Line protection MCCB, 250 A, 4-pole — what the ratings mean for fit
The Siemens SENTRON 3VA1225-6GF42-0AC0 is a 4-pole molded case circuit breaker (MCCB) rated for 250 A continuous current, designed for line protection in distribution panels. Its interrupting capacity is 220 kA at 240 V AC, 154 kA at 415 V, and still 17 kA at 690 V — meaning it can clear high-fault currents on the secondary side of a large transformer without cascading upstream. The TM240 thermal-magnetic release provides fixed thermal and magnetic trip settings, so it is a straight swap for an existing 250 A line feed; no adjustment needed at commissioning. At 40 °C ambient the breaker carries the full 250 A without derating; at 55 °C it still holds 243 A, and at 70 °C it is rated 223 A. That thermal curve means the part can be installed in a warm enclosure — say a non-ventilated panel near a drive cabinet — and still deliver near-rated current. The 57 W maximum power loss at full load should be factored into the enclosure's thermal budget, but it is typical for a 250 A frame.
Mounting dimensions and panel integration
The breaker measures 140 mm wide, 158 mm high, and 70 mm deep. The 4-pole width (140 mm) matches the standard SENTRON 3VA frame footprint for a 250 A unit — it occupies the same DIN-rail or screw-mount positions as other 3VA1 breakers of the same rating. Depth of 70 mm leaves clearance for rear-connected busbars or cable lugs inside a typical 200 mm deep enclosure.