# Same Phase in Same Condiut?



## Pete m. (Nov 19, 2011)

As long as each has it's own neutral, yes.

Pete


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## electric_mayhem (Apr 27, 2012)

Why not? As long as you don't exceed the conduit fill and derate if needed there is no problem. Just don't share the neutral and provide means of identifying which hot and neutral go together. The last time I had to put 2 "A" phase conductors in the same conduit I oversized one circuit from #12 to #10. This makes it much more helper proof.


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## travis13 (Oct 12, 2012)

So as long as each hot conductor has its own neutral it is ok? I guess in my head I was thinking that since the hot conductors were on the same sine wave then it would create more heat. Could you please explain why the separate neutrals make a difference. Thanks!


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## electric_mayhem (Apr 27, 2012)

3 phases are out of sync...the neutral can sustain the current of all three out of sync phases. Put 2 synchronized phases on 1 neutral and it will be overloaded, creating heat. If each synchronized phase has it's own neutral no overload, no heat, all good. The heat you are worried about would occur if you exceed your conduit fill or you fail to derate if needed. Good luck


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## 480sparky (Sep 20, 2007)

Sreed24 said:


> ...... Put 2 synchronized phases on 1 neutral and it will create the potential to be overloaded, creating heat........


Fify.


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## travis13 (Oct 12, 2012)

So it really has nothing to do with the hot conductors, it's all about them being on a dedicated neutral. This forum is awesome. I'm a second year apprentice and a lot of times I can't get these questions answered


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

I just want to clarify, you kept saying each one has a dedicated neutral, but you could have 6 hots and two neutrals in the conduit, as long as they're phased correctly.


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## Jhellwig (Jun 18, 2014)

You could have 304 sets of hots and neutral in one conduit on the same phase if you so wished.


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## travis13 (Oct 12, 2012)

Let me add another scenario here: Let's say you are running two parallel runs of 500 to a motor. Someone decides to run three conduits to the motor. One conduit for each like phase. Since there is no neutral, what would that do? I know this situation is very impractical, just seeing if this changes things.


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## travis13 (Oct 12, 2012)

Jhellwig said:


> You could have 304 sets of hots and neutral in one conduit on the same phase if you so wished.


Ok that is confusing me a little


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## B-Nabs (Jun 4, 2014)

Jhellwig said:


> You could have 304 sets of hots and neutral in one conduit on the same phase if you so wished.


Not in Canada you couldn't; we are allowed a maximum of 200 conductors in a pipe. (not saying that OP is Canadian, just saying for interest's sake).



travis13 said:


> Let me add another scenario here: Let's say you are running two parallel runs of 500 to a motor. Someone decides to run three conduits to the motor. One conduit for each like phase. Since there is no neutral, what would that do? I know this situation is very impractical, just seeing if this changes things.


Correct me anyone if I'm wrong, but parallel runs are supposed to be grouped so that all phases (and neutral if present) are contained in the same raceway (that is to say, one set of ABC in one pipe and the other set in another pipe). That way the phases all cancel each other and don't create as strong a magnetic field, leading to induced current and heat in the pipe (assuming the pipe is metal).


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## travis13 (Oct 12, 2012)

The magnetic field created by like conductors is what I should have asked originally. I was told that if like phases were in the same conduit then it would create heat/resistance therefore raising the current.


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## B-Nabs (Jun 4, 2014)

travis13 said:


> The magnetic field created by like conductors is what I should have asked originally. I was told that if like phases were in the same conduit then it would create heat/resistance therefore raising the current.


In your original question, because the two circuits each have their own neutral, the current on each hot and its respective neutral cancel each other. In the second scenario with the parallel runs, you have two A's in the first pipe, two B's in the second, and two C's in the third; the currents are in the same direction, so they don't cancel. This is where you get induction on a metal raceway. If A, B, and C were in the same pipe (so you only use two of the pipes), then their currents cancel each other because they have equal phase displacement, thus avoiding the induction to the pipe.


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## Jhellwig (Jun 18, 2014)

travis13 said:


> Ok that is confusing me a little


. You could have 304 circuits each with their own neutrals in one conduit if you pleased and be code compliant.



