Calculating the ampacity of copper and aluminum busbars has never been easier.

Busbars are used in switchboards, load centers, and panelboards. Busbars are generally uninsulated. The constant amperage for a bare copper wire (Cu) busbar must not exceed 1000 A sq in. of the cross-sectional area of its bar. 

Aluminum (Al) busbars may not endure constant amperage exceeding 700 A sq in. of the cross-sectional area of the bar per 366.23 (A). To calculate the ampacity of a busbar, apply the following equation.

Busbar ampacity= T x W x constant, where busbar ampacity = ampacity of busbar (in A)

f = thickness (in in.)

w = width (in in.)

constant 1000 for Cu and 700 for Al

Examples:

What is the ampacity of a ¼” thick by 3″ wide Cu busbar?

Busbar ampacity= T x W x Constant

Busbar ampacity 0.25” x 3” x 1000

Busbar ampacity=0.75 x 1000

Busbar ampacity 750 A

What is the ampacity of a ½” thick by 2” wide Al busbar?

Busbar ampacity=T x W x Constant

Busbar ampacity 0.50” x 2” × 700

Busbar ampacity= 1x 700

Busbar ampacity= 700 A