What the ratings mean for fit
The Siemens SENTRON 3VA1225-6EF32-0DH0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection at 250 A continuous current (Iu). That 250 A holds flat from 40 °C to 50 °C ambient, then derates gradually to 223 A at 70 °C — so in a warm panel you still have headroom down to about 223 A before the TM240 thermal-magnetic trip unit starts to drift. The interrupting ratings climb steeply with voltage: 220 kA at 240 V, 154 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V. At 415 V, that 154 kA SCCR covers most industrial distribution transformers without needing a current-limiting fuse upstream. The insulation voltage (Ui) is rated 800 V, so it's suitable for 690 V line-to-line systems with margin.
Integration and panel fit
The breaker measures 105 mm wide × 158 mm high × 70 mm deep — a standard 3-pole MCCB footprint for the 250 A frame class. It mounts on a DIN rail or directly to a backplate via the four corner holes. The front face carries an IP40 protection rating, so it's fine for enclosed panels but not for washdown environments. The auxiliary contact block is configured as 2 auxiliary switches plus 1 trip alarm switch (HQ designation), wired via the integrated plug-in terminals. An undervoltage release (UVR) is fitted as standard — if the control voltage drops, the breaker trips immediately, which is useful for safety circuits or emergency-stop chains that need a loss-of-voltage disconnect.
Selectivity and coordination notes
The TM240 overcurrent release is a thermal-magnetic type — fixed thermal pickup for overloads, magnetic instantaneous for short-circuits. No electronic adjustment, no communication function, no phase-failure detection. That makes it a straightforward, field-reliable choice for distribution panels where you don't need remote monitoring or selective coordination curves. The trip indicator on the front gives a visual flag after a fault event, which speeds up troubleshooting on a multi-breaker lineup. Operating temperature range is -25 °C to 70 °C; storage from -40 °C to 80 °C.