What this breaker is and what the ratings mean for fit
The Siemens 3VA1125-5GF42-0AA0-ZD00 is a 4-pole molded case circuit breaker on the IEC 160 A frame, rated for 55 kA breaking capacity at 415 V AC — that is the Icu (ultimate breaking capacity) under class M, meaning it can safely interrupt a fault up to that level once and still carry rated current afterward. For a 25 A line protection breaker, that is serious fault-current headroom; it stays coordinated with downstream devices without cascading upstream. Overload protection is adjustable: Ir from 18 A to 25 A via the TM240 thermal-magnetic trip unit. Short-circuit pickup Ii spans 6.4 to 12.8 times In, so at the 25 A setting that is 160 to 320 A magnetic trip. The 100% N-conductor protection means the neutral pole is fully rated — no derating needed for unbalanced loads or harmonic-rich circuits. This variant includes a nut keeper kit and is configured for a DC Power OEM in China — the ZD00 suffix flags a customer-specific build. The frame is the standard 3VA1 160 A platform, so it mounts in the same panel cutouts and bus-bar arrangements as other 3VA1 breakers.