# How many current carrying conductors in conduit?



## JasonCo

I know this question has been asked a million times, but for the life of me I can't find out how to calculate how many current carrying conductors in a pipe that's existing. For example, at work I have a 1 inch emt and i want to know how many current carrying conductors I can put in the pipe. 

When I search online, all i get is the answer without actual explanations! 

So if I have a 1 inch emt, how do I solve how many #12 conductors can I fit in the pipe? 

Using my phone to post this for the first time, so bare with me! This is not easy!


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## ponyboy

Your question is too vague. Are you looking for pipe fill or derating requirements? Derating requirements are the same regardless of pipe size. Table 310.15(B)(3)(a)


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## RePhase277

Look at the tables in Chapter 9. Find the cross-sectional area of 1 inch EMT at 40% fill. Now find the cross-sectional area of an insulated #12. Divide the former by the latter to get what you're looking for.

Then the ampacity of each conductor is derated by table 310.15(B)(3)(a) according to the number of current carrying conductors.


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## frenchelectrican

Hey Ponyboy and Rephase277 .,

How come you guys posted two different NEC codes on the derating and fill in the table ? 

320.15(B)(3)(a)

Or 

310.15(B)(3)(a)

I am aware there is two different NEC code cycle it may shifted the location some but I just want to make sure we are on the right spot on the table. 

JasonCo.

Both guys posted a very good NEC table to look up and there is a difference on the derating and fill tables.


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## ponyboy

frenchelectrican said:


> Hey Ponyboy and Rephase277 .,
> 
> 
> 
> How come you guys posted two different NEC codes on the derating and fill in the table ?
> 
> 
> 
> 320.15(B)(3)(a)
> 
> 
> 
> Or
> 
> 
> 
> 310.15(B)(3)(a)
> 
> 
> 
> I am aware there is two different NEC code cycle it may shifted the location some but I just want to make sure we are on the right spot on the table.
> 
> 
> 
> JasonCo.
> 
> 
> 
> Both guys posted a very good NEC table to look up and there is a difference on the derating and fill tables.




Sorry, mine was a typo. The article is 310 not 320


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## JasonCo

Sorry for the late response! I had to post this while at work, pulled a double shift today and now its 1 in the morning. Going to read over all of this and then respond when I get up. Just wanted to thank everyone for your post before heading off to sleep :sleep1:

Edit:


ponyboy said:


> Your question is too vague. Are you looking for pipe fill or derating requirements? Derating requirements are the same regardless of pipe size. Table 310.15(B)(3)(a)
> 
> 
> Sent from my iPhone using Tapatalk


I'm also a bit confused on my own question then. I'm just trying to figure out how many current carrying conductors can go in a 1 inch emt for example. Lets assume the emt is ran inside a building with normal temperatures. I'm not looking to do anything like voltage drop and what not. Don't you always have to derate when figuring out how many current carrying conductors you can put in a 1 inch emt? Idk, I'm a bit confused honestly with all this. But I'm defiantly wanting to know about pipe fill I think :wallbash:.. I'm so warn out and tired I can't even think straight right now.


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## telsa

JasonCo said:


> Sorry for the late response! I had to post this while at work, pulled a double shift today and now its 1 in the morning. Going to read over all of this and then respond when I get up. Just wanted to thank everyone for your post before heading off to sleep :sleep1:
> 
> Edit:
> 
> 
> I'm also a bit confused on my own question then. I'm just trying to figure out how many current carrying conductors can go in a 1 inch emt for example. Lets assume the emt is ran inside a building with normal temperatures. I'm not looking to do anything like voltage drop and what not. Don't you always have to derate when figuring out how many current carrying conductors you can put in a 1 inch emt? Idk, I'm a bit confused honestly with all this. But I'm defiantly wanting to know about pipe fill I think :wallbash:.. I'm so warn out and tired I can't even think straight right now.


Homework should be run by your foreman// lead man first. :devil3:


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## Helmut

JasonCo said:


> I'm just trying to figure out how many current carrying conductors can go in a 1 inch emt for example.


You're going about this wrong.

You can fit one CCC (current carrying conductor) in a 1" EMT, or you fit 20.

It depends on the wire size, and the derating of conductors that you need to worry about.


The question you posted, is not answerable, with the data you provided.


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## ponyboy

JasonCo said:


> Sorry for the late response! I had to post this while at work, pulled a double shift today and now its 1 in the morning. Going to read over all of this and then respond when I get up. Just wanted to thank everyone for your post before heading off to sleep :sleep1:
> 
> 
> 
> Edit:
> 
> 
> 
> 
> 
> I'm also a bit confused on my own question then. I'm just trying to figure out how many current carrying conductors can go in a 1 inch emt for example. Lets assume the emt is ran inside a building with normal temperatures. I'm not looking to do anything like voltage drop and what not. Don't you always have to derate when figuring out how many current carrying conductors you can put in a 1 inch emt? Idk, I'm a bit confused honestly with all this. But I'm defiantly wanting to know about pipe fill I think :wallbash:.. I'm so warn out and tired I can't even think straight right now.




