Conduit Fill Question

[RRelec]

what are some of your guys rule of thumb about deciding to go to a bigger size, even though your within the code?

Is it more like with a number of 90's and a longer run I would want to keep my fill to more like 30%.

Bigger isn't always better. Ever wonder why 2 conductors are limited to 31%? Read the FPN's under Table 1 Chapter 9. I do however consider the length of a run foremost, along with routing, prior to installation, and then who I have to pull it with.

Just my Thoughts

R

 

[RRelec]

This is 90 degree C conductor, THHN, in a conduit. The 60 degree C column would come into play at the terminations if they were rated for 60 degrees C.

I would agree with you if the OP was discussing larger wire sizes falling under 110.14(C)(1)(b), or connecting a motor as in 110.14(C)(1)(a)(4). But the OP has 14's, 12's and #8's. I was just trying to clarify the intent of 110.14(C)(1), so someone reading this post without prior knowledge of these codes didn't start using the 90C column for 60C terminations. Also see 310.15(B) FPN. Maybe I should have explained it better as to my reply. I did think it was clear.

"As in the OP, I would assume 110.14(C)(1)(a)(2) applies."

See Below,
Quote:
"My final answer for ampacity cannot be higher than the value in the 75C column, but I don't have to start there."

I just assumed Charlie B was refering to the OP since this thread is based on that. I didn't read into his reply as refering to larger wire/breaker sizes. If you feel that I am still wrong, please help me understand. I always try to share information and certainly don't ever mean to affend anyone else trying to do the same. I apoligize if I have done so.

I have always said "no matter how smart you may think you are, there is always somebody smarter".

R

 

[infinity]

I would agree with you if the OP was discussing larger wire sizes falling under 110.14(C)(1)(b), or connecting a motor as in 110.14(C)(1)(a)(4). But the OP has 14's, 12's and #8's. I was just trying to clarify the intent of 110.14(C)(1), so someone reading this post without prior knowledge of these codes didn't start using the 90C column for 60C terminations. Also see 310.15(B) FPN. Maybe I should have explained it better as to my reply. I did think it was clear.

"As in the OP, I would assume 110.14(C)(1)(a)(2) applies."

I wouldn't assume that 110.14(C)(1)(a)(2) applies. Almost all terminations are now rated for 75 degrees C so if I were making an assumption it wouldn't be that THHN in conduit would require the 60 degree C ampacity rating. This would fall under 110.14(C)(1)(a)(3).