__Example__: 15kV 1/0 AWG shielded single conductor copper cable, no neutral (select smallest neutral size in table)

__Using table in IEEE Std. 835-1994 (pp. 349)__:

__Using formula from IEEE Std. 835-1994, Section 3.4.1 (pp. Intro-10):__Adjusting for ambient temperature, the multiplier obtained is 1.03.

__Using formula from IEEE Std. 835-1994, Section 3.4.2 (pp. Intro-10)__: Adjusting for maximum conductor temperature, the multiplier obtained is 1.08.

__Derating for depth__

__Ampacity rating for 1/0 cable with 1/6 neutral__: 139A

I = 139*1.03*1.08*.91 = 140A (rounding down)

:

__Derating for depth__: 1-(20*12-30)/12*.06 = -.05

I = 139*1.03*1.08*-.05 = -7A (rounding down)

How can this be possible? Also, is there no reason to account for the difference in ampacity between conductors at the top of a duct bank and conductors at the bottom of the same duct bank?

## Comment