Ampacities of aluminum wire

[NMCB13]

I seem to be somewhat confused about table 310.16 specifically with the tempture rating for installing conductors.
I am planing on installing parallel aluminum feeders below grade in 2-1/2" SCH 80 pvc conduit (under 130 ft in length). I am calculating the load to be 400 amp @ 208 volts (3 phase/4 wire). so what tempture rating should I use to obtain the accepted ampacities for the feeders?

NMCB13@netzero.net

 

[bphgravity]

See 110.14(C) of the NEC. It is likely the MAX rating you will be able to utilize is the 75 degree rating, but that depends on the insulation type of the conductors installed and the rating of the terminations at the equipment.

 

[Dennis Alwon]

The temp. rating does not depend on voltage or amperage but rather on the insulation that you are using. I will assume you are using wire rated at 90C. Since the terminals of the breakers and load centers are rated 75C you can use the 75C column. If you are using a insulation that is 60C then you may only use the 60C column.

 

[Dennis Alwon]

I might add that the 90c rating is used for derating purposes.

 

[NMCB13]

Ampacities of aluminum wire

I seem to be somewhat confused about table 310.16 specifically with the tempture rating for installing conductors.
I am planing on installing parallel aluminum feeders below grade in 2-1/2" SCH 80 pvc conduit (under 130 ft in length). I am calculating the load to be 400 amp @ 208 volts (3 phase/4 wire). so what tempture rating should I use to obtain the accepted ampacities for the feeders?

NMCB13@netzero.net

So what it boils down to is what is the tempture rating of the termination method ( lugs on a breaker, lugs on a Discon Sw. etc..).

 

[Dennis Alwon]

So what it boils down to is what is the tempture rating of the termination method ( lugs on a breaker, lugs on a Discon Sw. etc..).

That is correct. Almost all terminals are 75C but if you use 60C wire than you must use the weakest link-- ie 60C column.

 

[NMCB13]

See 110.14(C) of the NEC. It is likely the MAX rating you will be able to utilize is the 75 degree rating, but that depends on the insulation type of the conductors installed and the rating of the terminations at the equipment.

So what it boils down to is what is the tempture rating of the termination method ( lugs on a breaker, lugs on a Discon Sw. etc..).