What it is and what it does
The Siemens SENTRON 3VA1125-4EF32-0HC0 is a 3-pole molded case circuit breaker (MCCB) rated for a continuous current Iu of 25 A, with a rated insulation voltage Ui of 800 V. It's the line protection version, meaning its primary job is protecting cable and bus from overloads and short circuits in a distribution panel — not motor protection, not generator protection. The TM240 overcurrent release is a thermal-magnetic unit: the thermal element handles sustained overloads, the magnetic element clears high-current faults fast.
Breaking capacity — what the numbers mean for your panel
This MCCB carries a 121 kA breaking capacity at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V. Those are the maximum fault currents it can safely interrupt at each voltage level without welding contacts or venting plasma. For a 415 V industrial panel, 75.6 kA SCCR gives you headroom above most transformer-fed bus ratings — you're not riding the edge of coordination. At 690 V the 11.9 kA figure is lower, so check your available fault current if this breaker lands on a 690 V bus.
Thermal derating — the real current you get at panel temperature
Rated 25 A continuous at 40 °C, and it holds that rating flat through 50 °C. At 55 °C it derates to 24 A, at 60 °C to 23.5 A, at 65 °C to 23 A, and at 70 °C to 22.5 A. If your panel ambient runs 55 °C or higher — common in sealed enclosures with multiple breakers ganged together — you need to account for that 1–2.5 A drop. The operating temperature range is -25 °C to 70 °C, so it's fine for unheated plant floors in winter.
Built-in accessories — what's on board
Comes with 2 auxiliary switches (HQ type) for status feedback to a PLC or indicator lamp. Also includes a shunt trip (STL) — a voltage-triggered release that lets a remote signal (E-stop, fire alarm, undervoltage relay) trip the breaker electrically. The integrated auxiliary trip is order code 3VA9688-0BL30. No undervoltage release, no communication module, no ground-fault monitoring on this variant — it's a straightforward line-protection MCCB with remote trip capability and auxiliary contacts.
Physical fit and panel integration
Dimensions: 130 mm height, 76.2 mm width, 70 mm depth. That's a standard 3-pole MCCB footprint — mounts on a DIN rail or direct-panel with the appropriate mounting base. The IP40 front protection means it's splash-safe from the front but not sealed; install inside a panel with a door, not in a washdown zone. The 15,000-cycle latching endurance (mechanical) is typical for this class — fine for distribution duty where it operates a few times a year, not for frequent switching.