What you're specifying
The LV839307 is a MasterPact MTZ3 drawout air circuit breaker — 3-pole, 4000 A continuous rating at 40 °C, with H2 breaking capacity delivering 85 kA Icu at 508 VAC (also 85 kA at 254 VAC and 635 VAC per ANSI C37.50). This is the frame and mechanism only: it ships without a Micrologic trip unit, so you'll need to order the protection relay separately. The ArcBlok arc-extinction chamber is integral. Drawout mounting means this breaker slides into a cradle — no hard wiring for the main power connections during swap-out. Rated short-time withstand (Icw) is 85 kA for 0.5 s, which gives you selectivity headroom downstream. Mechanical durability is 5000 cycles; electrical durability 1000 cycles per ANSI C37.50.
Breaking capacity — what it means for coordination
The H2 code tells you the interrupting rating: 85 kA Icu at 254 V, 508 V, and 635 V AC. That's a flat 85 kA across the full ANSI voltage range, not a derated curve. For a 4000 A main breaker feeding a switchboard, that SCCR covers most industrial service-entrance and distribution applications without cascading upstream. Maximum breaking time is 25 to 30 ms; maximum closing response time is 70 ms. The 85 kA Icw for 0.5 s supports delayed tripping for selective coordination with downstream feeders — you can let a fault ride through on the feeder breaker without pulling the main.
The drawout chassis measures 31.07 in wide by 18.8 in high by 16.8 in deep, with a connection pitch of 9.06 in (230 mm) between phase centers. Mounting is on base plate rails — this is a floor-mount switchgear frame, not a DIN-rail clip. Verify your cell opening and bus bar spacing before committing the cutout.