What it is and what it does
The Siemens 3RU2116-1CB0-ZX95 is a SIRIUS thermal overload relay in size S00, designed to protect motors against overload and phase failure by monitoring motor current and tripping the associated contactor when the Class 10 trip curve is exceeded. It mounts directly onto a contactor, using the contactor mounting fastening method, and connects via screw-type terminals on the main current circuit. The auxiliary switch is integrated, with 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, among others — so you can confirm signal integrity at the control voltage your PLC or safety relay actually runs.
Key ratings and what they mean for fit
Trip Class 10 means the relay must trip within 10 seconds at 7.2× the current setting — this is the standard for standard-duty motor starting where the load accelerates quickly (pumps, fans, compressors). If your application has a long acceleration time (high-inertia loads like centrifuges), a Class 20 or 30 relay would be needed to avoid nuisance tripping. Rated insulation voltage is 690 V, which covers 400 V and 480 V systems with headroom. The motor power ratings at those voltages are 0.75 kW at 400 V, 1.1 kW at 500 V, and 1.5 kW at 690 V — so for a 0.75 kW motor on a 400 V line, this relay is correctly sized. The auxiliary contact ratings are not all the same — at 24 V it switches 2 A, but at 125 V it drops to 0.22 A. If you're feeding a 24 VDC PLC input, the 2 A rating is fine; if you're switching a 125 VDC control circuit, the 0.22 A limit means you cannot parallel multiple loads on one contact.
Where it goes and how it mounts
Size S00 is the smallest SIRIUS frame — 45 mm wide, 76 mm high, 70 mm deep — designed to mount directly onto a SIRIUS contactor of the same frame size. No DIN rail required; the relay clips onto the contactor and the contactor carries the panel mounting. Mounting position is any orientation, which helps in tight enclosures. The screw terminals accept 2× (0.5 to 1.5 mm²) or 2× (0.75 to 2.5 mm²) solid or stranded wire, with a Pozidriv PZ 2 screwdriver tip and a shaft diameter of 5 to 6 mm. Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across the typical panel ambient range. Storage and transport range is -55 to +80 °C.
Lifecycle and sourcing reality
The 3RU2116-1CB0-ZX95 carries a substance prohibitance date of 10/01/2009, which aligns with early RoHS compliance. For current RoHS/REACH declarations, request the manufacturer's compliance documentation at quote time.