What this MCCB is and what it does
The Siemens 3VA2125-6HL42-0AA0 is a SENTRON molded case circuit breaker (MCCB) configured for line protection — meaning it guards feeders and distribution branches against overcurrent and short-circuit faults, not motor loads. It carries a rated continuous current Iu of 25 A across its full ambient temperature range from 40 °C to 70 °C with no derating, which simplifies panel sizing in warm enclosures. The 4-pole design switches all three phases plus neutral, with the N-conductor protection adjustable to OFF or 100% of the phase rating. The ETU320 electronic trip unit gives you adjustable time-current curves — the long-time delay tr is settable between 0.5 and 17 seconds — so you can coordinate selectivity downstream without oversizing the main breaker. Rated insulation voltage Ui is 800 V, and the front face carries IP40 protection, adequate for dry indoor panel installations.
Breaking capacity — what the numbers mean for your fault duty
This MCCB delivers 242 kA at 240 V, 187 kA at 415 V and at 440 V, 121 kA at 500 V, and 3.8 kA at 690 V. Those are the ultimate short-circuit breaking capacities (Icu) at each voltage level — the fault current the breaker can safely interrupt once. At 415 V, 187 kA covers nearly any industrial transformer secondary or high-fault panel bus; the drop to 3.8 kA at 690 V means it's not intended for 690 V main feeders, but for 400/415 V distribution it has headroom to spare.
Panel fit and dimensions
The breaker measures 140 mm wide, 181 mm high, and 86 mm deep — a standard SENTRON 3VA2 frame footprint that drops into existing panel cutouts and busbar systems designed for the series. The 4-pole width (140 mm) is wider than a 3-pole unit; verify your busbar spacing and enclosure depth before committing the BOM. An optional motor drive can be added as a product extension for remote tripping or re-closing schemes.