Solar Wire Sizer NEC 690.8

ZkDev

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About this app

Wire Sizing for Solar PV per NEC 690.8 Ampacity

# What it does
Calculates required AWG / kcmil wire size for PV DC and AC conductor runs per NEC 690.8: maximum circuit current 125% of Isc, then BOTH printed checks of 690.8(B) — base ampacity vs 156% and temperature/bundling-corrected ampacity vs 125%.

# Features
- Module Isc input
- Max circuit current = Isc x 1.25 (NEC 690.8(A)(1))
- Two-step ampacity check per NEC 690.8(B)(1) and (B)(2)
- Copper and aluminum conductors, 14 AWG to 500 kcmil
- Conductor temperature rating (60/75/90°C)
- Multiple conductor adjustment (NEC 310.15(C)(1))
- Ambient temperature correction (NEC 310.15(B)(1))
- Adjusted ampacity vs required current
- AWG / kcmil result with safety margin

# Made for
Solar installers, electrical contractors, PV technicians, code inspectors, apprentice electricians.

# Optional Pro Upgrade — $2.99 one-time
The following features require a separate one-time in-app purchase. They are not required to use the calculator:
- Calculation history (saved & searchable)
- PDF report export with NEC references
- Dark theme
- Ad-free experience

What’s new

Conductor sizing now follows the printed two-step NEC 690.8(B) check:
- (B)(1) base ampacity vs 156% of Isc, (B)(2) corrected ampacity vs 125% - no more over-derating on hot or bundled runs
- Voltage drop now computed at 125% max circuit current (was 156%)
- Aluminum 300 kcmil corrected to printed 310.16 values (195/260 A)