MCCB for 250 A feeder protection
The Siemens 3VA1225-4EF32-0BH0 is a SENTRON molded case circuit breaker rated for 250 A continuous current (Iu) at 40 °C, with a TM240 thermal-magnetic overcurrent release. Its interrupting capacity reaches 121 kA at 240 V and 75.6 kA at 415 V, so it handles high-fault scenarios typical of industrial distribution panels without cascading upstream. This 3-pole unit is configured for line protection — no ground-fault monitoring, no communication module — and includes an undervoltage release (UVR) plus a 2-auxiliary + 1 trip-alarm switch block. The front face carries IP40 protection, suitable for enclosed panel mounting.
Current derating and thermal limits
The breaker holds its full 250 A rating up to 50 °C ambient. Above that, it derates linearly: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. For a panel with internal temperature rise near the upper limit, the effective continuous current drops — plan the load accordingly.
Mounting and integration
Dimensions are 105 mm wide, 158 mm high, and 70 mm deep — a standard 3-pole MCCB footprint for DIN-rail or screw-mount panel installation. The 70 mm depth fits typical distribution board gutters without crowding the gland plate.