The Siemens 3RU1116-1JB1 is a SIRIUS thermal overload relay in size S00, designed to protect motors against overcurrent and phase failure by monitoring the current draw and tripping a contactor when the thermal load exceeds the CLASS 10 curve — meaning it will trip within 10 seconds at 7.2× the set current, which is the standard for standard-duty induction motors driving pumps, fans, and conveyors.
The CLASS 10 trip class means this relay is sized for motors that accelerate quickly — it allows a brief inrush without nuisance tripping but clears fast enough to protect the motor winding during a stall. If your motor has a long acceleration time (high-inertia loads like centrifuges), you would need a CLASS 20 or CLASS 30 relay instead. That is the heat you need to vent inside the enclosure — in a dense panel with multiple relays side by side, derating or spacing may be needed to keep the internal ambient below the -20 to +70 °C operating range. Surge voltage resistance is rated at 6 kV, which aligns with IEC 60947-1 overvoltage category III for industrial control circuits — it can handle switching transients from contactor coils and nearby drives without flashover.
Where it is used
This class of thermal overload relay is the standard protection device for three-phase induction motors in industrial automation — found in motor control centers, conveyor drives, pump stations, and compressor skids. The ATEX approval (DMT 98 ATEX G 001) extends its use into potentially explosive atmospheres (Zone 1 or Zone 2 gas groups), so it can be specified for chemical, oil and gas, or grain-handling installations where the relay sits in a certified enclosure.
Mounts stand-alone or directly onto a SIRIUS contactor of matching size S00. The mounting position allows rotation of ±135° on a vertical surface and tilting of ±45° forward/backward — useful when fitting into tight or angled panel layouts. The main circuit uses screw-type terminals accepting solid conductors: 2× (0.5 to 1.5 mm²) or 2× (0.75 to 2.5 mm²), and finely stranded with ferrule the same range. AWG equivalents: 1× (20 to 16), 1× (18 to 14), 1× 12. The auxiliary contacts (0 built-in) are not present on this variant — if you need auxiliary signaling, you add a separate auxiliary switch block.
Operating temperature range -20 to +70 °C, storage and transport -55 to +80 °C. Withstands 100 % relative humidity during operation (non-condensing). Shock resistance 8g for 10 ms. Maximum operating altitude 2 000 m without derating. The part carries ATEX certification for gas atmospheres (DMT 98 ATEX G 001).