Square D LDA36400U43X - 400 A, 3-Pole Plug-In Circuit Breaker | AmpState

The Square D LDA36400U43X is a 400 A, 3-pole plug-in molded case circuit breaker designed to protect your panelboards and loadcenters from overcurrent and short-circuit events. Engineered for dependable performance in residential, commercial, and light industrial environments, this breaker delivers quick installation and robust, consistent protection when it matters most.

Why this breaker stands out

• Fast plug-in connection for streamlined installation and effortless replacements, minimizing downtime during upgrades or service calls.
• Thermal-magnetic trip unit provides stable, repeatable protection by combining thermal overload sensing with magnetic short-circuit tripping—balancing sensitivity and reliability.
• OEM panelboard compatibility engineered to fit and function with matching Square D loadcenters and panelboards, ensuring seamless integration and labeling consistency.
• High-current, three-phase protection suited for large residential feeders, commercial equipment, and light industrial circuits requiring 400 A capacity.
• Plug-in molded case design offers durable enclosure protection and easy field service, ideal for panelboard upgrades and maintenance.

Technical snapshot

• Manufacturer: Square D
• Part Number: LDA36400U43X
• Type: Thermal-magnetic molded case circuit breaker
• Amperage Rating: 400 A
• Number of Poles: 3
• Mounting Style: Plug-in
• Application: Branch circuit overcurrent and short-circuit protection in panelboards and loadcenters

Ideal applications and use cases

Use this 3-pole, 400 A plug-in breaker to safeguard three-phase equipment and large feeders in residential complexes, commercial offices, retail centers, or light industrial facilities. It’s well-suited for main distribution panels where high-current protection is required, as well as subpanels feeding motor loads, HVAC equipment, or heavy electrical circuits. When you need reliable protection with quick replacement in OEM-aligned panels, this Square D breaker is a precise fit.

Installation and maintenance tips

To get the most from the LDA36400U43X, ensure you’re installing it in a panelboard or loadcenter that accepts Square D plug-in molded case breakers and that the panel’s rating supports a 400 A, 3-pole device. Rely on the fast plug-in connection to minimize outage time during upgrades or service work, and rely on the thermal-magnetic trip to maintain consistent protection against both overloads and short circuits. Regularly inspect panel labeling to confirm compatibility and ensure proper alignment with the bus stabs for reliable operation.

Why AmpState supports this choice

As a trusted source for genuine Square D components, AmpState provides access to authentic LDA36400U43X breakers along with trusted support for selecting the right protection devices for your panelboard or loadcenter. With compatibility, performance, and installation efficiency in mind, this 400 A, 3-pole plug-in breaker is a practical, reliable solution for demanding electrical protection needs.