Square D QO140 - 40 A, 120 V, 1-Pole Plug-In Circuit Breaker | AmpState

Meet the Square D QO140—a compact, reliable solution for protecting your 120-volt circuits. This 40 A, 1-pole plug-in molded case circuit breaker is engineered for dependable branch circuit overcurrent and short-circuit protection in panelboards and load centers, delivering peace of mind in homes, small businesses, and light industrial settings.

• Fast plug-in connection – Designed for quick installation and easy replacement, the QO140 snaps into compatible Square D QO load centers, minimizing downtime during upgrades or service calls.
• Thermal-magnetic trip for stable protection – Combines a precise thermal element with a magnetic trip for repeatable, accurate protection against overcurrent and short circuits, helping prevent damage to wiring and connected devices while reducing nuisance trips.
• 1-pole, 40A at 120V – Suitable for protecting a single 120V branch circuit with up to 40 amps of continuous load in a compact form factor that fits standard panel spaces.
• OEM-compatible and scalable – Built to align with the Square D QO series, ensuring seamless compatibility with matching OEM load centers and panelboards for a consistent electrical system.
• Versatile for multiple environments – Ideal for residential circuits, commercial lighting and receptacle runs, and light industrial applications where reliable protection is essential.

Technical specifications

• Manufacturer: Square D
• Part Number: QO140
• Type: Thermal-magnetic molded case circuit breaker
• Amperage Rating: 40A
• Voltage Rating: 120V
• Number of Poles: 1
• Mounting Style: Plug-in
• Application: Branch circuit overcurrent and short-circuit protection

Practical use and installation considerations

Use the QO140 to protect a dedicated 120V branch circuit within a Square D QO load center or panelboard. Its plug-in design simplifies swaps and upgrades, reducing service time and downtime for routine maintenance. When planning installation, confirm that your panel is part of the QO family and that the space is designated for a 1-pole, 40A breaker. Always follow local electrical codes and safety practices, de-energize the main service before work, and ensure the wiring gauge and connections align with 40A protection requirements. In everyday use, the thermal-magnetic trip helps you avoid nuisance trips from normal inrush while still delivering fast clearing on true faults.

Ideal for electricians, facilities managers, and DIY enthusiasts upgrading a panel or expanding a circuit. The QO140’s combination of quick installation, reliable protection, and OEM compatibility makes it a practical, long-term choice for safeguarding your electrical distribution without compromising panel performance.