What the D-curve and 20 A rating mean on site
It's a current-production part (lifecycle stage: current), so no last-time-buy scramble; you can specify it into a new panel or drop it into a retrofit without worrying about obsolescence. At 400 V AC, that 25 kA SCCR gives you headroom for high-fault installations without cascading upstream. For DC circuits, it's rated 15 kA at 72 V DC per IEC 60947-2, and 5 kA under UL 1077 / CSA C22.2 No. 235 for North American acceptance.
At 18 mm wide (1 width unit), it's a standard single-module MCB that snaps onto DIN rail without needing extra side space. The touch-protected terminals (IP20 with connected conductors) keep fingers away from live parts inside the enclosure — fine for a panel that gets opened for troubleshooting. Humidity derating is specified: max 95% RH up to 55 °C, dropping to 55% at 70 °C and 35% at 75 °C. In a non-climate-controlled panel near a washdown zone, that's the limit to watch — keep the cabinet ventilated if ambient humidity sits high alongside elevated temps.
The design is the 5SY7 series, a compact single-pole MCB family that shares the same footprint and terminal layout across the D-curve range.