Square D LLA36400U31X - 400 A, 600 V, 3-Pole Plug-In Circuit Breaker | AmpState

Meet the Square D LLA36400U31X—a 400 A, 600 V, 3-pole plug-in molded case circuit breaker designed to shield panelboards and load centers from overcurrent and short circuits. Available from AmpState, this unit blends industrial-grade protection with fast, hassle-free serviceability.

Fast plug-in connection for quick installation and effortless replacement, minimizing panel downtime during upgrades or routine maintenance.

Thermal-magnetic trip unit delivers stable, repeatable protection by reacting to both sustained overloads and sudden short-circuit events, helping prevent wiring damage and equipment failure.

Engineered to be compatible with matching OEM load centers and panelboards, this 3-pole breaker provides a dependable, coordinated protection scheme for multi-phase electrical distribution. It’s suitable for residential, commercial, and light industrial applications where robust protection and easy maintenance matter.

Key specifications

• Manufacturer: Square D
• Part Number: LLA36400U31X
• Type: Thermal-magnetic molded case circuit breaker
• Amperage rating: 400 A
• Voltage rating: 600 V
• Number of poles: 3
• Mounting style: Plug-in
• Application: Branch circuit overcurrent and short-circuit protection

Ideal use cases

Use the LLA36400U31X as the main feeder protection in commercial panels or as a high-capacity protective device in light industrial setups. It’s well-suited for panel replacements and upgrades where fast, reliable plug-in installation minimizes downtime while maintaining a coordinated protection scheme across multi-pole circuits.

Why choose this unit

This breaker doesn’t just meet the basics—it delivers a proven protection strategy tuned for reliability in demanding environments. The combination of a plug-in form factor, a robust thermal-magnetic trip system, and OEM-compatible compatibility means you get quick serviceability without compromising safety or coordination with your existing load centers.

What to know before installation

Ensure compatibility with your OEM load centers and panelboards to maintain coordinated protection. The plug-in design is optimized for rapid replacement and streamlined field service, reducing downtime during maintenance or panel upgrades.