What this MCCB is and where it fits
The Siemens 3VA1125-6GE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated 25 A continuous, 4-pole, with a TM220 thermal-magnetic release — meaning the thermal element handles overloads and the magnetic element handles short-circuits, no electronic trip unit. It's designed for line protection (feeders, distribution panels), not motor or generator protection. The 220 kA breaking capacity at 240 V is the headline number, but the real-world value is the 154 kA at 415 V and 121 kA at 440 V — that's the range where most industrial 3-phase distribution sits, and it gives you serious fault-current headroom without stepping up to a larger frame.
Breaking capacity and selectivity — the numbers that matter
This breaker's interrupting rating drops off steeply above 500 V: 17 kA at 500 V and the same 17 kA at 690 V. That's not a typo — the TM220 release's arc extinction is optimized for the 240–440 V band. If your system runs at 480/277 V or 600 V, the 17 kA rating still covers most downstream panelboard faults, but you'll want to verify the available fault current at that voltage before committing the BOM line. The temperature derating is minimal up to 50 °C (still 25 A), then drops to 24 A at 55–60 °C and 23 A at 65–70 °C — so in a warm enclosure you lose about 8% capacity, not the 15–20% some frames show.
Panel fit and mounting
Dimensions: 70 mm deep, 101.6 mm wide, 130 mm tall. That's a 4-inch wide footprint — standard for a 4-pole MCCB in this class. It mounts on a DIN rail or can be screw-mounted via the base. The IP40 front protection means it's fine in a closed panel; no washdown rating. No undervoltage release, no communication function, no ground-fault monitoring — this is a straight thermal-magnetic breaker, no accessories built in. You add those externally if needed.