Look at the table I referenced earlier, it shows you exactly how many current carrying conductors are allowed before further derating. 


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## Bird dog

Pipe fill & number of current carrying conductors are two separate questions. Number of CCCs has no bearing on pipe fill because the derate is the same whether you are pulling #12s in 1" or 6" for example.


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## tjb

1” EMT - you want to know how many #12AWG CCCs you can run in it before you have to derate them to a #10AWG. Is that correct? So it’s not just a matter of looking at one table. 

First, go to Annex C. Table C1 is for EMT, and tells you EXACTLY how many CCCs you can run in a given trade size EMT. Find your insulation on the left column (THHN, XHHW, THWN, whatever). Next column, find your conductor size (#12AWG). Now find your EMT trade size column (1” in your case). If you’re running THHN for example, you can have 26 in there. 

Of course, it doesn’t end there. Table 310.15(b)(3)(a) now has to be applied, because you have more than three CCCs in that conduit (assuming it’s more than 24” long, per 310.15(b)(3)(a)(2)). So now your conductors can only carry 45% of the ampacity otherwise allowable for your situation in table 310.15(b)(16) (in this case 13.5A (30x.45)). 

Now you also must apply any other adjustments required by your particular installation. High ambient temperature (310.15(b)(2)(a)), or pipe run on a roof that will be in sunlight (310.15(b)(3)(c)), or voltage drop due to length of run (210.19(a)(info 4)), blah blah blah. 

Based on any of that, you may need to upsize your conductors because of those derating factors, maybe to a #10 or #8 (so maybe now you need a second pipe run, or a bigger pipe. Second run is almost always easier and cheaper in my experience). 

And that’s only if all the wires you’re putting in the pipe are the same size. There’s a different method if they’re not the same size. 

You have to know this stuff! This is part of your job!

(Of course I probably said something incorrect in there, and now everyone is going to yell at me to know MY job! Bwahaha)


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## JasonCo

telsa said:


> Homework should be run by your foreman// lead man first. :devil3:


This is not a homework question, this is a situation that I ran across in the field and just out of curiosity I'd like to know how to solve it. Why assume this is homework!!! :vs_mad: 

Edit: By the way, I'm the only person in my entire school that has to pay for his schooling. Every other person in my school has their schooling payed for by their company. I am legit 100% the only kid, so if I do have a homework question, it's because I also want to understand it and not just know the answer. I'm in school because I want to learn, I could care less about just posting a question online to get the answer to a question. Schooling doesn't get me a J Card, 8000 hours gets me a J Card. I would of dropped out of school 3 years ago like 70% of the kids already if I was just in school because of my company put me in it. I got in on my own will, had nothing to do with my company. Just wanted to get this off my chest

1:30pm and finally woke up, feeling a bit grumpy so I'm sorry lol. Giving this thread a good read now! Thanks a ton for the responses


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## frenchelectrican

JasonCo said:


> This is not a homework question, this is a situation that I ran across in the field and just out of curiosity I'd like to know how to solve it... Why assume this is homework :vs_mad:


If you are in the trade long enough., you should able know this by now.

That was one of few thing I learn it when I start working long time ago so I teach my guys to make sure they are aware of derating and conductor fill. 

I know it complety two diffrent things but you have to understand both to get it working smooth. 

I Do the review on derating and conductor fill from time to time to keep it fresh. especially if you doing alot of conduit runs.

Belive or not the derating do affect the NM cables as well.


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## Bird dog

JasonCo said:


> This is not a homework question, this is a situation that I ran across in the field and just out of curiosity I'd like to know how to solve it... Why assume this is homework :vs_mad:


Because it sounds like homework question. What was the situation? Did you have to add a ckt? The answer is 1) Can you physically pull the new wires into the pipe--pipe fill, 2) At what point does your derate on the #12s drop below 20amps (for the OCPD) that you have to repull everything using #10s? Then check pipe fill again because all those #10s may not fit. :vs_laugh:


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## macmikeman

Not necessarily in order of importance:

Pipe fill from the appendix in the NEC at the back Ch 9

Ambient temperature

Insulation type

Are the conductors running across a rooftop?

Derate according to number of wires in that conduit.

If this is all serving ac motors with those hermetically sealed compressors with the overload bimetal interrupter's built in to them? (may affect de-rating a bit depending on wire type and size. )

Lastly and not really required by code but rather by common sense- voltage drop. (You want the stuff to work correctly right? And get paid right?)


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## Eddie702

The # of conductors you can put in a pipe = the maximum # of that size wire that you can pull in and not be over 40% fill.

Then, if you have more than 3 cc conductors you have to derate the wire ampacity based on how many cc conductors you actually have. You also may have to derate for ambient temperature as well.

If because of derating you have to increase your wire size then you have to go back to the beginning and recalculate with the larger wire.

This is based on using the same size pipe


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