The Siemens 3RQ4018-2AM08-0AX0 is an output coupler relay from the SIRIUS 3RQ4 family, narrow design. It packs a 24 V DC coil (pick-up range 0.7–1.25 x Us), a single change-over contact, and spring-loaded push-in terminals into a 6.2 mm wide housing — that's the narrowest slice in the SIRIUS coupling relay line, sized for dense DIN-rail panels where every millimeter of rail counts. Rated thermal current is 6 A, meaning the contact path is sized for signal-level loads and small auxiliary circuits — think PLC digital outputs driving contactor coils, indicator lamps, or solenoid valves. The push-in terminal accepts solid or ferruled stranded wire without a tool; strip to 8–10 mm and seat it. No screw torque to verify, no vibration loosening over time.
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At 6.2 mm wide, ten of these fit in the space of one typical 62 mm terminal block — useful for grouping multiple isolated output channels in a single slice. The spring-loaded push-in terminals reduce wiring time compared to screw-clamp variants; no calibration of torque drivers, no re-torquing after thermal cycling. Coil draws from a 24 V DC supply; the 0.7–1.25 x Us range means it holds in at 16.8 V and must not exceed 30 V. If your control voltage sags during motor starting, verify the DC bus stays above dropout. The single change-over contact (1 CO) gives both N/O and N/C paths — useful for signaling back to a PLC input while switching the load.
What the 6 A thermal current means for your load
The 6 A thermal current (Ith) is the continuous current the contact can carry in free air at 40 °C ambient. For resistive loads (AC-1), derating is minimal — you can switch 6 A all day. For inductive DC loads or motor starters, the making/breaking capacity is lower; the contact is designed for pilot duty, not main power switching. If your load is a 24 V DC solenoid pulling 2 A inrush, this relay handles it cleanly. If you're switching a 1.5 kW motor contactor coil, verify the inrush stays under the contact's rated making capacity.