What the 250 A rating means for your panel
The Siemens 3VA1225-4GF42-0JH0 is a SENTRON molded case circuit breaker (MCCB) rated at 250 A continuous, per the datasheet, across a 4-pole configuration. That 250 A holds at 40 °C, 45 °C, and 50 °C without derating; at 55 °C it drops to 243 A, at 60 °C to 237 A, at 65 °C to 230 A, and at 70 °C to 223 A — so if your enclosure runs hot, the actual continuous current capacity is lower than the nameplate. The breaker is designed for line protection, meaning it sits at the incoming feeder or main distribution point, not downstream branch circuits.
Breaking capacity across voltage levels
The interrupting rating varies significantly with system voltage: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, 17 kA at 500 V, and 11.9 kA at 690 V. For a 480 V panel (common in North America), the relevant figure is the 440 V or 500 V value — 52.5 kA or 17 kA respectively — so verify your available fault current against the correct voltage column. The rated insulation voltage is 800 V, which covers 690 V systems with margin.
Physical fit and auxiliary options
Dimensions are 70 mm deep, 140 mm wide, 158 mm high. This is a panel-mount MCCB, not a DIN-rail unit — plan for bolt-on busbar connections and a cutout in the mounting plate. The breaker ships with a shunt trip (STL) auxiliary release and a complement of 2 auxiliary switches plus 1 trip alarm switch (HQ designation). A voltage trigger is present; undervoltage release is not included. The trip indicator is mechanical, visible on the front face.