Ampacity of UF cables in a pipe sleeve.

[james blake]

Hey Guys. I just need some verification here. We found three 12/2 copper UF cables that leave a panel thru a pipe sleeve that is over twenty four inches long, and enters the ground. Taking derating into consideration, shouldn't the conductors be derated from 20 amps to 16 amps?

 

[suemarkp]

Are they UF or UF-B? I think UF-B is a 75C or 90C conductor for derating purposes, but still limited to 60C max for ampacity only.

It is also strange that the NEC has changed the 60C ampacity for #14 and #12 wire in 2011. It was 25A for #12 even at 60C in years past. That can cause some issues in upgrades....

 

[jumper]

Hey Guys. I just need some verification here. We found three 12/2 copper UF cables that leave a panel thru a pipe sleeve that is over twenty four inches long, and enters the ground. Taking derating into consideration, shouldn't the conductors be derated from 20 amps to 16 amps?

Yes. 24 inches applies to nipples not sleeves for UF. Install does not meet the exception.

Exception No. 4: Derating factors shall not apply to underground
conductors entering or leaving an outdoor
trench if those conductors have physical protection in the
form of rigid metal conduit, intermediate metal conduit, or
rigid nonmetallic conduit having a length not exceeding
3.05 m (10 ft) and if the number of conductors does not
exceed four

 

[james blake]

Are they UF or UF-B? I think UF-B is a 75C or 90C conductor for derating purposes, but still limited to 60C max for ampacity only.

It is also strange that the NEC has changed the 60C ampacity for #14 and #12 wire in 2011. It was 25A for #12 even at 60C in years past. That can cause some issues in upgrades....

The cable is UF B