What it is and what it does
The Siemens 3RU2116-1DC0 is a SIRIUS thermal overload relay — the bimetallic strip type that tracks motor winding heating and trips the contactor when current stays above the set point too long. CLASS 10 means it must trip within 10 seconds at 7.2× the set current, which is the standard for standard-duty induction motors driving pumps, fans, and compressors. Size S00 is the smallest SIRIUS frame, designed to bolt directly to the matching 3RT2 contactor without extra brackets, saving DIN-rail space.
Key ratings and what they mean for fit
Rated insulation voltage is 690 V, so it lives in 400 V and 480 V panels without derating for voltage stress. The auxiliary contact is integrated and carries a note "for message 'Tripped'" — that normally-closed 95-96 contact opens on overload, feeding a PLC or indicator directly. No separate aux block needed. The switching capacity across the aux contact covers 2 A at 24 V and 3 A at 120 V, enough for a 24 VDC PLC input or a 120 V alarm lamp. Spring-loaded terminals accept 2× 0.5 to 2.5 mm² solid or stranded, so the wireman's standard 1.5 mm² motor lead fits without ferrules. Temperature compensation is active from -40 to +60 °C, meaning the trip curve doesn't drift when the relay sits next to a warm contactor in a non-ventilated enclosure.
Mounting and integration
Fastening method is contactor mounting — it clips onto the 3RT2 contactor's front face, not a DIN rail. The relay measures 45 mm wide, 87 mm tall, 70 mm deep, so it adds about 70 mm of depth to the contactor assembly. Any mounting position is allowed, so vertical or horizontal orientation in the panel is fine. The screwdriver slot for the terminal screws takes a 3 mm diameter shaft, 3.0 × 0.5 mm tip — a standard PZ1 or slotted 3 mm works.