The Siemens SIRIUS 3RU5166-5EB1 is a three-pole thermal overload relay sized for motor protection in the S10 frame. It covers a 1.4 to 2 A adjustable current range with Class 10 trip characteristic — that means it will open the contactor within 10 seconds at 7.2× the set current, fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts.
What the ratings mean for fit
The adjustable current response value of 1.4 to 2 A is the setting range for the bimetallic trip element. You set the dial to the motor's full-load amps (FLA) within that window. At 2 A maximum, this relay is sized for small motors — fractional horsepower up to roughly 0.75 kW at 400 V. The 3-pole construction protects all three phases; a single-phase condition on any pole will cause the relay to trip. Screw terminals on both the main circuit and auxiliary circuit mean you land ring or fork lugs directly — no special crimp tooling needed. The S10 frame size is the large physical format in the SIRIUS family; it mounts via screw fixing, not snap-on DIN rail, so plan for a dedicated backplate or mounting channel in the panel. The surge voltage resistance of 8 kV (rated value) means the relay's insulation withstands transient overvoltages typical in industrial power distribution — it won't flash over during a nearby lightning strike or switching surge on a 400 V line.
Lifecycle and sourcing reality
Substance prohibitance date of 09/03/2013 indicates RoHS compliance as of that date. The part carries the SIRIUS brand and is designed for use with S10-frame SIRIUS contactors, typically the 3RT5065 series.
Where it goes in the panel
This overload relay mounts directly to the SIRIUS S10 contactor or can be installed separately as a stand-alone unit. The 50/60 Hz operating frequency covers both 50 Hz and 60 Hz line supplies without derating. The 0 to 100% relative humidity rating means it handles condensing environments — common in washdown areas or outdoor enclosures — as long as the ambient temperature stays within the -25 to +60 °C operating range typical for the SIRIUS family.