125 A MCCB with 187 kA interrupting capacity — the selectivity anchor for high-fault panels
The Siemens SENTRON 3VA1112-5GF42-0AA0 is a 4-pole molded case circuit breaker rated 125 A continuous, with a TM240 thermal-magnetic release. Its interrupting capacity hits 187 kA at 240 V AC — that is the figure that governs selectivity coordination in a main feeder panel. At 415 V it still clears 121 kA, and at 440 V it holds 75.6 kA. For a 125 A frame, those numbers mean this breaker can sit upstream of multiple branch feeders without needing a current-limiting fuse ahead of it, as long as the available fault current at its terminals stays under those ratings. The 4-pole configuration covers three-phase plus neutral, with 100 % N-conductor protection.
Thermal derating and panel integration
The breaker holds its full 125 A rating up to 50 °C ambient. Above that it derates linearly: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If the panel ambient runs hot — say, a non-ventilated enclosure near a furnace line — the 70 °C figure is the one to size against. The front face carries IP40 protection, so it tolerates tool contact and dust ingress typical of a closed panel but not washdown. Dimensions are 101.6 mm wide by 130 mm tall by 70 mm deep; the 4-pole width matches the standard 4-module MCCB footprint on a DIN rail or bolted bus. Maximum power loss is 28.1 W — relevant for enclosure thermal calculations when grouping several breakers.
Approvals and compliance documentation
As a SENTRON series MCCB, the 3VA1112-5GF42-0AA0 carries IEC 60947-2 certification for molded case circuit breakers. The rated insulation voltage is 800 V, and the maximum operational DC voltage is 600 V. The manufacturer provides RoHS and REACH declarations through its standard documentation portal. For UL/CSA listings, verify the specific file number against the Siemens 3VA UL mark database — the IEC-rated variant may differ from a UL 489-listed version. The reference code per IEC 81346-2 is Q (switching device).