What this MCCB carries — and what it means for your panel
The Siemens 3VA1225-4EF42-0CH0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current (Iu) with a TM240 thermal-magnetic release — the thermal element handles overloads, the magnetic element handles short-circuits, and the 240 designation means the thermal pickup is calibrated for a 240 A frame. Four poles cover three-phase plus neutral (or a fourth phase), and the 121 kA breaking capacity at 240 V tells you it can interrupt a fault current up to that level without welding contacts or cascading failure upstream. At 415 V the interrupting rating drops to 75.6 kA, at 440 V to 25 kA, and at 690 V to 11.9 kA — the voltage derating is normal for MCCBs, so verify your available fault current at the actual system voltage before specifying. This is the line protection version (no ground-fault monitoring, no communication module, no voltage trigger), built for straightforward feeder or main breaker duty in distribution panels. The IP40 front protection means the breaker face is protected against solid objects over 1 mm, but the enclosure itself must provide the overall panel IP rating. Operating temperature spans -25 °C to 70 °C, with storage from -40 °C to 80 °C — fine for most indoor industrial environments.
Thermal derating and endurance — the real-world limits
The 250 A rating holds flat from 40 °C through 50 °C ambient. At 55 °C it derates to 243.3 A, at 60 °C to 236.5 A, at 65 °C to 229 A, and at 70 °C to 223 A. If your panel ambient runs above 50 °C, size the upstream conductor and downstream load for the derated value, not the nameplate 250 A. Mechanical endurance is rated at 15 000 operations — that's the latching mechanism life, not the electrical contact life under load, which will be lower depending on switching frequency and fault-clearing history.
Auxiliary contacts and undervoltage release — what's on board
Factory-fitted with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration) and an undervoltage release (UVR). The UVR trips the breaker when control voltage drops below a threshold — common for emergency-stop circuits or undervoltage protection schemes. The auxiliary contact set (2 NO/NC changeovers) reports breaker position; the trip alarm switch signals a fault trip separately from a manual open. The integrated auxiliary trip order code is 3VA9608-0BB24 if you need a replacement module.
Dimensions and panel fit
Width 140 mm, height 158 mm, depth 70 mm. Four-pole MCCBs at this frame size typically mount on a DIN rail or bolt directly to a backplate; the 140 mm width is the standard for a 250 A 4-pole SENTRON 3VA2 frame. Verify gland plate cutouts and busbar spacing against these dimensions before panel layout.