of things I have not yet encountered, or to learn how to do things better and be a better electrician, not to be browbeaten and called an "amateur" or the like.


I have never heard of that method. However, it makes sense to me...more expensive...but sensible.:thumbsup:


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## Bad Electrician (May 20, 2014)

B-Nabs said:


> I'm a relatively new journeyman, with lots left to learn, I will be the first to acknowledge that. But I take exception to the implication that I am an "amateur" for expressing surprise over something different from how we do things in my locality. And in my opinion, combining different voltages/systems in the same conduit sounds dangerous, never mind the fact that where I live it is not allowed. We can't even combine circuits of the same voltage that originate from differently derived systems (two panels side by side fed from different transformers cannot have their branch wiring run together). I come to this forum to learn of things I have not yet encountered, or to learn how to do things better and be a better electrician, not to be browbeaten and called an "amateur" or the like.


If you feeling were bruised you may be in the wrong trade much less signed into the wrong forum. Things get tougher.

My point was and is we are use to it we expect it and know how to handle it. You per you code it seems are not exposed to this type of installation and would not expect to see it.

Did you know that there are 120 VAC and or 120 VDC circuits in 5KV, 13.8KV and higher voltage gear? How can that be? Because the people understand the systems and how to handle the equipment.


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## Meadow (Jan 14, 2011)

Bad Electrician said:


> If you feeling were bruised you may be in the wrong trade much less signed into the wrong forum. Things get tougher.
> 
> My point was and is we are use to it we expect it and know how to handle it. You per you code it seems are not exposed to this type of installation and would not expect to see it.
> 
> Did you know that there are 120 VAC and or 120 VDC circuits in 5KV, 13.8KV and higher voltage gear? How can that be? Because the people understand the systems and how to handle the equipment.


True but they are kept separate, all LV is run beside medium and high voltage conduit. But I agree, as BBQ said, if we had to consider idiots we would have to shut down the grid because said idiot can screw up a 2 wire lamp cord.

I get where the CEC comes from, neatness and quality is good (like bundling of MWBC) however the handle ties has nothing to do with that. More like keeping the hacks safe. :no:


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## Bad Electrician (May 20, 2014)

B-Nabs said:


> I'm a relatively new journeyman, with lots left to learn, I will be the first to acknowledge that. But I take exception to the implication that I am an "amateur" for expressing surprise over something different from how we do things in my locality. And in my opinion, combining different voltages/systems in the same conduit sounds dangerous, never mind the fact that where I live it is not allowed. We can't even combine circuits of the same voltage that originate from differently derived systems (two panels side by side fed from different transformers cannot have their branch wiring run together). I come to this forum to learn of things I have not yet encountered, or to learn how to do things better and be a better electrician, not to be browbeaten and called an "amateur" or the like.


It was not my intent to say you were an amateur though upon re-reading the thread I can see how you might think I was implying that.

My point was if you are good at what you do and know in advance the wiring methods in use you should be able to handle that situation. It is a matter of what you are use to and expect. I am sure in Canada if you ran into this it could be SHOCKING.

I believe sharing neutrals id fine I am not a fan of mixing voltages in the same conduit. Just my personal beliefs.


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## B-Nabs (Jun 4, 2014)

/butthurtedness


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## [email protected] (Jan 30, 2015)

*Oversized neutral*



FrunkSlammer said:


> Not sure your skill or knowledge level, but here's me making stuff up on the fly...
> 
> 3phase wye systems use a neutral.. the 3 hots make up a full rotation of a generator at the power plant. 1 hot will make up 1/3rd of that rotation.
> 
> ...


In theatrical environments an oversized neutral is required in a three phase environment - lot of harmonics across the dimmers - This is evident when metering the tree phases and the neutral between two lighting cues (know as a cross fade) - the neutral can exceed the phase current. When all lamps are balanced (rarely) and at full power, the neutral goes to zero.

