Schneider Electric QMB366MW Panelboard Switch

Schneider Electric's Square D QMB366MW Fusible Main Switch Replacement Unit is a three-pole, 600 A, 600 V AC fusible main switch designed as a replacement for QMB fusible panelboards. It provides overcurrent and short-circuit protection, a disconnect between source and load, and a circuit-open/close function in a single module, consolidating protection and switching for service-entry applications. The QMB366MW is intended for use within QMB panelboard interiors and supports the QMB switch family; these switches are rated to accept Class H, Class R, or Class J fuses up to 600 A, with Class L fuses used for ratings above 600 A (601–800 A). This unit carries a 200 kA symmetrical interrupt rating, making it suitable for heavy-duty isolation of faults. As a replacement unit, it aligns with Schneider Electric's main switch replacement catalog, and the interior arrangement includes factory-mounted mounting on the bus assembly while not back-feeding the branch switch. In service-entry installations, the QMB fusible panelboard solution provides both protection and isolation for the panel's load side, making the QMB366MW a purpose-built main switch for high‑current, high‑voltage distribution systems.