What this breaker is and what the ratings mean
The Siemens 3VA1125-4EF42-0AA0-ZD00 is a 4-pole IEC frame 160 molded case circuit breaker with a 25 A rated current (In) and a breaking capacity class S giving Icu = 36 kA at 415 V AC. That 36 kA interrupting rating at 415 V means it can safely clear a fault up to 36,000 A without welding its contacts or rupturing the arc chamber — critical for panel SCCR compliance in industrial distribution. The TM240 thermal-magnetic trip unit provides adjustable overload protection (Ir) from 18 A to 25 A and adjustable short-circuit protection (Ii) from 6.4 to 12.8 times In, so you tune the trip curve to the downstream load without swapping the breaker body. This variant includes a nut keeper kit and is configured for DC Power OEM applications in China. The N conductor is unprotected — meaning the neutral pole is not switched or monitored by the trip unit, which is standard for 4-pole breakers used in TN systems where the neutral is solidly grounded and only the phases need overcurrent protection.
Deployment context
Mounts in a standard panel enclosure on a DIN rail or directly to a backplate via the frame mounting points. The 4-pole configuration suits three-phase plus neutral distribution in industrial switchboards, motor control centers, or OEM machinery where the 25 A rating covers branch circuits feeding small motors, lighting, or control transformers. The nut keeper kit simplifies captive hardware handling during panel assembly.