The Siemens 3RT2036-1KB40 is a SIRIUS coupling contactor in the S2 frame size — a compact, screw-terminal device rated for switching auxiliary and control circuits, not main motor power. It carries 18 normally-open and 1 normally-closed main contact configuration, so it's built for interposing or signal-level coupling between a PLC output and a larger contactor coil or indicator load. The 24 VDC coil holds at 0.8× rated voltage and picks up reliably at 1.2× rated, with dropout below approximately 19.2 V — standard SIRIUS coil behaviour that matches the rest of the 3RT2 family. Mounting is screw-and-snap-on to 35 mm DIN rail per DIN EN 60715, with the mounting position allowing ±180° rotation on a vertical surface and ±22.5° tilt forward/backward — flexible for tight enclosures. Dimensions are 114 mm high, 55 mm wide, 130 mm deep, placing it in the standard S2 footprint that shares panel cutouts with the 3RT2036-1AC20-ZX95 and other S2-frame siblings.
The auxiliary contact switching capacity is rated per voltage: 10 A at 24 V DC, 2 A at 48 V and 60 V DC, 1 A at 110 V DC, 0.9 A at 125 V DC, 0.3 A at 220 V DC, and 3 A at 400 V AC. This means the contactor can handle typical PLC-level loads (24 VDC relays, indicator lamps) at the full 10 A, but derates significantly at higher DC voltages — a 220 VDC solenoid would be limited to 0.3 A. The AC-1 maximum operating frequency is 1,000 cycles per hour, dropping to 250 cycles per hour at AC-4 (plugging/reversing duty). Coil inrush peaks at 2.6 A, with arcing time of 10 to 20 ms and DC operating time of 30 to 55 ms — fast enough for most interposing applications but not for high-speed synchronous switching. The screw-type terminals accept 2×(0.5 to 1.5 mm²) or 2×(0.75 to 2.5 mm²) solid or stranded wire, which covers standard control wiring up to 14 AWG.
Panel integration — clearances and environment
Clearance requirements: 10 mm upward and forward, 10 mm downward, 6 mm at the side — tight enough for dense DIN-rail layouts. The part includes an auxiliary switch block (factory-fitted) and carries the SIRIUS brand designation typical of Siemens' modular contactor family.