What it is and where it fits
The Siemens 3RU1126-1HD1 is a SIRIUS thermal overload relay in the S0 frame size, designed to protect three-phase motor loads against overcurrent and phase failure. It is a stand-alone installation device.
Mounting and clearances
Mounts on a vertical surface; the relay can be rotated ±135° or tilted ±45° front-to-back, so you can orient it to fit the gland plate layout. Zero clearance needed upwards, forwards, backwards, and downwards — only 6 mm at the sides. That makes it a tight fit for crowded DIN-rail enclosures where every millimeter counts. The main circuit uses screw-type terminals (accepts 1x 16–12 AWG or 1x 14–8 AWG); the auxiliary and control circuit uses Cage Clamp terminals (accepts 2x 20–14 AWG). Finely stranded wire with ferrule: 2x 0.5–1.5 mm².
Environmental and compliance
Rated for operation from -20 to +70 °C, storage and transport from -55 to +80 °C, and 100 % relative humidity. IP20 on the front. ATEX approval DMT 98 ATEX G 001. Surge voltage resistance rated at 6 kV, shock resistance 8g for 10 ms. Lifecycle status is current production.
Auxiliary contact ratings
The built-in auxiliary contact is rated across common control voltages: 1 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. That covers most PLC or relay coil loads without an add-on block. Per-pole power dissipation is 2.2 W — factor that into the enclosure thermal budget if you are stacking several relays side by side.