What this MCCB is and what it protects
The Siemens 3VA1125-5EF42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 25 A continuous at 40 °C, configured as a 4-pole unit with a TM240 thermal-magnetic overcurrent release. It is designed for line protection — meaning it sits at the feeder or main distribution point in a panel, not on a specific motor or load branch. The 187 kA breaking capacity at 240 V AC tells you this breaker can safely interrupt a fault current up to that level without venting or cascading damage upstream, which matters when the available fault current at the panel is high — typical in industrial switchboards or transformer-fed distribution.
Breaking capacity across voltages — what it means for your system
This MCCB's interrupting rating varies by system voltage: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V and 690 V. The drop at higher voltages is typical for a thermal-magnetic breaker — the arc-quenching physics limits the interruptible current as voltage rises. For a 400 V or 480 V distribution panel, the 121 kA or 75.6 kA figure still covers most industrial fault levels. At 690 V, the 17 kA rating is adequate for lower-fault installations like some renewable or marine systems. Always verify the available fault current at the point of installation against the applicable voltage column.
Thermal derating — the real-world current you can carry
The 25 A rating holds steady from 40 °C through 50 °C ambient. At 55 °C it derates to 24 A; at 65 °C to 23 A; at 70 °C it still carries 23 A. That means in a warm panel — say 50 °C internal ambient — you can load this breaker to its full 25 A nameplate without derating. Above that, the thermal element in the TM240 release starts to trip earlier, so continuous load should be capped at the derated figure. The maximum power loss is 8.5 W, which is modest for a 4-pole 25 A MCCB and won't drive significant heat into the enclosure.
Panel fit and mounting
Dimensions: 130 mm height, 101.6 mm width, 70 mm depth. IP40 on the front.