The Siemens 3RT2936-1CF00 is a SIRIUS RC surge suppressor sized for S2 frame contactors — the 3RT2.3 series. It clips directly onto the contactor coil terminals, so no additional wiring or DIN-rail space is needed. The RC element snubs the voltage spike when the coil de-energizes, which is what kills nearby electronics and welds auxiliary contacts over time.
Rated 400... 600 V AC at both 50 Hz and 60 Hz — this covers the common control-voltage range for European and North American panels running on 400 V or 480 V line-to-line. The AC-only coil voltage means it is not for DC-operated contactors; if your coil is 24 V DC, this suppressor will not clamp the right waveform. The 15 mm depth, 30 mm width, and 30 mm height (–) are the physical envelope once clipped onto the contactor. Because it mounts on the coil terminals, it adds zero footprint to the panel — the contactor itself already occupies that DIN-rail slot. Clip-on fastening with any mounting position means the installer presses it onto the contactor's coil terminals — no screws, no tool. The S2 frame size is the key compatibility gate: this suppressor fits 3RT2.3 contactors only. It will not mechanically mate with S00, S0, S3, or S6 frames.