Square D QOU390 - 90 A, 240 V, 3-Pole Bolt-On Circuit Breaker | AmpState

Square D QOU390 is a 90A, 240V, 3-pole bolt-on molded case circuit breaker engineered for dependable branch circuit overcurrent and short-circuit protection in panelboards and loadcenters.

• Secure bolt-on mounting delivers a rigid, vibration-resistant bus connection, helping maintain consistent electrical performance in busy panels.
• Thermal-magnetic trip unit provides stable, repeatable protection across varying loads and ambient temperatures, reducing nuisance trips while safeguarding your circuits.
• OEM-compatible design is sized to work with matching Square D OEM loadcenters and panelboards for effortless integration.
• Broad suitability ideal for residential, commercial, and light industrial installations where reliable protection matters.

Technical at a glance

• Manufacturer: Square D
• Part Number: QOU390
• Type: Thermal-magnetic molded case circuit breaker
• Amperage Rating: 90A
• Voltage Rating: 240V
• Number of Poles: 3
• Mounting Style: Bolt-on
• Application: Branch circuit overcurrent and short-circuit protection

Use cases and benefits

In residential setups, the QOU390 protects feeders and branch circuits powering HVAC, water heating, and high-demand appliances, while maintaining safety and reliability. In commercial environments, it safeguards lighting, outlets, and critical equipment, ensuring quick, predictable responses to faults. For light industrial applications, this breaker offers robust protection for small machinery and control circuits, where stable trips and secure mounting make a difference in uptime.

Why this bolt-on design matters

Compared with non-bolt-on alternatives, the dedicated bolt-on mounting of the QOU390 creates a solid mechanical connection that resists vibration and reduces potential loosening over time. The combination of a thermal-magnetic trip provides fast fault response with consistent performance, so you can count on protection when it matters most.

Installation and compatibility tips

Ensure compatibility with your Square D OEM panelboard or loadcenter, and install per local codes and NEC guidelines. This unit is purpose-built for branch circuit protection and should be installed by a qualified electrician to maintain system safety and warranty integrity.

Ready to fortify your electrical system with proven Square D reliability? The QOU390 delivers precise protection, rugged mounting, and seamless integration for dependable performance across residential, commercial, and light industrial applications.