Rated for the panel, not the bench
The Siemens 5SY7420-6 is a 4-pole SENTRON miniature circuit breaker rated 20 A with a B tripping characteristic. It clears faults at 15 kA per EN 60898 and 25 kA per IEC 60947-2 at 400 V AC — that IEC rating means it's certified for industrial panel applications where fault currents can exceed the residential standard. If you're feeding a 400 V three-phase sub-distribution board or a machine control cabinet, this is the interrupting rating that matters. The B curve trips at 3–5× In, so it's sized for resistive and general-purpose loads — lighting banks, control transformers, small heating elements — not motor inrush. For a 20 A circuit feeding a 4 kW resistive load on a 400 V line, this holds without nuisance tripping. DC side: rated 72 V maximum, so it can protect a 48 VDC control bus but not a 110 VDC battery bank. Mounts on DIN rail via the quick-assembly system (4 width units at 18 mm each = 72 mm wide). IP20 with conductors connected — fine inside a closed panel; not for wet or outdoor locations. Touch protection is built in, which matters for live-busbar work during commissioning.
Sourcing and lifecycle
Compliance documentation is standard for the SENTRON line: the breaker carries approvals per EN 60898 and IEC 60947-2, plus UL 1077 and CSA C22.2 No.235 recognition at 5 kA (AC). Halogen-free and silicon-free construction, which simplifies disposal and outgassing requirements in clean-room or sealed-panel environments.
Deployment context
Designed for mechanical engineering and industrial panel builds. The 4-pole form factor handles three-phase plus neutral (neutral conductor switching is not built in — this is a 4-pole breaker that switches all four poles, not a 3P+N with a solid neutral). Installation depth is 70 mm, so it fits standard 80 mm deep enclosures with room for wiring behind the DIN rail. Ambient temperature range -40 °C to 75 °C, with derating above 55 °C per the humidity curve (95% RH at 55 °C, 55% at 70 °C, 35% at 75 °C).