250 A MCCB with TM240 release — what the ratings mean for panel fit
The Siemens SENTRON 3VA1225-6GF42-0AG0 is a 4-pole molded case circuit breaker rated at 250 A continuous, with a TM240 thermal-magnetic overcurrent release. That TM240 designation means the thermal pickup is fixed at 240 A, so this breaker is sized for a 240 A nominal load path — not a general-purpose 250 A frame you can adjust down. The insulation voltage is rated at 800 V, which covers 480 V and 600 V class systems with headroom. Breaking capacity is what you check first for fault coordination. At 240 V this breaker interrupts 220 kA; at 415 V it's 154 kA; at 440 V it drops to 75.6 kA; at 500 V it's 30 kA; and at 690 V it's 17 kA. That steep derating curve means you need to confirm the available fault current at your actual system voltage — not just the highest number on the nameplate. Thermal derating matters for panel ambient. The breaker carries a full 250 A at 40 °C through 50 °C. At 55 °C it's 243 A; at 60 °C it's 237 A; at 65 °C it's 230 A; at 70 °C it's 223 A. If your enclosure runs hot — say a packed MCC lineup — that 223 A at 70 °C is the number to size against, not the 250 A sticker. The auxiliary switch configuration is 1 auxiliary switch plus 1 trip alarm switch (HP type). That gives you one N/O or N/C signal for breaker position and one dedicated signal that only changes state on a trip event — useful for remote fault annunciation without wiring through the position contact.
Lifecycle and compliance — active line, no obsolescence concern
Power loss at rated current is 57 W maximum. That's the heat you need to dissipate inside the enclosure — factor it into your thermal calculation, especially in a multi-breaker lineup where cumulative losses add up. Operating temperature range is -25 °C to 70 °C, with storage from -40 °C to 80 °C. The storage range exceeds the operating range — that's for shipping and warehousing, not running.
Dimensions and panel integration
The breaker measures 140 mm wide, 158 mm high, and 70 mm deep. That 70 mm depth is the projection behind the panel face — important for gutter space in a shallow enclosure. The 140 mm width for a 4-pole frame is standard for this class; verify your busbar or cable lug spacing accommodates the pole pitch before cutting the mounting plate.