What this relay is and what it does
The Siemens 3RU1126-1KD0 is a SIRIUS thermal overload relay, size S0, with CLASS 10 trip characteristics. It mounts directly onto a contactor. The main circuit connects via screw-type terminals, rated for solid conductors 2x (0.5... 2.5 mm²) or AWG 2x (16... 12) / 2x (14... 8). The front face carries IP20 protection.
Electrical ratings and what they mean for your panel
The maximum operating voltage in AC-3 duty is 690 V. Surge voltage resistance is rated at 6 kV. Power dissipation in hot operating state is 6.6 W total, or 2.2 W per pole. Ambient operating range is -20 to +70 °C. Shock resistance is rated at 8g for 10 ms, and the relay can be mounted on a vertical surface with ±135° rotation and ±45° tilt forward/backward — flexible positioning for tight enclosures. Altitude limit is 2 000 m without derating.
Lifecycle and sourcing reality
The ATEX approval (DMT 98 ATEX G 001) means it's certified for use in potentially explosive atmospheres — a common requirement in chemical, oil & gas, and mining applications. The reference code per DIN EN 81346-2 is 'F' (protective device).
Physical fit and integration
Dimensions: 97 mm high, 45 mm wide, 96 mm deep. The S0 size is the smallest frame in the SIRUS overload relay range, designed to pair with S0 contactors. Clearance: 0 mm upwards, forwards, and backwards — it sits flush against the contactor face. Side clearance is 6 mm for heat dissipation between units. The relay has no auxiliary contacts built in — 0 auxiliary contacts for the main current circuit. If you need signal feedback (trip indication or remote reset), you'll add a separate auxiliary contact block that clips onto the relay.