What it is and what it does
The Siemens 3RU2116-0JJ0 is a SIRIUS thermal overload relay in size S00, designed to protect motor circuits against prolonged overcurrent by sensing heat buildup in the bimetal strip. It's meant to mount directly onto a contactor — no separate DIN-rail footprint needed — and it carries a Class 10 trip characteristic, meaning it will open the circuit within 10 seconds at 7.2× the thermal setting, which is the standard for standard-duty motor starting (pumps, fans, compressors) where the start-up isn't a long stall.
Ratings and what they mean for fit
The relay is rated for a maximum operating voltage of 690 V and carries auxiliary contact ratings that vary by voltage: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V. The auxiliary contacts are integrated — no separate add-on block required — and the wiring termination for the main circuit uses ring cable lugs (M3 screw size). The auxiliary switch is built in, so you don't need a separate side-mount block for the trip signal or the N/O status.
Mounting and physical fit
The relay measures 70 mm deep, 45 mm wide, and 76 mm high — the standard S00 block size. It fastens via contactor mounting, meaning it clips onto the front of a matching SIRIUS contactor (like the 3RT2 series) without extra brackets. Mounting position is any orientation, and the ambient operating range is -40 to +70 °C, with storage and transport range from -55 to +80 °C. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across most plant-floor conditions. The screwdriver tip required is Pozidriv PZ2 with a shaft diameter of 5 to 6 mm — standard for panel work.