Conduit fill for mixed schedule 40 & 80 RNC

[shamrock12]

Suppose you have a typical underground feeder run where you would use schedule 40 RNC for the underground portion, but uses schedule 80 RNC where both ends of run goes above ground and is subject to physical damage. Is there an exemption in NEC that would allow you to use the maximum allowable conduit fill of schedule 40 for the entire run (up to a certain length)?

The schedule 80 at both ends of run would act as sleeves to protect the conductors from physical damage like lawn mower, weedeater, etc. Typically those "sleeves" would be about 6 feet each in length (4-1/2 feet above ground and 1-1/2 feet below ground straight down to 90* elbow).

 

[Carultch]

Suppose you have a typical underground feeder run where you would use schedule 40 RNC for the underground portion, but uses schedule 80 RNC where both ends of run goes above ground and is subject to physical damage. Is there an exemption in NEC that would allow you to use the maximum allowable conduit fill of schedule 40 for the entire run (up to a certain length)?

The schedule 80 at both ends of run would act as sleeves to protect the conductors from physical damage like lawn mower, weedeater, etc. Typically those "sleeves" would be about 6 feet each in length (4-1/2 feet above ground and 1-1/2 feet below ground straight down to 90* elbow).

No, there is not an exception.

If you run more than 24" between pull points, it is no longer a nipple, and all possible cross sections need to fit the wire within the required area percentage. In otherwords, base the whole run off of a calculation for SCH80.

Now. It is OK if you use 1.5" SCH40 and appropriate fittings to adapt to 2" SCH80. Probably not recommended though. Because fittings for changing size can be a source of pulling difficulty, when in the middle of a run.