Breaking capacity and what it means for your fault-current study
The Siemens 3VA1125-5EF36-0AE0 is a 3-pole SENTRON molded case circuit breaker rated for 25 A continuous current with a TM240 thermal-magnetic release. Its interrupting capacity hits 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 690 V — that 187 kA figure at 240 V means it can safely clear a fault right at the secondary of a large distribution transformer without the arc re-striking. The 121 kA at 415 V is the number most panel builders will check first for IEC 60947-2 coordination studies; if your available fault current at the line side exceeds that, you need a current-limiting upstream device or a higher-rated frame.
Thermal derating and panel fill
The breaker carries the full 25 A from 40 °C through 50 °C ambient, then derates to 24 A at 55 °C, 23.5 A at 60 °C, 23 A at 65 °C, and 22.5 A at 70 °C. That flat 25 A band up to 50 °C is useful for a panel running warm but not hot — you don't lose headroom until the enclosure ambient climbs above 50 °C. The 70 mm depth and 76.2 mm width fit the standard SENTRON 3VA mounting footprint; four HQ auxiliary switches are built in, so you get status feedback without adding a separate accessory block.