Molded case switch for feeder isolation and fault protection
The Siemens 3VA4110-1BB34-3AA0 is a 3-pole molded case switch (MCS110) on a UL frame 125, rated 100 A continuous. This is a switch, not a breaker: no overload protection built in, so it serves as a disconnect or feeder isolator where overcurrent protection is handled separately downstream.
Self-protection and coordination
The self-protection setting Ii = 16 x In (1600 A instantaneous pickup) means the switch will trip magnetically on a hard short but will not respond to overloads. That makes it a clean fit for a motor feeder or transformer primary where the downstream device (a motor starter or secondary breaker) handles the overload curve, and the switch only sees fault currents. Pair it with a 100 A rated fuse or breaker upstream for full selectivity.