Siemens NSB B320 Miniature Circuit Breaker

Siemens NSB B320 Miniature Circuit Breaker is a 20 A, 3-pole device rated for 240 V AC with a 10 kA short-circuit interrupt rating, belonging to Siemens’ BL family of low-voltage molded-case breakers. Designed for three-phase protection in electrical panels or switchgear, it provides thermal-magnetic trip protection against overloads and short circuits in distribution circuits. The B320 is cataloged as a 20 A, 240 V, 3-pole model and is widely stocked by distributors for industrial and commercial installations needing reliable three-phase overcurrent protection. Typical applications include protection of feeders and branch circuits in commercial facilities and light industrial equipment operating at 240 V three-phase service, with robust 10 kA interrupt performance at 240 V AC. As part of Siemens' molded-case family, the B320 emphasizes consistent operation within standard low-voltage distribution systems and is compatible with panelboard configurations that use 240 V three-phase supplies. Major distributors such as Grainger and Zoro list the B320 with the same ratings, confirming its role as a standard 20 A, 3-pole device in many electrical rooms.