What this MCCB is and where it fits
The Siemens 3VA1125-4EF32-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels and motor control centers. Its 3-pole construction and 25 A rating at 40 °C make it a fit for feeder circuits, lighting panels, and light industrial loads where the TM240 thermal-magnetic release provides inverse-time overload and instantaneous short-circuit protection. The 121 kA breaking capacity at 240 V gives substantial fault-current headroom for high-available-fault installations — the kind of SCCR you need when the transformer is close and the bus is stiff.
Breaking capacity across voltages — what the ratings mean
This MCCB carries a 121 kA interrupting rating at 240 V, dropping to 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at both 500 V and 690 V. The steep derating above 440 V is typical for a compact-frame MCCB — at 690 V the 11.9 kA figure still covers most industrial motor branch circuits, but you need to verify it against the available fault current at that voltage. The 800 V rated insulation voltage confirms the breaker is physically built for 690 V systems even if the interrupting rating is lower there.
Thermal derating and ambient temperature
The 25 A rating holds flat from 40 °C through 50 °C, then steps down to 24 A at 55–60 °C and 23 A at 65–70 °C. That means in a warm enclosure — say 55 °C ambient — you lose only 1 A of headroom. The operating range spans -25 °C to 70 °C, with storage from -40 °C to 80 °C. The 8.5 W maximum power loss is manageable in a standard panel, but if you are ganging multiple breakers in a sealed enclosure, account for the cumulative heat.
Physical fit and panel integration
Dimensions are 130 mm height, 76.2 mm width, 70 mm depth — a compact 3-pole footprint that fits standard MCCB mounting bases in SENTRON and third-party distribution panels. The IP40 protection on the front means it is dust-protected but not sealed against water ingress; install in a dry indoor enclosure. No undervoltage release, no shunt trip, no communication module on this variant — it is a straight thermal-magnetic line-protection breaker with no auxiliary accessories built in.