What this contactor is and where it lands
The Siemens SIRIUS 3RT1055-6SF36-3PA0 is a size S6 power contactor rated for motor and resistive loads, with a 96-127 VAC coil and screw-type coil terminals. It mounts via screw fixing on a vertical surface and can be rotated ±90° or tilted ±22.5° front-to-back, which gives flexibility in a crowded panel layout. At 120 mm wide and 172 mm tall, it takes up a standard S6 footprint on the gland plate. The 170 mm depth means you need that clearance behind the door for the arc chamber and main pole connections.
Key ratings and what they mean for the panel
The coil pulls in at 0.8 of rated voltage and holds with a 1.1 full-scale factor, so on a 110 VAC control bus it picks up cleanly at 88 V and stays sealed through 121 V. Operating temperature range is -25 to +60 °C, which covers most indoor industrial enclosures without derating. The MTBF is listed at 75 a — that is a mean time between failures of 75 years under stated conditions, a reliability figure that supports long-life BOM planning. For load wiring, the main poles accept stranded cable from 25 to 120 mm², sized for the full current capability of the S6 frame. Auxiliary contacts are present, so you can wire status feedback without an add-on block.
Mounting and wiring notes
Screw fixing on a vertical surface is standard. The coil terminals are screw-type, which a panel wireman can torque to a known value — no spring clips to second-guess. Minimum clearances around the contactor: 10 mm upwards, 10 mm downwards, 20 mm forwards, and 10 mm at the side. If you are packing multiple S6 contactors side by side, that 10 mm side gap is the minimum for heat dissipation and arc clearance. The main power connections accept stranded 25-120 mm²; auxiliary wiring takes 0.5-1.5 mm² solid or stranded, with a maximum of 4 mm² on the larger terminals. Wire it with ferrules for a clean termination.