The Siemens 3RF2350-1AA04 is a SIRIUS solid-state contactor, single-phase design, built for zero-point switching of resistive and lightly inductive loads up to 50 A in AC-51 duty class. That AC-51 rating means it's sized for switching resistive heaters, ovens, and similar loads where the current waveform is nearly sinusoidal — not for motor starting or heavy inductive cuts.
The 67 mm width means it occupies three or four standard 18 mm module positions — plan your enclosure rail space accordingly. Side-by-side mounting is allowed without derating gaps, which simplifies panel layout for multi-zone heater banks. Power dissipation in the hot operating state is 54 W; that heat must be vented or accounted for in the enclosure thermal budget, especially when several units are ganged together. Derating begins above 40 °C ambient — above that, reduce the load current per the manufacturer's curve to stay within junction temperature limits.
Both the main current circuit and the auxiliary/control circuit use screw-type terminals. The main terminals accept solid or stranded wire from 1.5 to 6 mm², or two conductors of 14–10 AWG each. The control terminals accept finer wire: 1x 0.5–2.5 mm² solid or 2x 0.5–1.0 mm². The control supply draws 15 mA at the DC rated value, with a control voltage range of 40–506 V AC (50/60 Hz) or 30 V DC — note that the DC control range is narrow, so confirm your control voltage is within that window before wiring. The zero-point switching function means the contactor turns on only when the AC voltage crosses zero, minimizing inrush and EMI on resistive loads; turn-off also happens at zero current, which eliminates arc stress on the contacts but means the load current must drop below the thyristor holding current (10 mA reverse leakage) to commutate cleanly.