What this MCCB carries and where it fits
The Siemens SENTRON 3VA1112-4EF32-0CA0 is a 3-pole molded case circuit breaker rated for 125 A continuous current (Iu) with a TM240 thermal-magnetic overcurrent release. It's the line-protection variant — meaning it's built for feeder and distribution duty, not motor-circuit protection with integrated overloads. The TM240 release gives you a fixed thermal pickup and magnetic trip tailored for cable and busbar protection. Breaking capacity is the headline number here: 121 kA at 240 V AC, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V. That's high-interrupting capacity for a 125 A frame — it'll sit comfortably upstream of smaller breakers in a distribution board where fault currents are high. The 690 V figure is worth noting if you're working on 690 V industrial networks; most MCCBs in this class drop off sharply above 480 V. Thermal derating is published across the full operating range: full 125 A up to 50 °C, then 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. If your panel ambient runs hot — say near a furnace line or in a non-climate-controlled enclosure — the 55 °C derate is the one that governs your actual load capacity. The 70 °C ceiling matches the max operating temperature spec.
Integration and mounting
The 3VA1112-4EF32-0CA0 measures 130 mm high, 76.2 mm wide, and 70 mm deep. An undervoltage release (UVR) is fitted as standard — part number 3VA9608-0BB24 for the integrated auxiliary trip. That's a coil that trips the breaker when control voltage drops below a threshold, common in safety circuits where loss of control power must open the main disconnect. No auxiliary contacts are included on this variant; if you need status feedback to a PLC or SCADA, you'll add the auxiliary contact block separately. Mechanical endurance is rated at 15,000 operations.
Lifecycle and sourcing reality
The closest functional sibling is the 3VA1112-5EF32-0CA0, which shares the same 125 A frame, 3-pole count, and TM240 release but carries a different internal accessory configuration.
What the ratings mean for your panel
The 800 V rated insulation voltage (Ui) indicates clearance and creepage designed for 690 V systems with margin. Storage temperature range is -40 °C to 80 °C, wider than the operating range of -25 °C to 70 °C. That storage spec governs warehousing and shipping — not a concern for the installed panel, but relevant if you're staging spares in an unheated warehouse. No communication function, no phase failure detection, no ground fault monitoring on this variant.