The ABB XT4VU3040EFF000XXX is a 3-pole molded case switch from the XT4V 250 EKI series, rated for 20 A continuous current. The 20 A rating means it handles motor loads or resistive circuits up to that ampacity without nuisance tripping — sized for a branch circuit feeding a moderate pump, conveyor, or lighting panel. Wall-mounting keeps it out of the DIN-rail density game; you bolt it to the backplate or enclosure side, freeing rail space for smaller breakers and contactors.
The 4 W power dissipation listed for this switch is the heat it sheds under rated load — relevant for enclosure thermal budgeting. In a sealed steel box with other heat sources, that 4 W adds up; account for it when sizing ventilation or a cooling fan. The wall-mount form factor also means the heat sinks into the backplate rather than convecting off a DIN rail, so keep the mounting surface clean and conductive.