What it is and what it does
The Siemens 3VA1125-6GE46-0AA0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in distribution panels. Four poles, 25 A continuous at 40 °C, with a TM220 thermal-magnetic trip unit — so the thermal element handles overloads and the magnetic element clears short-circuits without external control wiring. Interrupting capacity is the headline here: 220 kA at 240 V AC, 154 kA at 415 V, 121 kA at 440 V, and 17 kA at 500 V and 690 V. That 220 kA figure at 240 V means it can be placed on the secondary of a large transformer or near a high-fault utility service without worrying about the breaker failing to clear — the SCCR headroom is substantial. Rated insulation voltage is 800 V, operating voltage 690 V AC. The 4-pole design with 100% N-conductor protection means the neutral pole is fully rated, not just a switched neutral — important for 3-phase + N panels where you need the neutral protected against overload.
Thermal derating and panel fit
The 25 A rating holds flat from 40 °C through 50 °C, then drops to 24 A at 55–60 °C, and 23 A at 65–70 °C. If you are packing this into a warm enclosure — say a non-ventilated panel near a furnace line — that derating curve is the one that governs your actual ampacity, not the 25 A label. Footprint: 101.6 mm wide, 130 mm tall, 70 mm deep. That 101.6 mm is a standard 4-inch width, so it occupies four 25 mm DIN-module spaces on the rail. The 70 mm depth means it clears a 100 mm deep enclosure backplate without the line-side lugs hitting the cover — I have seen 80 mm deep breakers that force a deeper can. Front face is IP40 — fine for a clean indoor panel, not for washdown. No trip indicator, no undervoltage release, no communication module on this variant. It is a straight thermal-magnetic breaker: wire it in, it trips, you reset it manually.