What this MCCB delivers — and what it doesn't
The Siemens SENTRON 3VA1225-5GF42-0KC0 is a 4-pole molded case circuit breaker rated for 250 A continuous current (Iu) at up to 50 °C, with a TM240 thermal-magnetic overcurrent release. Its short-circuit breaking capacity reaches 187 kA at 240 V and 121 kA at 415 V — numbers that tell you it's sized for high-fault infrastructure, not light branch protection. The 800 V rated insulation voltage (Ui) confirms it can sit on 690 V line-to-line systems without derating the insulation path. This is a line-protection device — no ground-fault monitoring, no undervoltage release, no communication module, and no phase-failure detection built in. What it does carry is a shunt trip (STL) for remote opening and two auxiliary switches (HQ) for status feedback. If your panel needs a simple, high-interrupt MCCB with a clean auxiliary contact set, this fits. If you need integrated ground-fault or undervoltage protection, you'll add external modules or look at a different variant.
Thermal derating curve — the real continuous current
The 250 A rating holds flat from 40 °C through 50 °C ambient. Above that, the TM240 release begins to thermally derate: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If your panel ambient runs at 60 °C, you're limited to 236.5 A continuous — not 250 A. Plan the load accordingly, especially in a sealed enclosure with other heat sources.
Mounting and integration
The breaker measures 140 mm wide, 158 mm high, and 70 mm deep — a 4-pole frame that fits standard SENTRON mounting plates and panel cutouts. IP40 on the front means it's protected against tools and solid objects larger than 1 mm, but not against water ingress; keep it inside a sealed enclosure in wet environments. The 100% N-conductor protection means the neutral pole is fully rated and switched — no derating on the neutral path.