40 A at 400 V — the real-world switching limit
The 5TT5842-2 is a SENTRON insta contactor rated for 40 A operational current at 400 V AC. That 40 A figure is the AC-1 resistive load rating — the current you can count on for heater banks, lighting panels, and similar steady loads where inrush isn't a factor. The 24 V AC coil means this is a control-voltage part, not a 230 V coil variant; make sure your control transformer and PLC output card are rated for the coil draw before wiring it in.
Contact configuration and panel fit
Two normally-open and two normally-closed contacts give you flexibility: you can break both poles of a single-phase load, or use one NO for the load and the other NO for a pilot light, with the NC contacts feeding back status to the PLC. The 3 MW modular width means it occupies three 18 mm DIN-rail slots — a standard footprint for a 40 A contactor in a distribution board. Dimensions are 90 mm high, 54 mm wide, and 71 mm deep, so it fits behind a standard 100 mm deep enclosure door. The installation note calls for spacers to ensure heat dissipation — don't pack it tight against other heat-generating devices without that air gap, or the thermal rating derates faster than you expect.