What it is and what it does
The Siemens 3VA1125-5EF32-0AC0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in distribution panels. Rated continuous current Iu is 25 A at 40 °C, with a TM240 thermal-magnetic overcurrent release that handles the overload and short-circuit trip curve. Breaking capacity hits 187 kA at 240 V and 121 kA at 415 V — that's the fault current it can safely interrupt without welding contacts or cascading upstream. Rated insulation voltage is 800 V, so it's comfortable in 480 V / 600 V panels.
What the ratings mean for fit
Three poles, no undervoltage release, no shunt trip, no ground-fault monitoring — this is a straight thermal-magnetic breaker for basic feeder or branch protection. The 25 A continuous rating holds flat through 50 °C; above that it derates to 24 A at 55 °C and 22.5 A at 70 °C. If your panel ambient runs hot, that derate curve matters. The TM240 release is fixed, not adjustable — you get one trip curve, no dials. IP40 on the front means it's protected against tools and wires >1 mm, but not against water spray; keep it inside a sheet-metal enclosure.
Panel fit and auxiliaries
It ships with two HQ auxiliary switches (form C, I assume) for status feedback to a PLC or indicator lamp. No communication module, no phase-failure detection — it's a standalone breaker. Physical dimensions: 70 mm deep, 76.2 mm wide, 130 mm tall. That width is a standard three-pole MCCB footprint for this class; it'll land on a DIN rail or panel-mount baseplate without surprises. Operating range is -25 °C to 70 °C, storage from -40 °C to 80 °C.