What this MCCB is and where it fits
The Siemens 3VA1125-4EF32-0KH0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels and industrial switchboards. It carries a rated current of 25 A at 40 °C ambient, with a 3-pole configuration that suits three-phase feeder circuits, motor branch circuits, or main incomer duty in smaller sub-distribution boards. The breaking capacity is 121 kA at 240 V AC, dropping to 75.6 kA at 415 V and 52.5 kA at 440 V — figures that give solid fault-clearing headroom for most low-voltage commercial and light industrial installations. At 690 V it still interrupts 11.9 kA, covering 690 V line-to-line systems where available. Rated insulation voltage is 800 V, which means the internal clearances and creepage distances are designed for 690 V systems with margin. The maximum power loss is 8.5 W, a figure to factor into enclosure thermal calculations when grouping several breakers.
What the ratings mean for fit
The 25 A rating holds across 40 °C to 50 °C ambient without derating — at 55 °C it drops to 24 A, at 65 °C to 23 A, and at 70 °C still 23 A. That thermal profile means it can be installed in a moderately warm enclosure without losing capacity, but if the panel ambient runs above 50 °C, the continuous load must be reduced accordingly. The auxiliary switch configuration is 2 auxiliary switches plus 1 trip alarm switch (HQ), and the breaker includes a shunt trip release (STL). That gives remote tripping capability and status feedback — useful for emergency-stop circuits or PLC-based monitoring where the breaker position needs to be known in the control system. A trip indicator and voltage trigger are present, so the breaker provides local visual indication of a trip event. There is no undervoltage release, no ground-fault monitoring, and no communication function — this is a straightforward thermal-magnetic line-protection breaker, not a metering or communicating device.
Lifecycle and sourcing reality
The operating temperature range is -25 °C to +70 °C, with storage from -40 °C to +80 °C. That covers most indoor and sheltered outdoor installations, though the lower operating limit means it should not be relied upon for switching at sub-freezing temperatures without verifying the mechanism's performance. Dimensions are 130 mm height, 76.2 mm width, 70 mm depth — a compact footprint that fits standard Siemens 3VA panel cutouts and busbar systems. The width is exactly 3 inches (76.2 mm), which matches the typical 3-pole MCCB mounting pitch in most distribution boards.