What it is and what it does
The Siemens 3VA1125-4GE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection in distribution panels. It carries a continuous 25 A at 40 °C and derates only slightly — still 24 A at 60 °C — so it holds its rating across typical enclosure ambient temperatures. The TM220 thermal-magnetic release handles overloads and short-circuits without an external trip unit. Four poles make it suitable for three-phase plus neutral or dual-supply configurations.
Breaking capacity — what the numbers mean
This MCCB interrupts 121 kA at 240 V, 75.6 kA at 415 V, and still clears 11.9 kA at 690 V. Those are the maximum fault currents it can safely break at each voltage level — critical for sizing upstream protection and verifying the installation's available fault current stays within the device's rating. The 690 V figure (11.9 kA) is the same as at 500 V, so it handles high-voltage low-fault scenarios consistently.
Panel fit and integration
Dimensions are 130 mm high, 101.6 mm wide, 70 mm deep — a standard SENTRON 3VA footprint that fits most DIN-rail or screw-mount panel layouts. IP40 on the front means it's protected against tools and small wires but not sealed against moisture; mount it inside a cabinet with a door. Rated insulation voltage is 800 V, so it's fine for 480/277 V and 600 V systems with margin.