A sleeve is a short piece of tubing used for mechanical protection, often where a cable passes through a floor. A sleeve may be made of conduit.
The conduit table may be used for round sleeves. If the sleeve is square or rectangular it may be good to use the tables for a circle included in the shape.
Use good judgement.
Bill
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"Why not the best?"
Jimmy Carter
Yes, I believe that conduit table in the NEC can be used since a short sleeve virtually does not change the heat transfer characteristics that drive the cable ampacity.
Since the sleeve length could be less than 600 mm, NEC 2014 Art. 310.15 Ampacities for Conductors Rated 0–2000 Volts.(B) Tables.(3) Adjustment Factors.(a):
2) Adjustment factors shall not apply to conductors in raceways having a length not exceeding 600 mm (24 in.). That means-in my opinion-if a sleeve filled with cables from a cable tray passes through a wall of not more than 24" and continue in other cable tray no other adjustment it will need.
