Square D | CJ400NA | Circuit Breaker | 400A | 3-Pole | 600V | Bolt-On

Square D CJ400NA Circuit Breaker is a robust protective device designed for demanding 600-volt, three‑phase power networks. With a 400-amp rating and bolt-on mounting, this 3‑pole breaker is built for reliability in maintenance, retrofit, and replacement projects where exact specifications matter.

• Amperage: 400A
• Poles: 3-Pole
• Voltage: 600V
• Mounting: Bolt-On
• Part Number: CJ400NA

Why the CJ400NA stands out

Designed for secure, quick installation, the bolt-on construction provides a solid electrical and mechanical connection that resists vibration in demanding environments. The 3-pole design protects all three phases, delivering balanced protection for motors, feeders, and distribution circuits. A 600V maximum rating makes it suitable for many industrial and commercial installations, while the 400A capacity handles substantial loads without frequent tripping. Since this is a Square D part, it integrates with standard panels and bus configurations from the same family, simplifying replacements and upgrades.

Use cases: maintenance, retrofit, and replacement

This CJ400NA is ideal when you need a drop-in compatible protective device for aging equipment, panel upgrades, or service upgrades. Common scenarios include upgrading a 3‑phase feeder in a manufacturing line, replacing a failed breaker in a service panel, or retrofitting an older installation to meet newer electrical demands while preserving existing gear. It’s particularly well-suited for environments where reliable protection and fast, secure mounting are critical.

Fit, compatibility, and best practices

Notes: Confirm fit and ratings before ordering. The CJ400NA part number is the best reference for compatibility with your panel. To ensure a smooth replacement, verify that your enclosure supports bolt-on breakers of this style, and that the bus and mounting dimensions align with the CJ400NA specification. If in doubt, have your panel model and existing breaker reference handy during ordering.

Practical tips for installation and operation

Before installation, de-energize the equipment and follow your site safety procedures. Use the correct tools for bolt-on assemblies and torque to manufacturer guidelines. This breaker is designed to slot into compatible Square D panels, preserving coordinated protection across your distribution network. With proper installation, the CJ400NA delivers dependable overcurrent protection for critical loads while enabling straightforward service in the future.

Who benefits most

Maintenance teams, electrical contractors, and facilities engineers responsible for mid-to-large commercial or light-industrial power systems will appreciate the CJ400NA for its combination of robust protection, secure mounting, and clear compatibility references. If you’re upgrading distribution reliability in a 3‑phase 600V environment, this 400A, 3‑pole, bolt-on breaker is designed to pay off through reduced downtime and consistent performance.