The ABB XT3NU3150AFF00NXXX is a 3-pole molded case circuit breaker (MCCB) from the XT3N series, fitted with a TMF 150-1500 thermal-magnetic fixed trip unit on a 225 A frame. The description on record reads XT3N 225 TMF 150-1500 3P F F UL/CSA — the F F stands for fixed front terminals and fixed instantaneous pickup, meaning the breaker ships with a factory-set magnetic trip threshold and non-interchangeable thermal element. The UL/CSA suffix confirms it carries the North American safety certifications needed for panelboard and switchboard installations in the US and Canada.
The 225 A frame size and TMF 150-1500 trip unit mean this breaker is sized for branch-circuit protection on loads drawing between 150 A and 1500 A of fault current — typical for motor control centers, feeder circuits in industrial panels, or large HVAC equipment. The fixed thermal-magnetic trip gives a defined time-current curve with no field-adjustable electronic settings, which simplifies coordination studies: the engineer knows exactly the long-time and instantaneous pickup points from the TMF rating. The 3-pole fixed configuration (no plug-in base, no rotary handle) is the standard panel-mount format for a DIN-rail or direct-screw mounting in an enclosed switchboard.
This breaker is used in commercial and industrial power distribution — lighting panels, motor control centers, feeder tap boxes, and switchboards. The UL/CSA listing fits North American code-compliant installations.