I'm running 3 fans at a distance of 365ft from an MCC.

Fan are:
480, 10HP, 3PH

Given:
14amps from table 430-152
14 * 1.25 = 17.5a for wire size; could run 14THHN, but voltage drop.

Here's my calculation:
total distance I could run = (CM * vd)/(K * I * 1.73)
CM = 10380 from table 8
vd = 480 * .03 =14.4v
K = 12.9 for copper
I= 14a
and 3ph 1.73

Multiply all that out and you get about 465ft.
I'm using #10THHN wire rated at 90C

Here's my derating:
3 fans total for 9 wires = .7
Ambient Temp = .89
#10 THHN wire 90C = 40 x .7 x .89 = 24.92a; more than enough to handle 17.5a at that distance.
I'm running all this in 1" conduit. 3 conductors per motor and a GEC.

So why do I feel uneasy about this, everything checks out I think,,,, I've run the numbers many different ways and still it all adds up to being OK.
What do other people think?, have experienced?