Max number of conductors

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jsab73

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NJ
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Electrician
What is the maximum number of #10 THHN wires can I fit in a 2” emt conduit run using the adjustment factor?
 
We would need to know the final ampacity of the conductor that you're looking for. For example after adjustment do you only need 15 amp conductors?

Welcome to the Forum. :)
 
So the maximum number of CCC's (current carrying conductors) would be 20 if using 90° C conductors and if the next size up rules in 240.4(B) do not apply.

T310.16: #10 THHN = 40 amps
T310.15(B)(3)(a): 10-20 CCC's = 50% ampacity adjustment factor
40amps *50% = 20 amps
 
Just note infinity's reply is for the number of current carrying conductors. Depending on various factors, some conductors may not be current carrying for purposes of derating (generally neutral conductors for multi wire Branch circuits).
 
electrofelon said:
Just note infinity's reply is for the number of current carrying conductors. Depending on various factors, some conductors may not be current carrying for purposes of derating (generally neutral conductors for multi wire Branch circuits).
Click to expand...
That's correct. It would be a maximum of 20 CCC's to maintain the 20 amp rating of the conductors. MWBC neutrals and EGC's are not counted in that calculation.
 
jsab73 said:
What is the maximum number of #10 THHN wires can I fit in a 2” emt conduit run using the adjustment factor?
Click to expand...
2023 Texas
You have 2 adjustment factors to consider.
One is the number of current carrying conductors in a raceway.
The other is the ambient temperature.

These requirements are found in the caption of T. 310.16 and foot notes, too.
Here's the maximum number for any conductor(s) any size.

Caption says ..."no more than 3 current carrying conductors in........."
Note number 1 says... " if installed in other than 30 degrees Celcius or 86 degrees Farenheit......"

So, 3 conductors if you install them in an ambient temperature as indicated above.
And, "......no more than 3 current carrying conductors in a raceway,..........."

Not very many according to the rules.

So it takes two more tables to fit the puzzle together.

T. 310.15(B)(1)(1) for ambient temperature correction.
T.310.15 (C) (1) Adjustment Factors for more than 3 current carrying conductors.

Thanks for reading
Comments accepted
TX+MASTER#4544
 
So no matter what conduit trade size you use ,you can only fit 20 CCC #10 thhn in the conduit…4”-1 1/4?
 
jsab73 said:
So no matter what conduit trade size you use ,you can only fit 20 CCC #10 thhn in the conduit…4”-1 1/4?
Click to expand...
Yes with an exception (nipple).

What's important is the CCC, 20 amp OCPD and #10 THHN.

The #10 THHN 90c conductor is easy.
The 20 amp OCPD is easy.
The CCC no to much. What is considered CCC will and can change the quantity of #10's which then the raceway is selected.

Let's say the branch circuits are line to neutral with each line having it's own neutral ( grounded conductor).
That would be 10 circuits, 20 wires and an EGC if selected or required. Race way fill at 40% would be selected for 21 #10 THHN conductors.

Now there is a catch to consider. Let's say this is a raceway 24" or less ( nipple). Now no derate is required and you use a 60% fill.
Raceway size @60% and see how many #10's will fit current carrying or not.

Another example would be line to line 3 phase 4 wire circuits or MWBC. The netural may not count if so you now have 18 line conductors, 6 neutrals and an EGC if selected or required. That would be 25 #10 @ 40% fill, then select raceway.
Since we're allowed 20 you could add two more CCC which would make it a total of 27 #10's or 19 single pole circuits.

Another item to consider with what is current carrying in way of the neutral. This would be single phase from a three phase 208/120 Y system. In this case the neutral counts if it's a single phase panel that they originate in or two line and a neutral from a three phase panel. This would be 12 line, 6 netural and 1 EGC if selected or required. Again since we're allowed 20 you could add one more line to neutral circuit. This would give you 21 #10's or 13 single pole circuits.

Then we have a 3 phase 4 wire delta high leg system. In this case the neutral is treated like single phase 120/240. If MWBC you would have 20 line conductors(CCC),10 neutrals and an EGC if selected or required. That would be 31 #10's @ 40% fill then select raceway. This would give you 20 single pole circuits.


For the purpose of CCC you need to conder which are and which are not considered CCC based on the NEC.

I have left out linier and non linear for simplicity.
 
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