The Siemens SIRIUS 3RH1122-1BB40-0TK0 is an auxiliary contactor in the S00 frame size, carrying 2 normally-open instantaneous contacts and a 24 V DC coil. It's the signal-switching half of a contactor pair — the part that tells the PLC or safety relay that the main power contactor has picked up, or that routes control voltage to the next stage in a motor starter stack.
What the ratings mean for fit
The AC-12 rated current of 10 A covers resistive and solid-state loads typical of control circuits — PLC digital outputs, relay coils, indicator lamps. Don't confuse this with AC-3 motor switching; these contacts are for pilot duty, not power. The 24 V DC coil pulls 3.2 W on pickup and holds at 3.2 W, so the control transformer or DC supply needs to deliver that continuously — no coil economizer on this variant. The 6 kV surge voltage resistance (rated impulse withstand) means this contactor can live on a 400 V panel without external surge suppression for most industrial environments, provided the panel's own SPDs are in place. Pollution degree 3 confirms it's rated for conductive environments — the typical non-cleaned panel.
Mounting and integration
Snap-on mounting to 35 mm DIN rail, or screw-mount through the base — your choice. The 45 mm width (3 TE on a standard DIN rail) and 72 mm depth mean it fits alongside a S00 contactor in a compact starter arrangement. Mounting position is flexible: vertical surface with ±180° rotation, plus ±22.5° tilt forward/backward, so it adapts to tight enclosures without derating. Terminals accept 2x 0.5–1.5 mm², 2x 0.75–2.5 mm², or 2x 4 mm² solid — the dual-wire capacity is useful for daisy-chaining control voltage across multiple auxiliaries without extra terminal blocks. IP20 on the front means it's protected against finger contact but not washdown; keep it inside the enclosure.