AC unit and motor cale sizing

[mbrooke]

If an AC or had an FLA of 18 amps under the 2005 NEC, according to table 310.16 I could use #14 NM-B or THHN in conduit? However, with 310.16 changing to 310.15 (B) (16) I am now required to use #12 if the wire is NM-B or terminals are rated 60 degrees, while I could still use #14 THHN in conduit with 75*C terminals?

Same with a motor under 2014?

 

[mbrooke]

*meant cable in title, my bad.

 

[augie47]

For clarity, if I may substitute MCA for your FLA, I am in agreement with your post.

 

[Smart $]

If MCA, you got it.

If FLA, it gets multiplied by 125% for sizing conductors.

 

[mbrooke]

For clarity, if I may substitute MCA for your FLA, I am in agreement with your post.

So simply changing the 60*C ampacities in 310.16 requires increasing the size?



Anyone know why 310.16 was changed or know the ROP?

 

[don_resqcapt19]

...
Anyone know why 310.16 was changed or know the ROP?

Proposal 6-99 for the 2011 code. Part of the substantiation is below:

Acceptance of this proposal will harmonize the ampacity values between NEC Table 310.16 and CEC Tables 2 and 4 with technically substantiated values. ...

 

[mbrooke]

Proposal 6-99 for the 2011 code. Part of the substantiation is below:

Ok. Anyone have the IEEE (IEEE Std 835-1994)

equations? Seems silly but I guess they have something to back it up.