What it is and what it does
The Siemens 3RU1116-0KB0-ZX95 is a SIRIUS thermal overload relay in the compact Size S00 frame, designed to protect three-phase motor circuits against overload and phase-loss conditions. It mounts directly to a contactor (contactor mounting per the spec) and its Class 10 trip characteristic means it will open the circuit within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a stalled-rotor event.
Key ratings and what they mean for fit
The relay is rated for 3 poles on the main current circuit, with screw-type terminals on both main and auxiliary/control circuits. The auxiliary contacts are rated at 1 A at 24 V, 3 A at 120 V, 2 A at 230 V, and 1 A at 400 V — these are the switching capacities for the N/O and N/C signalling contacts that feed the PLC or motor starter feedback loop. The 6 kV surge voltage resistance (rated value) means the auxiliary circuit can handle transient overvoltages typical in industrial control panels without flashover. Power dissipation is 1.9 W per pole, so at full load the relay dumps about 5.7 W into the enclosure. In a densely packed panel with multiple starters, that heat adds up — plan for ventilation or derating if ambient inside the cabinet exceeds 40 °C. The operating temperature range is -20 to +70 °C, with storage and transport range of -55 to +80 °C. The IP20 protection on the front means it's finger-safe against accidental contact (touch protection per the spec), but it is not sealed against dust ingress or moisture — this is a panel-mounted device, not a field-mounted one. The ATEX certification (DMT 98 ATEX G 001) allows installation in potentially explosive gas atmospheres, which is a key differentiator for chemical, oil and gas, or grain handling applications.
Mounting and clearances
The relay fastens via contactor mounting — it snaps directly onto the matching SIRIUS contactor (e.g., 3RT2 series in Size S00). The mounting position is flexible: it can be mounted on a vertical surface with ±135° rotation or ±45° tilt forward/backward. Clearance requirements are tight: 0 mm upwards, forwards, backwards, and downwards; only 6 mm at the side is needed. This zero-clearance stacking on four sides means you can pack starters side-by-side without breathing room, which is useful for high-density MCC designs. Dimensions are 45 mm wide, 87 mm high, and 78 mm deep — the depth is the critical dimension when planning the depth of the enclosure backplate to cover clearance for the contactor/relay assembly.
Wiring and conductor sizes
The screw terminals accept solid conductors: 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²). For finely stranded wire with ferrule processing, the same cross-section ranges apply. For AWG, the auxiliary contacts accept 2x (20 to 16) and 2x (18 to 14). The relay is rated for 100 % relative humidity during operation, so condensation-prone environments are acceptable as long as the IP20 front is respected.
Compliance and documentation
The relay carries a substance prohibition date of 07/01/2006, aligning with RoHS compliance. The reference code per IEC 81346-2 is F (protective device). Shock resistance is rated at 8g for 10 ms, suitable for standard industrial vibration environments. The ATEX certification (DMT 98 ATEX G 001) is a key compliance document for hazardous-area installations.