Square D QO340 - 40 A, 240 V, 3-Pole Plug-In Circuit Breaker | AmpState

Meet dependable, site-ready protection for your electrical backbone with the Square D QO340 — a 40 A, 240 V, 3-pole plug-in circuit breaker designed for fast, reliable protection in panelboards and load centers. Built to simplify maintenance and reduce downtime, this molded case breaker delivers precise, repeatable protection for demanding residential, commercial, and light industrial circuits.

Why this breaker stands out

• Fast plug-in connection: A streamlined plug-in design speeds installation and simplifies replacement, so downtime is minimized during service or upgrades.
• Thermal-magnetic trip unit: The combination of a thermal element for overload protection and a magnetic trip for short circuits provides stable, repeatable protection performance across varying loads and conditions.
• 3-pole, 240 V configuration: Ideal for 3-phase panelboards and 240 V feeders, enabling safe, coordinated protection for larger or multi-wire circuits.
• OEM-compatible: Specifically designed to pair with matching Square D OEM load centers and panelboards, ensuring consistent performance and straightforward compatibility during panel upgrades or maintenance.
• Molded case, plug-in design: Durable construction with a clean, tool-free connection that reduces wiring errors and simplifies field service.

Who benefits most

• Electrical contractors and maintenance techs working on residential service upgrades, light commercial installations, or small industrial feeders.
• Projects requiring reliable 40 A protection on 240 V multi-wire or three-phase circuits, where quick swap-in replacement minimizes downtime.
• Panels that demand easy compatibility with OEM load centers and straightforward, plug-in installation.

Practical applications and use cases

Use the QO340 to protect branch circuits in panelboards and load centers where a 40 A, 240 V, 3-pole plug-in breaker is appropriate. It’s well-suited for 3-phase motor circuits, large lighting feeders, or other 240 V equipment in light commercial settings, as well as residential environments with multi-wire branch circuits that require coordinated protection.

Technical snapshot

• Manufacturer: Square D
• Part Number: QO340
• Type: Thermal-magnetic molded case circuit breaker
• Amperage Rating: 40 A
• Voltage Rating: 240 V
• Number of Poles: 3
• Mounting Style: Plug-in
• Application: Branch circuit overcurrent and short-circuit protection

Tips for maximizing performance

• Ensure your panelboard is rated for QO-series plug-in breakers to maintain system coordination and warranty integrity.
• Plan circuit layouts with the 3-pole configuration in mind for balanced power distribution in three-phase or multi-wire setups.
• During service, use the plug-in design to minimize downtime and simplify future replacements or upgrades.
• Pair with compatible OEM components to maintain consistent trip curves and protection characteristics across the entire panel.

Explore reliable, factory-backed protection with the Square D QO340 40 A, 240 V, 3-Pole Plug-In Circuit Breaker from AmpState — built to safeguard your circuits while keeping installation straightforward and maintenance manageable.