What this MCCB carries — and where the ratings matter
The Siemens 3VA1225-5EF32-0DH0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in distribution panels. Its 250 A rated continuous current (Iu) holds flat from 40 °C to 50 °C, then derates to 223 A at 70 °C — so the thermal curve stays full-rated in a ventilated enclosure but needs headroom if the panel runs hot. The TM240 thermal-magnetic release handles overload and short-circuit protection without an electronic trip unit, keeping the design simple and field-replaceable. Breaking capacity is the headline: 187 kA at 240 V, 121 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V. At 415 V — common for industrial three-phase — 121 kA means this breaker can interrupt a fault current that high without upstream fuses or a current-limiting reactor. That is the spec that decides whether it coordinates with the transformer or main breaker in a selective coordination study. Three poles, 800 V rated insulation voltage (Ui). The auxiliary contact block is factory-configured as 2 auxiliary switches plus 1 trip alarm switch (HQ variant), and an undervoltage release (UVR) is built in — so it drops the load on loss of control voltage without a separate relay. Latching endurance is rated at 15 000 operations, which is typical for a panel main or feeder breaker that sees infrequent switching.
Panel fit and mounting
Dimensions: 105 mm wide, 158 mm high, 70 mm deep. The 105 mm width is a three-pole MCCB standard footprint — it occupies three 35 mm DIN-rail modules side by side. Depth of 70 mm leaves clearance for rear-mounted busbars or a gland plate behind the DIN rail. Front protection is IP40, so it is suited for enclosed distribution boards but not washdown zones.