Square D MJL36400 - 400 A, 600 V, 3-Pole Circuit Breaker | AmpState

Engineered for dependable branch circuit protection, the Square D MJL36400 is a 400 A, 600 V, 3-pole molded case circuit breaker designed to guard panelboards and loadcenters against overcurrent and short circuits. Its compact molded-case form frees up valuable space in crowded electrical panels while delivering precise, repeatable performance when protection is needed most.

Why this breakers stands out

• Space-efficient molded-case design maximizes panel capacity, making room for future circuit additions without compromising protection.
• Thermal-magnetic trip unit provides stable, repeatable protection by responding to both overload and short-circuit conditions with fast, predictable trips.
• Three-pole configuration ideal for 3-phase systems common in commercial and light industrial environments, while still suitable for residential panel setups that require robust protection.
• OEM compatibility engineered to be compatible with matching Square D loadcenters and panelboards, ensuring a reliable fit and straightforward replacement or upgrade.
• Versatile application suitable for residential, commercial, and light industrial protection scenarios where steady, dependable performance matters.

Technical snapshot

• Manufacturer: Square D
• Part number: MJL36400
• Type: Thermal-magnetic molded case circuit breaker (MCCB)
• Amperage rating: 400 A
• Voltage rating: 600 V
• Poles: 3
• Application: Branch circuit overcurrent and short-circuit protection

Ideal use cases

• Upgrading or replacing protection in commercial panelboards and loadcenters that serve heavy equipment or multiple high-load circuits.
• Feeding 3-phase equipment in light industrial settings where reliable short-circuit protection is critical.
• Installing as a dedicated feeder breaker for main distribution panels in mid-size facilities, helping to prevent nuisance trips and maintain uptime.

How it delivers real value

The MJL36400 isn’t just a spec sheet entry—it’s a practical solution for engineers and electricians who demand predictable protection and panel efficiency. By combining a compact footprint with a dependable thermal-magnetic trip mechanism, this breaker protects valuable equipment while preserving panel space for future expansion. Its OEM compatibility means fewer compatibility concerns during installation, reducing the risk of misfits or incongruent trip curves.

Practical tips for installation and care

• Verify compatibility with your specific Square D loadcenter or panelboard model to ensure a seamless fit and correct bus alignment.
• Use in applications where 3-phase protection is required or where three-pole coverage is essential for balanced circuit protection.
• Schedule periodic visual inspections for signs of overheating or wear in the panel enclosure, and confirm that wiring terminations are tight to maintain reliable trips.
• Keep spare replacement units on hand for quick maintenance or capacity upgrades to minimize downtime.

Whether you’re upgrading an aging panel, designing a new electrical room for a light industrial environment, or provisioning a commercial panelboard for higher load demands, the Square D MJL36400 400 A, 600 V, 3-Pole Circuit Breaker delivers targeted protection with space-conscious design and dependable performance. Add it to your panel today to ensure robust, long-lasting circuit protection that aligns with your Square D ecosystem and installation standards.