What it is and what the ratings mean
The Siemens 3RB2016-2PD0 is a SIRIUS solid-state overload relay — three-pole, CLASS 20E, with one NC auxiliary contact and screw-type main terminals plus spring-loaded auxiliary/control terminals. CLASS 20E means the relay will trip within 20 seconds at 7.2× the motor's full-load current, a standard protection curve for general-purpose induction motors driving pumps, fans, and conveyors where start-up transients are moderate. The ATEX approval (PTB 06 ATEX 3001 Ex II (2) GD) qualifies it for use in potentially explosive atmospheres as a protective device associated with category 2 equipment — a key check for panel builders in Zone 1 or Zone 21 environments.
Auxiliary contact ratings and wiring
The single NC auxiliary contact is rated for 2 A at 24 V, 4 A at 120 V, and 3 A at 230 V — these are the continuous thermal current values, so the contact can handle the typical PLC input or contactor coil draw at those voltages without derating. The spring-loaded terminals accept 2× (0.25 … 1.5 mm²) solid or finely stranded wire, or 2× AWG 24–16 for the auxiliary circuit; the main circuit uses screw-type terminals. That split means the power wiring is torqued down and the control wiring is a quick push-in — a common panel-build workflow that saves time on the auxiliary side.
Mounting and environment
Fastening method is contactor mounting — it clips directly onto the front of a corresponding SIRIUS contactor (no DIN rail needed for the relay itself), which saves one DIN-rail slot per motor starter combo. The relay itself is 45 mm wide, 64 mm tall, and 73 mm deep. It can be mounted in any position, and the operating temperature range is -25 to +60 °C with 100 % relative humidity allowed — fine for non-condensing washdown areas inside a rated enclosure. Shock resistance is 15g / 11 ms, adequate for most industrial machinery.
EMC and surge robustness
Surge voltage resistance is rated at 6 kV, and the unit withstands burst transients of 2 kV on power ports and 1 kV on signal ports per IEC 61000-4-4, severity level 3. That level of immunity is typical for industrial control panels connected to a 400 V distribution network without dedicated surge protection on every branch — it means the relay won't nuisance-trip or latch up from nearby contactor switching or VFD PWM noise.