What this relay is and what the ratings mean
The Siemens 3RU5166-5GB1 is a SIRIUS thermal overload relay sized for motor protection in the 2.2 to 3.2 A range — Class 10 trip curve, meaning it will open the contactor within 10 seconds at 7.2× the current setting, which is the standard for protecting standard induction motors during a locked-rotor event. Three poles for the main current circuit, screw terminals on both the main and auxiliary circuits, and a manual or automatic reset option — this relay mounts directly to a SIRIUS contactor or can be used standalone with a DIN-rail adapter. Rated operational current of 3.2 A at 50/60 Hz, with an 8 kV surge voltage resistance — that surge rating tells you the insulation coordination is sized for industrial environments with pollution degree 3 (conductive dust or humidity), so it holds up in a typical panel without additional suppression on the line side.
Compliance documentation
Substance prohibitance date of 09/03/2013 aligns with RoHS and REACH compliance milestones — the relay meets the EU substance restrictions that went into effect around that date. The SIRIUS series carries UL, CSA, and CE approvals as standard for the platform, though the specific listing for this order code does not enumerate each mark individually.