Terminal and wire temperature for sizing conductors

[sjohns]

I have a question; the installation is using #12 AWG type THWN-2 copper conductors and the terminations are rated 60 degrees C. There are six current carrying conductors, in 3/4" conduit, running through an attic with an ambient temperature of 132 degrees F. The load on the conductors is 16A non-continuous.

My calculations are as follows:
[FONT=Swis721 BT, sans-serif]Conductor sizing calculations[/FONT]
[FONT=Swis721 BT, sans-serif]12 AWG THWN-2 (90 degree C) = 30A[/FONT]
[FONT=Swis721 BT, sans-serif]For six current carrying conductors derate 80%[/FONT]
[FONT=Swis721 BT, sans-serif]30A x 0.8 = 24A[/FONT]
[FONT=Swis721 BT, sans-serif]for ambient temperature of 132oF derate 71%[/FONT]
[FONT=Swis721 BT, sans-serif]24A x 0.71 = 17A[/FONT]
[FONT=Swis721 BT, sans-serif]The load is 16A, 12 AWG at 60oC is rated 20A the OCPD is rated 20A[/FONT]
[FONT=Swis721 BT, sans-serif]The conductors are appropriate for the application. Correct?[/FONT]

 

[iwire]

Does the circuit feed recptacles.

 

[Carultch]

I have a question; the installation is using #12 AWG type THWN-2 copper conductors and the terminations are rated 60 degrees C. There are six current carrying conductors, in 3/4" conduit, running through an attic with an ambient temperature of 132 degrees F. The load on the conductors is 16A non-continuous.

My calculations are as follows:
Conductor sizing calculations
12 AWG THWN-2 (90 degree C) = 30A
For six current carrying conductors derate 80%
30A x 0.8 = 24A
for ambient temperature of 132oF derate 71%
24A x 0.71 = 17A
The load is 16A, 12 AWG at 60oC is rated 20A the OCPD is rated 20A
The conductors are appropriate for the application. Correct?

Read 240.4(B), and determine if your circuit qualifies for the next-size-up rule. If it does qualify, than #12 Cu wire would be sufficient. If it does not, then you need to have as much wire amps as OCPD after conditions of use and as terminal ampacity before conditions of use.