What it is and what it does
The Siemens SENTRON 5SY8225-8 is a 2-pole miniature circuit breaker (MCB) with a D tripping characteristic, designed for branch-circuit protection in industrial control panels. It is rated for a breaking capacity of 30 kA at 400 V AC per IEC 60947-2, which means it can safely interrupt fault currents up to that level without upstream coordination failure — critical for high-fault installations like motor control centers or transformer secondaries.
Key ratings and what they mean for fit
The D-curve tolerates high inrush of motor loads, transformers, or welding equipment without nuisance tripping. Mounting is straightforward: the 36 mm width (2 modular units) snaps onto a DIN rail via the quick-assembly system, and it can be installed in any position. The IP20 rating (with connected conductors) is standard for enclosed panel use — not for washdown environments. Depth is 76 mm, installation depth 70 mm, so it sits flush with other SENTRON 5SY series breakers in a multi-unit assembly.
Environmental and compliance profile
Halogen-free and silicon-free construction suits clean-room or semiconductor-adjacent panels. Ambient temperature range is -40 °C to 75 °C. Pollution degree 3 and overvoltage category III mean it is rated for fixed installations in industrial environments with conductive pollution (e.g., dust, condensation). The sealable design allows the installer to lock the toggle position with a padlock — useful for lockout/tagout compliance on a branch circuit.