What this SIRIUS size S0 contactor carries
The Siemens 3RT1326-3XF48-0LA3 is a SIRIUS power contactor in the size S0 frame, rated for 11 kW at AC-2 duty at 400 V. It carries four normally-open main contacts and no NC main contacts, so it's built for make-only switching — think resistive or lightly inductive loads where you need to close multiple poles simultaneously. The 110 V DC coil includes a built-in varistor surge suppressor, which saves you an external snubber on the coil circuit. Screw-type terminals on the main circuit accept up to 2x 10 mm² stranded or 1x 12 AWG, and the control circuit takes 2x (0.25... 2.5 mm²) solid.
Integration into a panel — what fits
At 71 mm wide, 119 mm tall, and 101 mm deep, this contactor fits the standard S0 footprint. The IP20 front face means finger-safe above the panel; the terminal area carries IP00, so live parts are exposed below the mounting surface — plan for finger-duct covers or shrouding if the panel is open. Side-by-side mounting is rated for full current without derating, which keeps the rail density up. The varistor is integrated, so no separate surge suppressor module to wire in. For type 2 coordination, the recommended upstream fuse is 35 A gL/gG; for type 1, 63 A gL/gG. That's your selectivity headroom when sizing the feeder breaker.