The Siemens 3RU2136-4RD1 is a SIRIUS thermal overload relay, size S2, with a Class 10A trip curve. It protects motors against overload and phase failure, rated for main circuits up to 690 V. The thermal bimetal release is temperature-compensated from -40 to +60 °C, so the trip point stays stable across a typical panel ambient range.
What the ratings mean for fit
Class 10A means the relay trips within 10 seconds at 7.2× the current setting — that's the standard for standard-duty motor starting (pumps, fans, compressors) where the start transient is short. The 690 V rated value covers 400 V and 480 V systems with headroom; the power ratings at 400 V (37 kW) and 500 V (55 kW) give a quick sizing reference for common line voltages. The auxiliary switch is integrated, so no separate add-on block is needed for the trip signal. The note "for message 'Tripped'" on the relay indicates that the auxiliary contact position changes when the overload trips — that's the signal you wire back to the PLC or annunciator.
Panel integration and wiring
The relay mounts in any position (stand-alone installation) and accepts screw-type terminals on the main circuit. The main contact terminals take M6 screws; the auxiliary circuit terminals accept 2× (0.5 to 2.5 mm²) solid or stranded wire. At 55 mm wide and 117 mm deep, it fits a standard DIN-rail enclosure with room for adjacent contactors or busbars.