What this MCCB is and what it does
The Siemens 3VA1225-6EF32-0KH0 is a SENTRON molded case circuit breaker (MCCB) built for line protection in distribution panels. Rated 250 A continuous current across three poles, it carries a TM240 thermal-magnetic overcurrent release — the thermal element handles overloads, the magnetic element clears short-circuits. The key number for a sourcing decision is the breaking capacity: 220 kA at 240 V and 154 kA at 415 V, which means it can safely interrupt fault currents up to those levels without failing catastrophically or cascading upstream. That kind of headroom is what you spec when the available fault current at the panel is high — a main breaker in a large industrial distribution board, for instance. The IP40 front protection keeps dust and small tools out of the breaker face in a clean indoor enclosure.
Current derating and thermal management
This breaker holds its full 250 A rating up to 50 °C ambient. Above that, it derates: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If the panel sits near a heat source or in a hot environment, the actual continuous current the breaker can carry is lower than the nameplate. The operating temperature range is -25 °C to 70 °C; storage goes from -40 °C to 80 °C. That storage range matters if the part sits in a spares crib for a while before installation — it can handle the cold warehouse.
Auxiliary contacts and shunt trip
The breaker ships with 2 auxiliary switches and 1 trip alarm switch (HQ type). These are wired into the control circuit for status feedback — the aux contacts signal open/closed, the alarm contact trips on a fault. A shunt trip release (STL) is integrated for remote tripping via a control signal. No undervoltage release or communication module is fitted on this variant. If remote monitoring or a UVR is needed, the order code would differ. The auxiliary trip module carries its own order code 3VA9688-0BL33 — that's the internal accessory, not a separate breaker.
Physical fit and panel integration
Dimensions: 105 mm wide, 158 mm high, 70 mm deep. That width is a standard 3-pole MCCB footprint — it fits a typical panel cutout or DIN-rail adapter for the SENTRON range. The 70 mm depth means it doesn't protrude far into the enclosure, leaving room for wiring ducts or busbars behind it. The reference code per DIN EN 81346-2 is Q — that's the switching-device function code for panel labeling.
Breaking capacity at different voltage levels
The interrupting rating varies significantly with system voltage. At 240 V it's 220 kA; at 415 V it drops to 154 kA; at 440 V it's 36 kA; at 690 V it's 17 kA. The 415 V figure is the one most relevant for a 400 V three-phase industrial panel in Europe or Asia — 154 kA is very high, suitable for a main breaker close to a large transformer. The 440 V and 690 V ratings matter for marine or heavy industrial systems where the line voltage is higher. Always match the available fault current at the installation point to the appropriate voltage column.
Endurance and trip indication
Latching endurance is rated at 15,000 operations. A trip indicator and voltage trigger are built in.