What it is and what it does
The Siemens 3RU2136-4GD0 is a SIRIUS thermal overload relay, size S2, designed to protect motors against overload and phase failure. It is a Class 10 device, meaning it will trip within 10 seconds at 7.2× the set current — the standard trip class for standard-start induction motors, not for high-inertia loads that need a slower Class 20 or 30. Rated for a maximum of 690 V, it carries motor power ratings of 22 kW at 400 V, 30 kW at 500 V, and 37 kW at 690 V. At 480 V and 600 V it is rated for 45 A. The auxiliary contact block is integrated, with switching capacities of 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V. The overload release is thermal, with temperature compensation active from -40 to +60 °C. The relay mounts directly onto a contactor (contactor mounting), in any position. The main circuit terminals are screw-type, accepting 2× (0.5 to 2.5 mm²) solid or stranded wire, requiring a Pozidriv PZ2 screwdriver tip.
Sourcing and lifecycle
RoHS compliance is documented with a substance prohibitance date of October 15, 2014, covering the standard EU RoHS scope.
Integration notes
The relay measures 55 mm wide, 90 mm high, and 105 mm deep. It mounts directly onto a contactor — no DIN rail required, but the contactor itself is typically DIN-rail mounted in the panel. The M6 main contact screws and the 5–6 mm diameter screwdriver shaft specification are standard for panel wiring. Power dissipation per pole is 5.2 W, so for a three-phase motor the total heat load in the enclosure is about 15.6 W from the relay alone. Account for this when sizing panel ventilation. The note on the component line reads "for message 'Tripped'", which is the status indication the relay sends to a PLC or HMI when it has operated.