Sizing wire gauge using VDI

[albertcuy]

Hi All,

i've been doing some calculations using the VDI method, but the recommended AWG size i'm getting seems off.

Anyways, here are the parameters for the panel i plan to use:

160 watts solar panel
Vmp = 18V
Imp = 8.89A
cable length(panel to charge controller): 32.8 feet
VD% = 2

So putting it all in the formula:

VDI = (8.89 x 32.8 ) / ( 2 x 18 ) = 8.0998

...which gives us a recommended AWG of 8 (VDI rounded down to 8 ) or 6( VDI rounded up to 12)


What i don't understand is, why should i use AWG 6/8, which has max amps upwards of 55 amps, when my panel maxes out at 8.89A?


tia

 

[MisterSandals]

Interactive Wire Size Calculator

Battery Chargers, Inverters, Solar Components, and Wiring Supplies for Boats, RVs, and Off-Grid Applications.

baymarinesupply.com

 

[Zil]

Because you be looking at voltage drop, not ampacity.