What this MCCB carries and where it fits
The Siemens 3VA1225-4EF42-0CA0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current, 4-pole, configured for line protection with a TM240 thermal-magnetic overcurrent release. Breaking capacity runs from 121 kA at 240 V down to 11.9 kA at 690 V — high enough for most secondary distribution and large motor branch circuits where fault current is substantial. The 70 mm depth and 140 mm width fit standard SENTRON panel cutouts; verify the 158 mm height against your enclosure depth before committing the gland plate.
Breaking capacity — what the numbers mean for coordination
The 121 kA at 240 V is the highest interrupting rating on this unit, typical for 120/208 V wye secondary where available fault current can be severe. At 415 V it still holds 75.6 kA, enough for most European industrial grids. At 690 V the rating drops to 11.9 kA — still serviceable for 690 V motor circuits but you'll want to verify the upstream transformer impedance keeps prospective fault below that. The 25 kA at 440 V is the figure to use for North American 480 V systems. These are Icu (ultimate breaking capacity) values; the MCCB is rated to interrupt once at these levels and remain functional afterward.
Thermal derating — the real continuous current in a warm panel
Rated 250 A continuous up to 50 °C ambient. Above that the TM240 release 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. If your panel ambient runs 55 °C or higher — common in tightly packed MCC sections or outdoor enclosures — size upstream conductors and downstream load for the derated figure, not the nameplate 250 A. The operating temperature range is -25 °C to 70 °C, storage -40 °C to 80 °C.
What's on the nameplate — traceability checkpoints
Brand SENTRON, product designation molded case circuit breaker, version line protection. Four poles, 250 A continuous, rated insulation voltage 800 V. TM240 release means the thermal element is calibrated for 240 A frame — the 250 A continuous rating is the maximum for this frame size. Undervoltage release is built in; no auxiliary contacts, no communication module, no ground fault monitoring, no voltage trigger, no phase failure detection. IP40 on the front — suitable for enclosed panel mounting, not for washdown or outdoor exposure without an additional enclosure.