SIRIUS 3RU2136-1HB0 — Thermal Overload Relay, Size S2, Class 10
The Siemens 3RU2136-1HB0 is a SIRIUS thermal overload relay, Size S2, designed for motor protection with Trip Class 10 tripping characteristic. It mounts directly onto a contactor and provides bimetallic thermal overload protection for three-phase motors up to 690 V rated voltage. Class 10 means the relay trips within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during locked-rotor conditions without nuisance tripping on normal starts. The integrated auxiliary switch provides status signalling: the 'Tripped' message contact changes state when the relay has operated, giving the PLC or HMI a direct fault indication without needing an external limit switch.
Auxiliary Contact Ratings — What They Mean for Your Control Circuit
The integrated auxiliary switch is rated for multiple control voltages: 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. These are the maximum continuous currents the auxiliary contacts can switch at each voltage level — use the 690 V row when the control circuit is line-fed rather than transformer-isolated. At lower control voltages (24 V, 60 V, 110 V, 125 V, 220 V) the ratings are 2 A, 0.3 A, 0.22 A, 0.22 A, and 0.11 A respectively — the 60 V and 125 V entries cover non-standard control supplies sometimes found in marine or legacy installations.
Motor Power Ratings — Sizing to the Load
At 400 V rated value the relay handles 3 kW; at 500 V it handles 4 kW; at 690 V it handles 5.5 kW. These correspond to the motor full-load current the relay can protect when set correctly. The 480 V and 600 V entries (8 A each) cover North American 60 Hz installations where the relay is applied at those voltages.
Mounting & Integration — What Fits Where
Fastening method is contactor mounting — the relay clips directly onto the matching SIRIUS contactor, no DIN rail required. Mounting position is any orientation, which simplifies panel layout. Dimensions: 55 mm wide, 90 mm high, 105 mm deep. Main circuit terminals accept screw-type connections: 2× (0.5…1.5 mm²) or 2× (0.75…2.5 mm²) solid or stranded. Use a Pozidriv PZ2 screwdriver with 5–6 mm shaft diameter.
Environmental & Compliance
Operating temperature range is -40 to +70 °C; storage and transport range is -55 to +80 °C. Temperature compensation is active from -40 to +60 °C, meaning the relay's trip characteristic stays accurate across that span without manual adjustment. Substance prohibitance date of 09/08/2017 aligns with RoHS and REACH compliance documentation available from Siemens for this part.