Rated current and breaking capacity — what they mean for panel fit
At 35 °C the breaker carries its full 20 A rating; at 40 °C it derates to 19.04 A, at 50 °C to 18.04 A, and at 60 °C to 16.96 A — the full derating table is listed for panel builders calculating fill factor in a warm enclosure. Operating ambient range is -40 °C to 75 °C, with humidity limits of 95% up to 55 °C, tapering to 35% at 75 °C — this covers most indoor industrial and outdoor cabinet installations.
The 5SY4320-5 is certified to IEC / EN 60898-1 and IEC / EN 60947-2, plus UL1077 — the UL1077 listing means it is accepted as a supplementary protector in North American panels, not a branch-circuit rated device under UL 489.
Snap-on DIN rail mount, 3 modular width units (54 mm wide), 76 mm depth, 90 mm height — fits standard 35 mm DIN rail enclosures; the quick-assembly system allows ganging without tools.