What it is and what the ratings mean
The Siemens 3VA1125-4EF32-0JA0 is a 3-pole molded case circuit breaker (MCCB) from the 3VA1 series, built on an IEC frame 160. Its headline breaking capacity is Icu=36kA at 415V AC — that rating means it can safely interrupt a fault current of up to 36,000 amps without welding its contacts or rupturing the case, which is the Class S (standard) level for this frame size. The thermal-magnetic trip unit (TM240) provides overload protection adjustable from 18A to 25A (Ir) and short-circuit protection adjustable from 6.4x to 12.8x In, so you set the actual pickup to match your downstream cable and load, not just the breaker's nominal rating. The shunt trip (STL) operates on 110-127V DC or AC 50/60Hz — a remote trip signal from an emergency-stop circuit or a safety PLC can drop the breaker without an operator at the panel. The nut keeper kit holds the terminal hardware in place during installation, a small detail that saves time on a crowded DIN-rail or panel-mount layout.
Where it fits in the panel
Mounts on a DIN rail or directly to a panel backplate using the frame 160 footprint. The 3-pole configuration with shunt trip occupies roughly the same width as a standard 3-pole MCCB in this frame class — plan for the shunt trip wiring (110-127V) to run back to the control transformer or safety relay, not through the breaker's load-side conductors. The nut keeper kit is already included, so no separate hardware order for the terminal connections.