The LV839057 is a Masterpact MTZ3 40 HF switch disconnector rated for 4000 A at 104 °F (40 °C) — that's the continuous current it carries without derating in a typical 40 °C ambient panel. The 100 kA Icu at 254 V AC (and 508 V AC, with 85 kA at 635 V AC) tells you the maximum fault current it can safely interrupt once, per ANSI C37.50. That 100 kA figure governs your upstream fault-duty coordination: if your service entrance or switchgear bus can deliver 100 kA symmetrical at 254 V, this breaker holds the line without cascading. The 85 kA Icw for 1.5 seconds (ANSI C37.50) is the short-time withstand — it lets the breaker ride through a delayed trip coordination window, holding closed while downstream devices clear a fault. That matters for selective coordination in a distribution panel: you can set the trip delay long enough to let a feeder breaker clear first, without the main tripping.
Drawout chassis integration
Drawout mounting means the breaker mechanism slides out of its chassis for maintenance or swap without disturbing the line and load connections. The chassis mounts on a support frame, with a connection pitch of 9.06 in (230 mm) between phases. Overall footprint: 31.07 in wide × 18.8 in high × 16.8 in deep (789 × 478 × 427 mm). That depth includes the drawout travel — verify your enclosure depth allows full rack-out clearance before committing the panel layout.