The ABB XT3NU4225AFF000XXX is a molded case circuit breaker from the XT3N 225 series, carrying a 225 A frame and fitted with a TMF 225-2250 thermal-magnetic trip unit. The 4-pole configuration with fixed thermal and fixed magnetic settings makes it a straightforward choice for distribution panels where you need UL/CSA-listed overcurrent protection and don't plan to swap trip units in the field. The TMF trip provides inverse-time thermal protection for overloads and instantaneous magnetic protection for short circuits, covering the range from 225 A up to 2250 A magnetic pickup.
The 225 A frame and TMF 225-2250 trip unit mean this breaker is sized for main feeder or large branch protection in a 480 V distribution panel. The fixed thermal setting at 225 A matches continuous load current up to that value; the magnetic pickup adjustable from 225 A to 2250 A lets you coordinate with downstream breakers and avoid nuisance tripping on motor inrush. The 4-pole version handles three-phase plus neutral or two-pole loads on a 3-phase 4-wire system. UL/CSA listing covers North American installations; the breaker mounts in a standard ABB XT3 panelboard or can be installed in an enclosed MCC bucket.