Derating beyond a disconnect switch

[ckdckd]

Hi All,

I could not find this previously discussed, so please forgive me if it is a repeat.

I am on the 2011 NEC.

I am looking at a 480V circuit from the basement of bldg going to an equipment shelter located on the roof. Conduits will run vertical through the building to a roof penetration and then across the roof for about 50' until it enters the shelter. Once in the shelter it hits a disconnect switch, then goes into a transformer to give me 208Y/120V.

I am doing ampacity adjustment because the conductors run across the roof. My question is whether or not the code requires the adjustment to continue past the disconnect to the primary lugs on the transformer, OR if I can size the conductors between the disconnect and transformer without adjustment. The length of these conductors may exceed 10', the exception in 310.15(A)(2) doesn't apply.

I would be happy with a code section to answer whether or not the disconnect would be a point whereby I reevaluate for the load side conductors?

 

[packersparky]

If the raceways and transformer are under the shelter, they might not be exposed to sunlight. If they are not exposed to sunlight, the adjustment factors would not need to be applied. Providing shade for the raceways can often be cheaper than increasing wire size.

 

[GoldDigger]

But you would still need to allow for the ambient temperature above the roof without the additional solar adder.

 

[ckdckd]

If the raceways and transformer are under the shelter, they might not be exposed to sunlight. If they are not exposed to sunlight, the adjustment factors would not need to be applied. Providing shade for the raceways can often be cheaper than increasing wire size.

The conduits are exposed to sunlight for about 50'.

The exception in 310.15(A)(2) refers to adjacent portions of a circuit. So, I guess my question is whether the conductors on the load side of the non-fused disconnect are considered to be an adjacent portion of the circuit conductors that are on the line side of the switch.