What it is and what it does
The Siemens 3RB2016-1NB0 is a SIRIUS solid-state overload relay — a CLASS 10E trip curve device that protects three-phase motor circuits from sustained overcurrent without the thermal lag of a bimetal relay. It mounts directly onto a contactor (contactor mounting), saving DIN-rail space in the panel and keeping the power loop short. The relay carries ATEX Ex II (2) GD certification (PTB 06 ATEX 3001).
Key ratings and what they mean for fit
CLASS 10E means the relay will trip within 10 seconds at 7.2× the set current — fast enough to protect standard squirrel-cage motors during a stall or locked-rotor event, but not so fast that it nuisance-trips on normal starting inrush. The 45 mm width and 64 mm height keep the footprint compact; the 73 mm depth is the projection from the contactor face, so verify clearance to the enclosure door or adjacent devices. Screw-type terminals on both main and auxiliary circuits accept solid conductors from 0.5 to 4 mm² (2× 0.5 to 2.5 mm²) and finely stranded with ferrules from 0.5 to 2.5 mm² — standard panel wire sizes, no special crimps needed. Operating temperature range of -25 to +60 °C covers most indoor industrial environments; the 100 % relative humidity rating means condensation is tolerated as long as it's not continuous immersion.
Integration notes
Mounting position is any orientation, which simplifies panel layout when the contactor is mounted sideways or upside-down. The relay withstands 15g shock for 11 ms — suitable for installation on machine frames or in mobile equipment, not just stationary panels. EMC immunity includes 2 kV burst on power ports and 1 kV on signal ports (severity level 3 per IEC 61000-4-4), plus 6 kV surge voltage resistance — adequate for industrial environments with motor starters and contactors switching inductive loads.