The LV839336 is a MasterPact MTZ3 cradle — the drawout chassis that receives the breaker mechanism in a fixed installation. Rated for 4000 to 6000 A at 104 °F (40 °C), it carries the full continuous current of the largest MTZ3 frames. Three-pole configuration, UL/ANSI listed, so it lands directly into North American switchgear assemblies without a separate UL file chase.
What the cradle does in the panel
The cradle is the stationary half of a drawout breaker system. It bolts into the switchgear cubicle and provides the primary disconnects, secondary control wiring terminals, and the racking mechanism that moves the breaker between CONNECT, TEST, and DISCONNECT positions. For a panel builder, the cradle defines the cutout and bus connection pattern — once it's installed, the breaker itself swaps in and out without disturbing the main bus.
Key rating — what 4000-6000 A means
The 4000 to 6000 A rated operational current (Ie) at 40 °C ambient is the cradle's continuous current capacity, not the breaker's interrupting rating. It means the cradle's primary disconnects and bus connections are sized to carry that full current without exceeding temperature rise limits. The breaker inserted into this cradle determines the interrupting capacity (kAIC) and the protection settings. For a site electrical engineer coordinating selectivity, the cradle's continuous rating sets the upper bound of the main bus section it serves.