The Siemens 3RU2136-4QD0 is a SIRIUS thermal overload relay, Size S2, designed for contactor mounting. It provides motor protection with a Trip Class 10 characteristic, meaning it will trip within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a stall or locked-rotor event without nuisance tripping on normal starting transients. Rated for main circuits up to 690 V at 50/60 Hz, it carries motor ratings of 30 kW at 400 V and 55 kW at 690 V. The integrated auxiliary switch provides signal feedback for the tripped state — the "Note for message 'Tripped'" on the nameplate is your confirmation contact.
Ratings and what they mean for fit
The auxiliary contact ratings tell you what control voltage this relay can switch: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. If your PLC output or control relay drives a 24 VDC signal through the tripped contact, you're within the 2 A limit — no interposing relay needed. At 120 VAC, the 3 A rating covers most pilot-duty loads. Temperature compensation spans -40 to +60 °C, so the trip curve stays accurate across the panel's ambient range. The operating temperature range of -40 to +70 °C covers most industrial enclosures; storage and transport tolerance down to -55 °C means it can sit in an unheated warehouse without issue. Screw-type terminals on the main circuit accept 2× (0.5 to 2.5 mm²) solid or stranded conductors, with a Pozidriv PZ2 screwdriver tip. The M6 main contact fastening matches standard contactor busbar connections.
Lifecycle and sourcing reality
Substance prohibitance per the evidence dates to October 15, 2014 — this aligns with the RoHS compliance horizon. No UL, CSA, or IEC certification marks are explicitly listed in the spec record, but the SIRIUS family typically carries IEC 60947-4-1 approval; verify the specific nameplate markings for your jurisdiction.
Integration into the panel
Mounts directly onto the corresponding SIRIUS contactor (no separate DIN-rail footprint — the relay snaps onto the contactor, and the assembly clips onto the DIN rail). Dimensions: 55 mm wide, 90 mm high, 105 mm deep. Any mounting position is permitted, so vertical or horizontal orientation in the enclosure is fine. The thermal design dissipates 5.2 W per pole under load. In a sealed enclosure with multiple relays ganged together, account for this heat in your thermal budget — especially if ambient is near the +70 °C operating ceiling.