ECN Forum Forums General Topics of the Trade General Discussion Area #2 Alum.

Whats the ampacity Of #2 Alum SE cable? Interior use. No derating factors.


Glenn

Without revealing a lot more, apply 110-14(c)(1), use the 60 deg table, it is 75 amps.

Se cable conatins RHW or XHHW conductors and should be marked as such. RHW2 or XHHW2 markings indicate 90 degree conductors and allow ampacity of 100 amps (310.16) RHW and XHHW should use 75 degree column and that allows 90 amps. For service entrance cables and main feeders to a dwelling unit, throw all that away and figure 100 amps for #2 AL se cable. table 310.15(B)(6)

The 90 degree column is NOT to be used to determine the ampacity or 'rating' of a conductor...this column is used ONLY for derating factors. Only the 60 & 75 degree columns are used for determining the 'rating' of a conductor.

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 as George said.

It will depend on the temperature rting of the termination as the other posts are pointing out.

Every 100 amp breaker I've looked at for a long time is rated for 75 degree conductors, so 110-14(c)(1)(c) would allow the 100 amp rating permitted by table 310-15(b)(6) for residential applications. Otherwise, the cable is good for 90amps, provided the connections are identified for use at 75 degrees.

Tom

I can kick up some mud.

If the service entrance is 100amp with #2 al, then you have 100amp #2 wire indoors.

lacking that it looks like 75amps.

Tom -the original post from Glenn indicated this #2 alum was being used for the interior (nothing said about SE conductors)....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 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?)

334.80 Ampacity.
… 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!

Glenn

I think it's a feeder, but not a feeder as described in 310.15(B)(6).
I think you'll find the terminals will be rated for 75C. ...and if you do...
I think that, according to 110.14(C)(1)(a)(3), you should be able to use the 75 deg. column and the 90 amp rating.

THanks Redsy (I think)
Anybody with a more definitive answer?

By the way Wal-Mart didn't work out so I'd like to practice on you with my new job.

Would you like fries with your order?

Glenn