BQ3B040

The Siemens BQ3B040 is a ‑pole,  amp thermal‑magnetic molded‑case circuit breaker in Siemens’ BQ series, designed for reliable overcurrent protection in low‑voltage AC electrical distribution systems. Intended for use in panelboards that accept bolt‑on style breakers, the BQ3B040 is engineered for 120/240 VAC service and protects two ungrounded conductors simultaneously. Its ‑pole configuration provides common‑trip protection, meaning both poles will open together on overload or fault, which is essential for compliance with NEC requirements and safe operation of multi‑wire branch circuits.

Electrically, the BQ3B040 incorporates a thermal‑magnetic trip unit that combines heat‑sensitive overload protection with a magnetic instantaneous element to rapidly clear short‑circuit faults. It is UL 489 listed and carries a {aic rating} interrupting capacity, allowing it to safely interrupt fault currents up to in appropriately designed systems. This makes it suitable for general branch‑circuit applications such as lighting, receptacles, HVAC controls, and small motor loads in residential, commercial, and light industrial environments where dependable overcurrent protection is required.

Mechanically, the breaker features a rugged molded case with a manual toggle actuator for ON/OFF switching and reset after a trip event. The bolt‑on mounting ensures a secure connection to the panelboard bus, and the breaker accepts standard conductor sizes compatible with Siemens panel wiring (e.g., #14 – #4 AWG copper or aluminum, per panelboard rating). Its design and wide availability make the BQ3B040 a practical choice for both new installations and retrofit replacements, offering consistent performance with Siemens’ established quality and compliance with UL/CSA safety standards.

Purchase the BQ3B040 at Electrical.com, your reliable partner for industrial and commercial electrical products. Our selection includes circuit breakers, panel boards and accessories from manufacturers like Siemens, backed by a dedicated sales team ready to assist with technical questions, product selection, and support.