Type UF Ampacity

[c_picard]

340.80 Ampacity. The ampacity of Type UF cable shall be
that of 60?C (140?F) conductors in accordance with 310.15.

340.112 Insulation. The conductors of Type UF shall be
one of the moisture-resistant types listed in Table
310.104(A) that is suitable for branch-circuit wiring or one
that is identified for such use. Where installed as a substitute
wiring method for NM cable, the conductor insulation
shall be rated 90?C (194?F).

Question: When selecting conductor size for a branch circuit, using UF as a substitute for NM, the UF must be constructed using 90deg conductors, and I use the ampacity listed in the 60deg column. Correct?

 

[roger]

Correct.

Roger

 

[c_picard]

Roger, Roger.

What's our Vector? Victor?

 

[Dennis Alwon]

I agree with Roger but will add that if derating is involved you may use the 90C rating as long as the final ampacity used is not larger than the 60C rating

 

[c_picard]

Right, the same way one would be able to use the 90C column so long as the resulting ampacity did not exceed the 75C column for terminal ratings.

 

[Dennis Alwon]

Right, the same way one would be able to use the 90C column so long as the resulting ampacity did not exceed the 75C column for terminal ratings.

Right only in this case the weakest link is the UF so 60C is required not 75C :thumbsup:

 

[suemarkp]

I've never seen in explicitly in the code, but modern UF is typically labeled UF-B (just like NM and NM-B). I'm assuming this means it is 90C rated (for derating purposes only), but the book doesn't say that like it does for NM.

 

[infinity]

Is there another UF cable manufactured besides UF-B?

 

[jumper]

IIRC neither NM-B and UF-B is a recognized NEC designation, the "-B" just means that it means it was manufactured under modern code as having 90C conductors-else you have the old style 60C stuff.

A UL thing I guess.

 

[kwired]

IIRC neither NM-B and UF-B is a recognized NEC designation, the "-B" just means that it means it was manufactured under modern code as having 90C conductors-else you have the old style 60C stuff.

A UL thing I guess.

NEC does mention NM-B in the informational note after 334.112, and basically says any cable marked NM-B meets the 90C requirement for conductor insulation mentioned in 334.112.