Square D LAL36400-1021 LAL364001021 - 400A 3 Pole Molded Case Circuit Breaker

The -1021 suffix designates a factory-installed 120/240VAC shunt trip. This allows the breaker to be opened remotely by an external voltage signal, which is essential for automated control or emergency shutdown systems.

This is a unit-mount circuit breaker, meaning it bolts directly to the backplate or mounting pan of industrial enclosures, switchboards, or motor control centers. It does not plug onto a busbar and relies on feed-thru lug connections for both line and load sides.

The standard lugs accept either a single 1 AWG to 600 kcmil conductor or dual 1 AWG to 250 kcmil conductors per phase. They are rated for use with both aluminum and copper wiring.

This breaker utilizes a thermal-magnetic trip unit with an LI (Long-Time, Instantaneous) function. The thermal element provides fixed overload protection, while the magnetic element is adjustable, allowing electricians to fine-tune the instantaneous short-circuit response based on the specific load.

The LAL frame is classified as a legacy molded case circuit breaker by Square D. This specific unit serves as an exact drop-in replacement for existing L-Frame installations, allowing you to restore power without modifying the panel or bus structure.

When upgrading an entire panel, the legacy LAL36400-1021 is typically replaced by the modern PowerPact L-Frame series, such as the LGL36400. If you migrate to the PowerPact platform, you will need to purchase a separate field-installable shunt trip accessory, like the S29386, to replicate the remote trip functionality.

The factory-installed 120/240VAC shunt trip allows the breaker to be integrated with emergency stop (E-stop) buttons, fire alarm control panels, or safety interlocks. When a fault or emergency is detected, the external system sends a voltage signal to the shunt trip, instantly opening the breaker to de-energize the circuit.