[RE-wrenches] Portable power station for surge loads

[Corey Shalanski]

Hi Ray,

RE. the *NEC* Chapter 9 Table 8 resistance adjustment formula: I believe
temperature T2 is the operating temperature of the conductor - not
necessarily ambient temperature... unless I'm mistaken?

Corey Shalanski
Jah Light Solar
Portland, Jamaica


On Sat, Mar 21, 2026 at 7:20 PM Ray Walters <ray at solarray.com> wrote:

> I remember doing some measurements on a long wire run, and being surprised
> that the actual voltage drop was much less than the calculations.  That's
> when I found a small note at the bottom of the NEC Table 8 conductor
> properties used for official VD calculations.   The resistance is listed at
> 167 F (75C), so if you use the adjustment equation in Note 2, it is much
> less VD, and corresponds to reality.  For underground conductors, I might
> use 25C.  Use common sense.
>
> The formula is R2=R1 (1+ a(T2-75))
>
> I made a spread sheet about 15 years ago, that uses that formula for doing
> wire sizing.  Happy to share, if anyone is interested.
>
> Ray Walters
> Remote Solar
>
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