The Siemens 3RU2116-1HC0 is a SIRIUS thermal overload relay, size S00, designed to protect motors against overload and phase failure. It is a Class 10 trip device, meaning it will trip within 10 seconds at 7.2× the set current, which is the standard for standard-duty induction motors — fast enough to protect the winding but slow enough to ride through normal starting inrush. The relay mounts directly to a contactor (contactor mounting) and uses spring-loaded terminals for the main current circuit, which speeds up panel wiring and eliminates the need for periodic screw retorquing.
Key ratings and what they mean for fit
The relay is rated for a maximum operational voltage of 690 V, with an AC-3e rated value maximum of 690 V — this is the voltage class for standard three-phase motor circuits up to 690 V line-to-line. The motor power ratings are given at several common voltages: 3 kW at 400 V, 4 kW at 500 V, and 5.5 kW at 690 V. At 480 V and 600 V, the current rating is 8 A. These are the values you use for BOM matching: if your motor is 3 kW on a 400 V supply, this relay is correctly sized. The auxiliary switch is integrated and carries a note "for message 'Tripped'" — meaning the built-in auxiliary contact signals the tripped state, not just the normal/overload status. This is useful for PLC or HMI annunciation of a thermal trip without needing a separate auxiliary block. The switching capacity varies by voltage: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.75 A at 690 V. These are the maximums for the auxiliary contact; stay within them for reliable signalling. The relay has temperature compensation from -40 to +60 °C, meaning the trip curve stays accurate across that ambient range — important for panels in unconditioned spaces or near process heat. The operating temperature range is -40 to +70 °C, with storage and transport from -55 to +80 °C. The MTTF with high demand rate is 2,280 years, which supports use in safety-related applications where reliability data is required for SIL calculations.
Mounting and integration
Size S00 is the smallest SIRIUS overload relay frame, with dimensions 45 mm wide, 87 mm high, and 70 mm deep. It mounts directly to a contactor (contactor mounting) in any position. The spring-loaded terminals accept 2 × (0.5 to 2.5 mm²) solid or stranded wire. For the auxiliary screw terminals, use a screwdriver with a 3 mm diameter shaft and a 3.0 × 0.5 mm tip. No DIN rail adapter is required if mating to a contactor; if used standalone, a separate mounting base is needed.