Recommended standard bar
1/4 × 2 in
500 A screening ampacity
UL 508A §32 · manufacturer confirmation required
Calculator 20 / UL 508A §32
Busbar sizing
Conservative preliminary busbar sizing with typical catalog dimensions and voltage drop.
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VoltForgeBusbar Sizing Report
Project / job name: —
Date: —
Site: voltforgelab.com
Inputs
| Load / material | 400 A / copper |
| Ambient / rise / length | 40 °C / 65 °C / 12 in |
Results
Engineering disclaimer: This design aid is not a substitute for engineering judgment. Confirm final design with a licensed professional engineer and the authority having jurisdiction.
Minimum area
0.400 in²
Rule-of-thumb area requirement
Engineering screening rule; not NEC ampacity
Recommended bar
1/4 × 2 in
500 A; 25% margin
UL 508A §32 · typical catalog size
Voltage drop
0.248 V
Across 12 in, two-way copper/aluminum resistance model
NEC 215.2(A)(1) voltage-drop guidance
How this was calculated
Required cross-section = 400 A ÷ 1000 A/in² = 0.400 in². The next larger typical catalog size is 1/4 × 2 in. Ambient and rise are recorded design inputs; manufacturer thermal tables govern.
Rule-of-thumb only: Confirm ampacity, spacing, bracing, joints, enclosure temperature, and short-circuit withstand with the busbar manufacturer. UL 508A §32 and applicable UL 891 construction requirements govern.