Well now that the mud is stirred up lets clear things up.
Indoor air handler 240v. 15kw elec. heat. Min. circuit ampacity 85 amp. Max OCP 90. Unit has built in 2p 60 and 2p30 amp breakers with single point connection. What size wire to feed unit? (should be simple enough, let’s see)
Someone said-- Per 110-14(c)(1) - all conductors (other than those used for motors) smaller than #1 are to use the 60 degree column for determining ampacity ratings of conductors....that makes your #2 alum worth 75A
(Hmm, guess my #2 Alum SE is too small, but the air handler has a motor in it, um, nah lets not go down that road :> )
Lets look at Article 338 SE Cable, that should help:
Article 338 SE Cable
338.10 (4) (a) interior installations
Type SE cable used for interior wiring shall comply with the installation requirements of Parts I and II of Art. 334, excluding 334.80 (wonder what that says?)
… The ampacity shall be in accordance with the 60C conductor temp. rating….(oh boy, lets see if I got this, 338.10 (4) (a) says to exclude 334.80 which says to use the 60 degree column, therefore I can’t use the 60c column, right?)
Someone else said-- so Table 310-15(b)(6) has no application for him. Being used for the interior would indicate this conductor is a feeder or branch circuit conductor (no 100A circuit breakers here)...unless this is a motor circuit the 60 degree limitations would apply.
(Well, Table 310-15(b)(6) says my #2 alum is rated for 100a if it was a feeder. Just out of curiosity lets look up the definition of “feeder”.)
Definition of Feeder: All circuit conductors between the service equipment,…… and the final overcurrent device.
Hey, my unit has breakers built into it, so this must be a feeder, I should be ok with my #2 alum, right?
Wait. 310-15(b)(6) says: for dwelling units, conductors as listed in Table 310-15(b)(6) shall be permitted as………..feeder conductors that serve as the main power feeder to a dwelling unit……..For
application of this section, the main power feeder shall be the feeder between the main service disconnect and the lighting and appliance branch-circuit panelboard ( I guess my unit doesn’t pass as a lighting and appliance branch-circuit panelboard ,does it?)
AARRRRRRRRRGGGGGGGGGGGHHHHHHHH, I QUIT!!!! I’m going to get a job handing out stickers at Wal-Mart!