B-Nabs said:


> Not in Canada you couldn't; we are allowed a maximum of 200 conductors in a pipe. (not saying that OP is Canadian, just saying for interest's sake)


I just took the most 14 guge wires you could put into 4" emt. We don't have a number of conductor limit that I know of. That many in wires in a conduit would in to way be practical even for control circuits.



travis13 said:


> The magnetic field created by like conductors is what I should have asked originally. I was told that if like phases were in the same conduit then it would create heat/resistance therefore raising the current.


The magnetic fields of the hots and neutrals cancel each other out. The amount of amps going out on the hot are 180 degrees out of the amps coming back on its neutral. That causes the effective magnetic field of the two wires to cancel each other. No matter how many sets of wires you have they cancel each other out. That is the reason you have to put the hot and neutral in the same raceway or cable. You will still have resistive heating and the more circuits the more heat. That is the reason for the derating with more than 3 current carrying conductors.


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## Jhellwig (Jun 18, 2014)

You can get a good feel of how this works with a clamp meter. Take two separate wires and hook them up to a load. Power it up and take an amp reading on each wire then read both wires at the same time. The current you see on both wires will be you current that will cause any inductive heating(hint, there won't be any current reading).

You could go further with it and loop the wire through the clamp a few times or fold the wire over in the middle and stick it in the meter. It will help explain several things.


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## travis13 (Oct 12, 2012)

JHellwig, with the 304 circuits, would they have to be within 24" of the device...etc, or would have to be dramatically derated to be code compliant?


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

B-Nabs said:


> Not in Canada you couldn't; we are allowed a maximum of 200 conductors in a pipe. (not saying that OP is Canadian, just saying for interest's sake).
> 
> 
> 
> Correct me anyone if I'm wrong, but parallel runs are supposed to be grouped so that all phases (and neutral if present) are contained in the same raceway (that is to say, one set of ABC in one pipe and the other set in another pipe). That way the phases all cancel each other and don't create as strong a magnetic field, leading to induced current and heat in the pipe (assuming the pipe is metal).


There is an exception that allows you to run all the a phases in one conduit, ask the b in another, and c in a third, but the conduits must be underground and non metallic.


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## Fibes (Feb 18, 2010)

Jhellwig said:


> The magnetic fields of the hots and neutrals cancel each other out.


The same is true of hots and associated switch legs. 

The bottom line is, if a circuits current is flowing in opposite directions in close proximity to each other the EMF is negated.


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## B-Nabs (Jun 4, 2014)

mcclary's electrical said:


> There is an exception that allows you to run all the a phases in one conduit, ask the b in another, and c in a third, but the conduits must be underground and non metallic.



And would you be required to use non-ferrous lock rings in that scenario?



Sent from my iPhone using Tapatalk


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## Pete m. (Nov 19, 2011)

B-Nabs said:


> And would you be required to use non-ferrous lock rings in that scenario?
> 
> 
> 
> Sent from my iPhone using Tapatalk


Yes.

Pete


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## Fibes (Feb 18, 2010)

mcclary's electrical said:


> There is an exception that allows you to run all the a phases in one conduit, ask the b in another, and c in a third, but the conduits must be underground and non metallic.


 
That would be the exception to 300.3(B)(1) and takes you to 300.20(B)


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## 480sparky (Sep 20, 2007)

FYI: you're not limited to conduit (round tubes) when theorizing about huge numbers of CCCs. You can get gutters large enough to stuff hundreds of conductors in.


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## cabletie (Feb 12, 2011)

B-Nabs said:


> mcclary's electrical said:
> 
> 
> > There is an exception that allows you to run all the a phases in one conduit, ask the b in another, and c in a third, but the conduits must be underground and non metallic.
> ...


In most cases the conduit would have PVC bell ends on them. The conduit would stub up into open bottom enclosures, switchgear or utility transformers


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## cabletie (Feb 12, 2011)

480sparky said:


> FYI: you're not limited to conduit (round tubes) when theorizing about huge numbers of CCCs. You can get gutters large enough to stuff hundreds of conductors in.



