Square D MJA36400 - 400 A, 600 V, 3-Pole Plug-In Circuit Breaker | AmpState

The Square D MJA36400 is a rugged, plug-in molded case circuit breaker designed to deliver fast, reliable overcurrent protection for three-phase systems. With a 400 A rating and 600 V maximum, this 3-pole device is a robust choice for panelboards and load centers that demand dependable branch circuit protection in residential, commercial, and light industrial settings.

• Fast plug-in connection enables quick installation and stress-free replacement, minimizing downtime during maintenance or panel upgrades.
• Thermal-magnetic trip unit provides stable, repeatable protection against overcurrent and short circuits across varying temperatures, helping prevent nuisance trips and equipment damage.
• OEM-compatible design is engineered to fit matching Square D panelboards and load centers, ensuring a clean, reliable integration without compatibility concerns.
• Versatile 3-pole configuration supports three-phase distribution, ideal for larger branch circuits and feeders in commercial and light industrial environments.

Technical specifications

• Manufacturer: Square D
• Part number: MJA36400
• Type: Thermal-magnetic molded case circuit breaker (MCCB)
• Amperage rating: 400 A
• Voltage rating: 600 V
• Number of poles: 3
• Mounting style: Plug-in
• Application: Branch circuit overcurrent and short-circuit protection

Why this model stands out: designed for straightforward upgrades and reliable protection, the MJA36400 slots directly into compatible Square D panels, delivering quick installation without compromising safety or performance. The thermal-magnetic trip mechanism ensures predictable responses to overloads and faults, so downstream equipment such as motors, lighting, and feeders stay protected under normal operation and fault conditions alike. This is a practical choice for electricians and facility managers who value uptime, panel compatibility, and consistent protection in demanding environments.

Use cases and installation considerations

• Ideal for replacing worn or failing breakers in existing Square D panelboards and load centers, where a direct plug-in fit saves time and reduces labor costs.
• Suitable for three-phase commercial applications and light industrial installations requiring 400 A feeder or branch-circuit protection at up to 600 V.
• Excellent for panel modernization projects where OEM compatibility and reliable trip performance are priorities.

Stocked by AmpState, the Square D MJA36400 delivers high-capacity protection with straightforward plug-in installation, helping you keep critical electrical infrastructure safe, compliant, and up to code.