The Siemens 3RB2016-2SD0 is a SIRIUS solid-state overload relay for three-phase motor circuits, rated CLASS 20E trip class. That CLASS 20E rating means it allows a 20-second cold-start locked-rotor time before tripping — sized for standard induction motors with moderate acceleration profiles like fans or centrifugal pumps, where the inrush decays within that window without nuisance tripping. It mounts directly onto a contactor (contactor mounting), not a DIN rail — so the panel layout needs the contactor footprint already in place. The 3-pole main current circuit uses screw-type terminals; the auxiliary and control circuit uses spring-loaded terminals, which speeds wiring on the control side but means the main power conductors still need a screwdriver.
ATEX and environmental rating
Certified PTB 06 ATEX 3001 Ex II (2) GD — this relay is approved for use in potentially explosive atmospheres (gas and dust) as an associated apparatus, suitable for Zone 1/2 gas and Zone 21/22 dust areas when installed in a certified enclosure. That makes it a fit for chemical, oil and gas, or grain-handling lines where standard overloads would not be accepted. Operating temperature range -25 to +60 °C, with 100 % relative humidity during operation. Shock resistance 15g / 11 ms. Surge voltage resistance rated 6 kV, with burst immunity per IEC 61000-4-4 severity 3 (2 kV on power ports, 1 kV on signal ports).
Auxiliary contact ratings
The auxiliary contacts are rated for switching at multiple control voltages: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, with lower ratings at 60 V (0.55 A), 110 V (0.3 A), 125 V (0.3 A), and 220 V (0.11 A). These are the maximum switching currents — useful when sizing the control transformer or verifying the relay can drive the PLC input or contactor coil it feeds.
Dimensions and mounting clearances
Dimensions: 45 mm width, 64 mm height, 73 mm depth. Mounting position any. Required clearances: 0 mm upwards, forwards, backwards, and downwards; 6 mm at the side. That zero-clearance on four sides means it can be packed tight against other components in the panel — useful when retrofitting into an existing contactor assembly where space is already allocated.