What it is and what the ratings mean
The Siemens 3RU2136-4DD0 is a SIRIUS Size S2 thermal overload relay, Class 10 trip characteristic. Class 10 means it must trip within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a locked-rotor start without nuisance tripping on normal acceleration. The thermal bimetallic element tracks motor heating, so it responds to actual RMS current, not just peak. It mounts directly to a contactor via the fastening method (contactor mounting), saving panel space and wiring. The integrated auxiliary switch provides a separate signal path for the tripped state — the Note for message "Tripped" on the device face confirms the relay has operated.
Motor power coverage across common voltages
This relay covers motor loads up to 11 kW at 400 V, 15 kW at 500 V, and 22 kW at 690 V in AC-3e duty. The auxiliary contact ratings span control voltages: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. That means the N.O. auxiliary can switch a PLC input or a contactor coil at the same voltage as the motor circuit without an interposing relay — a common panel simplification.
Mounting and wiring
Mounts in any position directly onto the contactor — no separate DIN-rail footprint needed. Main circuit connections use screw-type terminals accepting 2× (0.5 to 2.5 mm²) solid or stranded conductors. The screwdriver shaft diameter is 5 to 6 mm, Pozidriv PZ2 tip. Main contact screws are M6. Depth is 105 mm, width 55 mm, height 90 mm. The temperature compensation range is -40 to +60 °C, meaning the trip curve stays accurate across that ambient span without manual adjustment.