The LV839063 is a Masterpact MTZ3 50 HF switch disconnector — a 5000 A continuous-rated, 4-pole drawout unit built for ANSI distribution applications. It's the main disconnect in a low-voltage switchgear lineup, sized for a 5000 A bus at 40 °C ambient. The drawout cradle means you can rack the cassette out for inspection or swap without de-energizing the bus, which keeps maintenance windows short on a critical feeder. At 40.5 in wide × 18.8 in tall × 16.8 in deep, it needs a full-height switchgear compartment — this isn't a panelboard breaker. The 9.06 in connection pitch matches standard ANSI bus spacing, so it retrofits into existing Masterpact drawout cubicles without re-drilling the bus bars.
The interrupting rating hits 100 kA Icu at 254 V AC and 508 V AC, and 85 kA Icu at 635 V AC — all with an external relay per ANSI C37.50. The 85 kA short-time withstand (Icw) for 1.5 s lets you coordinate downstream breakers: the MTZ3 holds in for that duration so a feeder breaker clears the fault, keeping the main bus online. If the switchgear room runs hotter, you'd need to consult the thermal derating curve, but for a typical 40 °C switchgear lineup this is the nameplate number for sizing the bus and cable connections.