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Discussion Starter · #1 ·
I have an app on my phone that says you can have 25 conductors in a 1" EMT to occupy 38%. The max allowed according to the app is 40%. Is that right? Where would I find this in the NEC? Is there a derating factor that this app is already doing? 25 just seems like an awful lot in a 1"
 

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Discussion Starter · #3 ·
Thanks! So it looks like 26 #12 THHN-2 wires is what the NEC allows. Is that current carrying conductors? Is there a derating factor or can you put 26 current carrying conductors in the EMT and rock and roll?
 

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travis13 said:
Thanks! So it looks like 26 #12 THHN-2 wires is what the NEC allows. Is that current carrying conductors? Is there a derating factor or can you put 26 current carrying conductors in the EMT and rock and roll?
You cannot put that many cccs in a conduit. Once you put 9 cccs in a conduit you derate by 50%, even if it's 9 number 12s in a 4" EMT.

So technically you could do that but your new ampacity will be unusable, unless it's control circuitry
 

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You don't derate at 50% until you're at 10 ccc. My rule of thumb regarding 120v ckt's with their own neutrals is; 7- 120v ckts using #10awg in a 1" conduit till I get to a point where I can split the circuitry and drop down to #12.
 

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I rewrote all the annex C tables for the 2014 NEC as there were errors in the old tables. I also expanded it to the point of ridiculousness--- For instance, you can put 4395 KF-1 conductors 18awg in a 6" PVC conduit...

Good luck with that pull....:laughing:
 

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travis13 said:
So does this mean 13 THHN #12 in 1" emt is the max ccc if annex c states 26?
As stated earlier. There is a table regarding derating. Neutrals and hots both count as CCC's. The only time you don't derate those wires is if there in a nipple less than 24" long You could put 26 ccc In that pipe but you'd have to derate the conductors by 45%.
 

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So does this mean 13 THHN #12 in 1" emt is the max ccc if annex c states 26?
The percentage does not mean 50% of the number of conductors. If for instance you had 20 conductors of #12 THHN then we must derate the ampacity of the conductor 50%. So at 90C #12 thhn is rated 30 amps. 50% of 30 is 15 amps so you could no longer install a 20 amp overcurrent protective device but rather would have to install a 15 amp overcurrent protective device.
 

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Because in a multiwire branch circuit as stated the neutral carries the unbalanced load and in effect does not add to the amount of current in the conduit.




Here is something written by Trevor at Mike HolMike HolMike Holt
Here's some examples of when to count the neutral as a CCC:

208Y/120 volt system-different circuit types:

A)- 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
B)- 3 wire circuit w/ 2 ungrounded, 1 neutral = 3 CCC's
C)- 4 wire circuit w/ 3 ungrounded, 1 neutral = 3 CCC's*

Notes:
A)- A normal 2 wire circuit has equal current flowing in each of the circuit conductors so they both count as CCC's.
B)- In this circuit the neutral current will be nearly equal to the current in the ungrounded conductors so the neutral counts as a CCC
C)- In this circuit the neutral will only carry the imbalance of the current between the three ungrounded conductors so it is not counted as a CCC, with one exception, *if the current is more than 50% nonlinear then the neutral would count as a CCC.

120/240 volt system-different circuit types:

D)- 2 wire circuit w/ 1 ungrounded, 1 neutral = 2 CCC's
E)- 3 wire circuit w/ 2 ungrounded, 1 neutral = 2 CCC's

Notes:
D)- A normal 2 wire circuit has equal current flowing in each of the circuit conductors so they both count as CCC's.
E)- In this circuit the neutral will only carry the imbalance between the two ungrounded condcutors so the neutral is not counted as a CCC.
 

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Discussion Starter · #16 ·
Ok guys I've looked at the tables mentioned, and sorry for all the questions. I'm a second year apprentice and we haven't been pounding code.

Ok so let's say I have 26 ccc in a 1" (which you can't do) but going by that table it falls in the 45% range. So this means that all #12 wires are now rated at 13.5A?
 

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Ok guys I've looked at the tables mentioned, and sorry for all the questions. I'm a second year apprentice and we haven't been pounding code.

Ok so let's say I have 26 ccc in a 1" (which you can't do) but going by that table it falls in the 45% range. So this means that all #12 wires are now rated at 13.5A?
That is correct assuming 90C wire is being used and no other derating factors are needed.
 
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