But wireways and auxiliary gutters are also subject to de rating after 30 current conductors


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## 480sparky (Sep 20, 2007)

cabletie said:


> But wireways and auxiliary gutters are also subject to de rating after 30 current conductors


Were discussing theoretical raceway fills of epic proportions, not derating.


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## don_resqcapt19 (Jul 18, 2010)

mcclary's electrical said:


> There is an exception that allows you to run all the a phases in one conduit, ask the b in another, and c in a third, but the conduits must be underground and non metallic.


While the CMP does not agree with me, I see no need for that exception. It is my opinion that 300.3(B)(3) permits an "isolated phase" installation in all locations.


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## Meadow (Jan 14, 2011)

All current carrying conductors of an individual branch circuit must be within the same conduit or raceway.


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## Fibes (Feb 18, 2010)

meadow said:


> All current carrying conductors of an individual branch circuit must be within the same conduit or raceway.


Not always, see the aforementioned 300.3(B)


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> All current carrying conductors of an individual branch circuit must be within the same conduit or raceway.


The main part of 300.3(B) says that but also goes on to say "unless otherwise permitted in 300.3(B)(1) through 300.3(B)(4). The (1) through (4) subsections act as exceptions to the main rule.


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## Jhellwig (Jun 18, 2014)

travis13 said:


> JHellwig, with the 304 circuits, would they have to be within 24" of the device...etc, or would have to be dramatically derated to be code compliant?


There are situations where you wouldn't be restricted to those rules. Don't get confused by it though, it was just an example to illustrate the point.

In the situation you asked about in you first post it is not a matter of the two circuits being on the same phase. They could be on different phases and the same rules would apply. 

Now if you were to to turn you two circuits into a multi wire brach circuit then you would only have two current carrying conductors in the raceway instead of four all while only having one less wire. If you added two more circuits with separate neutrals you would have 8 current carrying conductors yet if you changed it to two multi wire branch circuits you would only have four ccc yet you only remove two wires from the conduit. Not that this only applies to non wye systems.


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## Meadow (Jan 14, 2011)

Fibes said:


> Not always, see the aforementioned 300.3(B)





don_resqcapt19 said:


> The main part of 300.3(B) says that but also goes on to say "unless otherwise permitted in 300.3(B)(1) through 300.3(B)(4). The (1) through (4) subsections act as exceptions to the main rule.


But that would only apply to romex or paralleled conductor sets in none ferro conduit?

My understanding is that if this is a 14-10 gauge general branch circuit it is never allowed?


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## B-Nabs (Jun 4, 2014)

Jhellwig said:


> Now if you were to to turn you two circuits into a multi wire brach circuit then you would only have two current carrying conductors in the raceway instead of four all while only having one less wire.


Unless we're talking about a 3-phase system, in which case two hots sharing a neutral would be three current carrying conductors, would it not? Because (assuming both hots carry full rated current) the neutral carries the same amount of current as the two hots, dunnit?


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## Jhellwig (Jun 18, 2014)

B-Nabs said:


> Unless we're talking about a 3-phase system, in which case two hots sharing a neutral would be three current carrying conductors, would it not? Because (assuming both hots carry full rated current) the neutral carries the same amount of current as the two hots, dunnit?


That would be why I said it only applies to non wye systems. The neutral in a mwbc derived from from a delta system is not a current carrying conductor. Only in a wye derived system. 

On a wye system the neutral carries the average current as the phases even if you are only using two of the phases.


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## don_resqcapt19 (Jul 18, 2010)

meadow said:


> But that would only apply to romex or paralleled conductor sets in none ferro conduit?


It applies as written, however I disagree with code making panel as to the meaning of some parts of these sections.


> My understanding is that if this is a 14-10 gauge general branch circuit it is never allowed?


What is never allowed?


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## B-Nabs (Jun 4, 2014)

Jhellwig said:


> That would be why I said it only applies to non wye systems. The neutral in a mwbc derived from from a delta system is not a current carrying conductor. Only in a wye derived system.
> 
> On a wye system the neutral carries the average current as the phases even if you are only using two of the phases.


So you did, my mistake.


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