What this MCCB is and what it does
The Siemens 3VA1125-5EF36-0CA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It's a 3-pole unit rated 25 A at 40 °C with a TM240 thermal-magnetic overcurrent release, and it carries an undervoltage release (UVR) built in — that's the -5EF36 suffix telling you the UVR is factory-fitted, not a field-add-on. Breaking capacity is the headline number here: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V. That 187 kA at 240 V means this breaker can safely interrupt a fault current up to that level without welding contacts or cascading upstream — it's sized for high-fault industrial panels, not light commercial. Rated insulation voltage is 800 V, so it's suitable for 690 V line-to-line systems with margin. Power loss runs 11 W maximum at rated load — that's the heat you need to account for in a closed panel.
Current derating — the real-world number
The 25 A rating holds flat from 40 °C through 50 °C. At 55 °C it derates to 24 A, at 60 °C still 24 A, at 65 °C drops to 23 A, and at 70 °C stays at 23 A. That's a shallow derating curve — you lose only 2 A over a 30 °C rise — so if your panel ambient runs warm, this breaker still carries most of its nameplate. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit governs handling and warehousing, not running conditions.
Panel fit and mounting
Dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — that's roughly 5.12 by 3 by 2.76 inches. It mounts on a DIN rail or can be screw-fixed to a backplate; the 3-pole width is standard for a 25 A MCCB frame, so it drops into the same panel cutout as other SENTRON 3VA breakers of this frame size. No communication function, no ground-fault monitoring, no voltage trigger or trip indicator on this variant. It's a straight line-protection breaker with undervoltage release — keep it simple for the BOM.