Square D MJ-860 - 40A, 240VAC, 3-Pole, Circuit Breaker

Meet the Square D MJ-860 40A, 240VAC, 3-Pole Circuit Breaker—a compact, dependable solution for protecting three-phase electrical systems. With a 40-amp rating at up to 240 volts, this 3-pole unit delivers reliable overcurrent protection in a wide range of industrial and commercial applications, including panelboards, switchboards, and control panels.

Key specifications

• Current rating: 40 A
• Voltage rating: 240 VAC
• Poles: 3-Pole
• Breaker type: Circuit Breaker
• Ideal for: industrial, commercial, and OEM panel configurations requiring dependable overcurrent protection in distribution panels and motor control centers

Why a 3-Pole design matters

For three-phase systems, the MJ-860 disconnects all conductors in unison. This coordinated trip minimizes the risk of unprotected phases, helps prevent equipment damage from phase imbalances, and supports compliance with safety standards in modern facilities.

Who should consider the MJ-860

• Facilities upgrading panelboards, switchboards, or control panels that demand robust, standalone branch-circuit protection
• OEMs incorporating reliable overcurrent protection into control enclosures and machinery
• Industrial and commercial environments where motor control centers rely on consistent, fail-safe protection

Practical usage and tips

Install the MJ-860 in compatible Square D wiring configurations where a 40-amp, 3-pole solution is required. Its design fits standard distribution equipment footprints, enabling straightforward integration and predictable performance under peak loads.

Why choose Square D MJ-860 over generic breakers

Designed specifically for three-phase applications, the MJ-860 provides coordinated protection across all phases, reducing nuisance trips and safeguarding motors and drives. Its 240 VAC rating covers a broad range of common industrial power supplies, while the 40 A rating aligns with typical equipment protection thresholds in medium-duty environments.