The Siemens SIRIUS 3RT2926-1MR00 is a surge suppressor — a diode combination with an integrated LED indicator — designed specifically for 24 V DC control circuits on 3RT2.2 contactors. It clips onto the contactor coil terminals, suppressing the inductive flyback voltage that occurs when the DC coil de-energizes. Without it, that voltage spike can weld relay contacts or damage the PLC output driving the coil. The LED gives a quick visual on coil energization, which helps during panel commissioning or fault-finding. This is the S0-size variant, meaning it mates with the S0 frame contactors in the 3RT2.2 family. The clip-on fastening method means it snaps directly onto the contactor without tools — no extra wiring or DIN-rail space needed. It occupies zero additional panel width because it rides on the contactor itself. The mounting position is unrestricted, so it works in horizontal, vertical, or inverted orientations.
Depth is 12 mm, width 30 mm, height 19 mm. These are the suppressor's own dimensions, not the contactor's. Because it clips onto the contactor face, the depth adds to the contactor's front-to-back panel projection. If your enclosure depth is tight — say a shallow gland plate or a door-mounted operator station — that 12 mm extra matters. The 30 mm width is narrower than a standard DIN-rail terminal block, so it won't overhang the contactor body.
Environmental limits
The operating limit is what matters in the panel: at 60 °C ambient, the diode junction still suppresses the coil spike reliably. No derating curve is published for this accessory, but staying within the contactor's own operating range is standard practice.