# Sub feeders split into two conduits?



## Blayney86 (Jan 18, 2013)

I remember back in the day with one of my old bosses he tried to do this cause he was recycling old flex and the inspector called him on it. I've never had a need to do this before now. I have a project in a large building that needs a 200 amp sub 225' from the electrical room. There are some extra 2" conduits underground going from the electrical room to a location very close to where I need to be. I will be running 4/0 3 phase which will not fit in the 2" that's there, and would like to split it into two conduits. Is there actually somewhere in the book that prohibits this?


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## manchestersparky (Mar 25, 2007)

Metallic or Non-Metallic Conduits?
From the 2014 NEC:

300.20 Induced Currents in Ferrous Metal Enclosures or Ferrous Metal Raceways
(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in ferrous metal enclosures or ferrous metal raceways, they shall be arranged so as to avoid heating the surrounding ferrous metal by induction. To accomplish this, all phase conductors and, where used, the
grounded conductor and all equipment grounding conductors shall be grouped together.

Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin effect heating in accordance with the provisions of 426.42 and 427.47.


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## Blayney86 (Jan 18, 2013)

Thanks hadn't thought about doing this before so wasn't sure where to look. And its EMT.


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## don_resqcapt19 (Jul 18, 2010)

Four 4/0 THWNs fit in 2" EMT.

300.3(B) would be another code section that says you can't split the conductors of the same circuit into multiple raceways.


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## RIVETER (Sep 26, 2009)

Blayney86 said:


> I remember back in the day with one of my old bosses he tried to do this cause he was recycling old flex and the inspector called him on it. I've never had a need to do this before now. I have a project in a large building that needs a 200 amp sub 225' from the electrical room. There are some extra 2" conduits underground going from the electrical room to a location very close to where I need to be. I will be running 4/0 3 phase which will not fit in the 2" that's there, and would like to split it into two conduits. Is there actually somewhere in the book that prohibits this?


Why not bid the job as a new one using new materials. Why would you care if it takes longer? A person could use a 40 year old conduit and two weeks later it shears and cuts the cables and you will be responsible. Bid it as NEW.


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## ponyboy (Nov 18, 2012)

(4) 4/0s will fit in a 2" but it's a jam fest. Why not use 3/0s which are good for 200 amp?


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## Blayney86 (Jan 18, 2013)

ponyboy said:


> (4) 4/0s will fit in a 2" but it's a jam fest. Why not use 3/0s which are good for 200 amp?


 
First off I have a ground as well. But im running 4/0 to avoid voltage drop since its a 220' run.


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## Blayney86 (Jan 18, 2013)

RIVETER said:


> Why not bid the job as a new one using new materials. Why would you care if it takes longer? A person could use a 40 year old conduit and two weeks later it shears and cuts the cables and you will be responsible. Bid it as NEW.


 
I see your point. Though it is a university that is one of my main sources of work so I try and save them money if I can. I am also insanely busy right now so im not trying to extend jobs haha It is only a 8yr old building so I don't really have to worry about the bad pipes.


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## ponyboy (Nov 18, 2012)

Blayney86 said:


> First off I have a ground as well. But im running 4/0 to avoid voltage drop since its a 220' run.


Is that based on a load calculation and a voltage drop calculation? Just asking because it seems sometimes people just assume they need to upsize when they might not actually need to.


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## Blayney86 (Jan 18, 2013)

So now im thinking about parallel 1/0 since that's the smallest you can do that with. And avoid running 200' of EMT through numerous different rooms.


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## Blayney86 (Jan 18, 2013)

ponyboy said:


> Is that based on a load calculation and a voltage drop calculation? Just asking because it seems sometimes people just assume they need to upsize when they might not actually need to.


 
Yeah we'll be loading up this panel to 75% of its max. And did do a voltage drop calc. So I don't wanna loose more than 3%


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## ponyboy (Nov 18, 2012)

Compact conductors maybe?


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## Southeast Power (Jan 18, 2009)

Blayney86 said:


> I remember back in the day with one of my old bosses he tried to do this cause he was recycling old flex and the inspector called him on it. I've never had a need to do this before now. I have a project in a large building that needs a 200 amp sub 225' from the electrical room. There are some extra 2" conduits underground going from the electrical room to a location very close to where I need to be. I will be running 4/0 3 phase which will not fit in the 2" that's there, and would like to split it into two conduits. Is there actually somewhere in the book that prohibits this?


I see parallel runs all of the time.
What seems to be the problem?


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## Dennis Alwon (May 9, 2009)

I think the use of parallel 1/0 is a good way to go. BTW you technically don't need an equipment grounding conductor since the emt would be compliant. The problem is knowing the integrity of the run.


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## Dennis Alwon (May 9, 2009)

Also if you upsize the conductors then you must upsize the equipment grounding conductor proportionally--250.122(B)


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## theJcK (Aug 7, 2013)

Dennis Alwon said:


> I think the use of parallel 1/0 is a good way to go. BTW you technically don't need an equipment grounding conductor since the emt would be compliant. The problem is knowing the integrity of the run.


what would be the best method of testing this?..


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## Dennis Alwon (May 9, 2009)

theJcK said:


> what would be the best method of testing this?..


Good question. Not sure perhaps a mega meter or maybe just an ohm meter-- never had to do it so I am not sure what would work better. Brian (bad electrician) would probably know.


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## manchestersparky (Mar 25, 2007)

don_resqcapt19 said:


> Four 4/0 THWNs fit in 2" EMT.
> 
> 300.3(B) would be another code section that says you can't split the conductors of the same circuit into multiple raceways.


300.3 (B)

(B) Conductors of the Same Circuit.
All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).


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## Jhellwig (Jun 18, 2014)

Dennis Alwon said:


> I think the use of parallel 1/0 is a good way to go. BTW you technically don't need an equipment grounding conductor since the emt would be compliant. The problem is knowing the integrity of the run.


This. 

If you have two conduits that take the same path, parallel it. if you lugs in your panel won't take two writes you might have to unparallel it before going into the panel.


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## Blayney86 (Jan 18, 2013)

Thanks guys yeah I have a ton of 2" runs going there already but they do go underground and then through different parts of this building so I planned on running the ground just to be on the safe side. I'm definitely gonna go the parallel 1/0 route


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## Achilles (Sep 11, 2014)

ponyboy said:


> Is that based on a load calculation and a voltage drop calculation? Just asking because it seems sometimes people just assume they need to upsize when they might not actually need to.


Agreed -Without knowing the voltage/load I took worse case scenario.

208V 3Ph 225' @ 180A = 2.96% voltage drop using 3/0.

Seems like a safe bet to stick with 3/0 cu. Cheaper and less labor then parallel 1/0.


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