Table B.310.15(B)(2)(11) ** In 2014 Code Book

[Ravenvalor]

Hello,

Does anyone know if one can install 16 - current carrying #12 conductors through about 20' - of 3/4" EMT and keep them on a 20-amp circuit breaker if each conductor is pulling 9-amps?

According to my interpretation of Table B.310.15(B)(2)(11) ** In the 2014 Code Book if I use only 9 - conductors then it is legal. What is it about the 2 - ** in the Table on the third row that would prevent me from using a 20-amp breaker under the conditions described above? The percent values are both 70%.

Thank you,

 

[Carultch]

Hello,

Does anyone know if one can install 16 - current carrying #12 conductors through about 20' - of 3/4" EMT and keep them on a 20-amp circuit breaker if each conductor is pulling 9-amps?

According to my interpretation of Table B.310.15(B)(2)(11) ** In the 2014 Code Book if I use only 9 - conductors then it is legal. What is it about the 2 - ** in the Table on the third row that would prevent me from using a 20-amp breaker under the conditions described above? The percent values are both 70%.

Thank you,

The wire ampacity needs to at least "round up" to the amp rating of the breaker, per 240.4(B).

Assuming 30C ambient, your 16 qty #12 Cu wires have an ampacity of 15A, which is an exact match to a standard OCPD. You need to exceed the previous OCPD, in order to use the next larger size. If your ambient temperature naturally is less than 30C, you could do this, but that is a rare scenario. In otherwords, don't count on air conditioning to make it colder than 30C.

 

[luckylerado]

Hello,

Does anyone know if one can install 16 - current carrying #12 conductors through about 20' - of 3/4" EMT and keep them on a 20-amp circuit breaker if each conductor is pulling 9-amps?

According to my interpretation of Table B.310.15(B)(2)(11) ** In the 2014 Code Book if I use only 9 - conductors then it is legal. What is it about the 2 - ** in the Table on the third row that would prevent me from using a 20-amp breaker under the conditions described above? The percent values are both 70%.

Thank you,

Are you asking about 16 conductors or 9?

** points to 240.4D and does not prevent a 20A breaker. 310.15(b)(3) will dictate what the max ampacity is and therefore the max OCP is in this case.

 

[Dennis Alwon]

16 conductors- 50%--- 30 amps x 50% means 15 amp breaker max

 

[Ravenvalor]

Are you asking about 16 conductors or 9?

** points to 240.4D and does not prevent a 20A breaker. 310.15(b)(3) will dictate what the max ampacity is and therefore the max OCP is in this case.

I am asking about 16 conductors. I see that I was referring to the wrong table.

Thanks,

 

[Ravenvalor]

Thanks for all of the great help.