What the D-curve and breaking capacities mean for your panel
Under UL 1077 the same part carries a 5 kA interrupting rating, which is the number a panel builder in a North American spec needs for the SCCR label. For DC circuits it's rated 15 kA at 60 V, covering battery-backed control buses and solar combiner boxes.
The 5SY8440-8 occupies 4 modular width units (72 mm) on a standard DIN rail, with a depth of 76 mm and height of 90 mm — the 70 mm installation depth leaves clearance behind a standard 120 mm deep enclosure gland plate.
Environmental limits and derating
Ambient temperature range spans -40 °C to 75 °C, but the breaker's thermal-magnetic trip curve is influenced by surrounding temperature: relative humidity must be derated above 55 °C — max 95% RH up to 55 °C, then 55% RH up to 70 °C, and 35% RH up to the 75 °C ceiling. Vibration resistance per IEC 60068-2-6 is ±1 mm at 5 to 25 Hz and 50 m/s² at 25 to 150 Hz, which covers typical industrial panel vibration from nearby motors and conveyors.