Siemens NJG4B400 Circuit Breaker

Siemens NJG4B400 is a four-pole molded‑case circuit breaker from the NJG4 family, engineered to protect heavy‑duty, four‑wire power distribution sections in industrial and commercial environments by interrupting fault current swiftly while protecting conductors and equipment. With a thermal‑magnetic trip mechanism integrated into a rugged molded‑case housing, it provides coordinated overload protection and fast short‑circuit clearing, making it a reliable choice for feeders, main breakers in switchgear, and panelboards in existing Siemens installations. The model is commonly referenced as NJG4B400 and is available in variants such as NJGA4 and NJG4B400L, the latter indicating lug‑terminated configurations that accommodate different bus and terminal layouts in control panels and switchgear. When selecting this device, confirm the exact electrical ratings—voltage, interrupting capacity, and trip characteristics—from the official Siemens documentation to ensure compatibility with your system’s voltage class, fault current level, and installation footprint.