What the ratings mean for fit
The ABB XT1NU3030AFF000XXX is a Tmax XT1 molded case circuit breaker rated 30 A continuous, 3-pole, for 480 VAC systems with a 18 kA interrupting capacity at that voltage. That 18 kA SCCR means it can safely clear a bolted fault up to that level without upstream devices needing to coordinate — a critical number for panel SCCR labeling under UL 508A. The panel-mount footprint (not DIN-rail) means it bolts into a cutout or sub-panel, common in industrial distribution boards and OEM control cabinets.