Our first electrician did not appreciate theater electrical requirements and had #6 feeders and insisted on a #10 neutral which burned up after a few shows. The new electrician replaced this with #4.


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## McClary’s Electrical (Feb 21, 2009)

[email protected] said:


> In theatrical environments an oversized neutral is required in a three phase environment - lot of harmonics across the dimmers - This is evident when metering the tree phases and the neutral between two lighting cues (know as a cross fade) - the neutral can exceed the phase current. When all lamps are balanced (rarely) and at full power, the neutral goes to zero.
> 
> Our first electrician did not appreciate theater electrical requirements and had #6 feeders and insisted on a #10 neutral which burned up after a few shows. The new electrician replaced this with #4.


Paging mx slick. Paging eddrick..... paging mx slick, paging eddrick


True or false?


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## MTW (Aug 28, 2013)

Aegis said:


> Don't take offense. Us Canadians keep every voltage in separate conduits as you know. Even though Americans say 'well a professional didn't do this that's why', it's still not an organized way to run things IMO. The reality is that there are hacks out there who will do anything, I would prefer that the code (in any country) doesn't make it easier for these them. Unorganized electricians/hacks/maintenance guys will always touch equipment and turn it into a dogs breakfast, not always but a lot will. Because of this the whole multiple voltages in the same conduit makes it that much easier for them to crap all over an electricians work.
> 
> I've seen some pretty messed up stuff in Canada, I can't imagine the things going on in the states.



But, you have to requirement to identify conductors by phase and system, whereas we do. You have black/red/blue for everything, whereas we use almost every color of the rainbow. We require phase/system identification, you require physical separation. In a perfect world, they accomplish the same end.


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## Bad Electrician (May 20, 2014)

meadow said:


> True but they are kept separate, all LV is run beside medium and high voltage conduit. But I agree, as BBQ said, if we had to consider idiots we would have to shut down the grid because said idiot can screw up a 2 wire lamp cord.
> 
> I get where the CEC comes from, neatness and quality is good (like bundling of MWBC) however the handle ties has nothing to do with that. More like keeping the hacks safe. :no:


Not inside the transformer.


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## guest (Feb 21, 2009)

[email protected] said:


> In theatrical environments an *oversized neutral is required in a three phase environment - lot of harmonics across the dimmers *- This is evident when metering the tree phases and the neutral between two lighting cues (know as a cross fade) - *the neutral can exceed the phase current.* When all lamps are balanced (rarely) and at full power, the neutral goes to zero.
> 
> Our first electrician *did not appreciate theater electrical requirements and had #6 feeders and insisted on a #10 neutral which burned up after a few shows. The new electrician replaced this with #4.*





mcclary's electrical said:


> Paging mx slick. Paging eddrick..... paging mx slick, paging eddrick
> 
> 
> *True* or false?



Absolutely true. Theatrical dimmers are brutal in how the chop the AC waveform to accomplish the dimming..resulting in all kinds of harmonics AND current/voltage "offsets" at the peaks....which wreaks havoc on the neutral currents. 

It also creates a very hostile RF/EMF noise environment for audio gear. (Even in single phase applications). (To prove that, try using an AM radio in a theatrical venue with the dimming system operating... good luck getting anything other than a LOT of grating noise and static.)

200% Neutrals and "K" rated transformers are a good idea even in small theatrical venues, and mandatory in large venues to avoid equipment failures. 

And speaking of audio gear, shared neutrals are a very bad idea for audio equipment circuits, especially since a lot of modern amplifiers and signal processing gear uses switch-mode power supplies which generate harmonics on their own.


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## cabletie (Feb 12, 2011)

We have done theaters in the past. Most just in schools. On large private theater had a different setup for audio circuits. It had a single phase panel, one phase one neutral. Never saw a panel like it before or since. 

