Why do not use the Lowest temperature rating column?

[Alex_rg15]

(90-degree rated wire installed on 75-degree terminations can use the 90-degree column ampacity for the correction factor calculation)

how many amps can run through seven-#1 rhh conductors when installed in rmc to an outdoor panel with 75-degree celsius temperature ratings where the ambient temperature is 88 degrees fahrenheit?

I know the answer is 97.44 Amps

I got this by
Step 1
#1 RHH is 145 amps table 310.16 (b)
Step 2
Adjustment factor for more than three current-carrying conductors
7-9 70% table 310.15(B)(3)(a)
Step 3
Ambient factor
table 310.15(b)(1)(1)
Column 90 C
0.96
Step 4 math
145 amps X 70% X 0.96
97.44 amps
My question is why I need select the 0.96 from Column 90 C, and not 0.94 from Column 75 C from table table 310.15(b)(1)(1)
When the the panel is installed at 75 C temperature ?

 

[wwhitney]

The way I think about it is that the NEC places two separate types of minimums on conductor size.

The first is based on the conductors in the run of the cable/conduit and the conditions there (and if those conditions vary, it becomes multiple separate conditions). That considers conductor insulation rating, ambient temperature, and number of CCCs. It also looks at the load without any continuous use factors. It doesn't consider anything about the terminations like their temperature rating.

The second is based on the terminations at the ends of the conductor. That is based on the termination temperature rating but ignores the ambient temperature and number of CCCs. It also includes a 125% factor on any continuous loads.

Cheers, Wayne