The Siemens 3RB1066-2GG0 is a solid-state overload relay from the 3RB10 series, rated 55-250A with trip class 20. It comes with mounting rails designed for direct attachment to 3RT106 contactors or for separate panel mounting. The MOD.S10/S12 designation indicates the modular accessory interface for communication modules or remote reset options.
What the ratings mean for fit
The 55-250A adjustable range covers motor full-load currents from about 55 A up to 250 A. Class 20 trip means the relay allows 600% of the set current for up to 20 seconds before tripping — sized for motors with moderate starting inertia like pumps, fans, and compressors. A class 10 or 10A relay would trip faster and nuisance-trip on higher-inertia starts; class 30 gives more hold time for heavy flywheel loads. For the typical 200 A motor circuit, set the dial to the nameplate FLA and the class 20 curve protects the winding without nuisance trips on across-the-line starts.