I would imagine it is always a good idea to keep your audio circuits on the same phase? Even without a fancy panel


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## Rollie73 (Sep 19, 2010)

mxslick said:


> Absolutely true. Theatrical dimmers are brutal in how the chop the AC waveform to accomplish the dimming..resulting in all kinds of harmonics AND current/voltage "offsets" at the peaks....which wreaks havoc on the neutral currents.
> 
> It also creates a very hostile RF/EMF noise environment for audio gear. (Even in single phase applications). (To prove that, try using an AM radio in a theatrical venue with the dimming system operating... good luck getting anything other than a LOT of grating noise and static.)
> 
> ...


 
Thanks mx......I bid a job a while back (didn't get it) in a local theatre. Movie theatres in one side and live stages on the other side with huge mounts of lighting and dimming panels everywhere.

The entire job was spec'd for K rated transformers and the neutrals on the main feeders at the lighting panels were 3x the size of the ungrounded conductors. I _think _I recall it being designed for dedicated neutrals in the sound rooms but could be wrong on that.

Your explanation makes it a bit clearer why the engineer had it designed this way.


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## guest (Feb 21, 2009)

cabletie said:


> We have done theaters in the past. Most just in schools. On large private theater had a different setup for audio circuits. It had a single phase panel, one phase one neutral. Never saw a panel like it before or since.
> 
> *I would imagine it is always a good idea to keep your audio circuits on the same phase?* Even without a fancy panel


Well, the answer is yes..and no. :laughing:

Industry practice has always recommended keeping all of the audio gear, _*including the amplifiers*_, on the same phase. 

The real-world however, finds that keeping everything, especially the amplifiers, on the same phase can introduce other problems unrelated to the actual audio quality.... things like unbalanced feeder loading, and rare (but has happened) things like a single amplifier catastrophic failure causing voltage disturbances bad enough to damage other, unrelated equipment. (One theatre I used to service lost ALL of the speakers in such a fault...the induced noise and spikes from the one amplifier that smoked made the others unstable enough to blow out the speakers.) 

A properly wired and grounded audio system can readily spread the load across two or more phases without any noise issues. For example, in my average cinema racks, I have one circuit for ALL of the "line-level" (before the amplifiers) gear on one circuit, and 8 or more amplifiers divided two per circuit over as many circuits as needed, balancing the remaining phases of the panel as much as possible. All circuits do have *dedicated neutrals, *one grounding conductor for the entire rack, and one #6 technical ground attached directly to the equipment rack and sent to the panel's grounding bus bar. No isolated grounds..waste of time and money. 

The real trick to a good audio system is to make sure all of your "line-level" wiring is routed properly (as far away from, and NEVER running in parallel with) the AC cords or speaker lines. Use of "single-ended" or "telescoping" shields as necessary. (That is a an art in itself, figuring out when to do that.) 

Out of the hundreds of cinemas and home screening rooms I have done, there have been NO issues on either the AC power or audio quality sides as long as my specs were followed. :thumbsup:


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## five.five-six (Apr 9, 2013)

Would that not have to assume the same power factor on each phase?





Bad Electrician said:


> No look at the math and calculate for "0" amps on any one phase.
> 
> In the statement below (v) should have been the square root symbol
> 
> ...


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## five.five-six (Apr 9, 2013)

mxslick said:


> The real trick to a good audio system is to make sure all of your "line-level" wiring is routed properly (as far away from, and NEVER running in parallel with) the AC cords or speaker lines. Use of "single-ended" or "telescoping" shields as necessary. (That is a an art in itself, figuring out when to do that.)
> 
> Out of the hundreds of cinemas and home screening rooms I have done, there have been NO issues on either the AC power or audio quality sides as long as my specs were followed. :thumbsup:



The most common problem that I have seen is from a voltage differential in chaises, and current passing across the interconnects. If you have ever eliminated noise by inserting a type F isolation transformer on the cable service, that's the problem that you had. 

I think that the theory behind keeping everything on the same phase or leg was to eliminate potential between chassis, but proper grounding will do a better job of that.


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