The Siemens 3RF2170-1AA06 is a SIRIUS-brand single-phase solid-state relay rated for 50 A in AC-51 duty (resistive load), with zero-point switching to minimize inrush and EMI on turn-on.
The 50 A AC-51 rating is the resistive load curve — this SSR is sized for steady-state current, not motor starts. The minimum operational current of 500 mA means it won't reliably switch below that; don't use it for dry-contact signal loads. Zero-point switching turns the load on only at the AC voltage zero crossing, which cuts the radiated hash that phase-angle-fired SSRs generate. The ON and OFF delay times are 1 ms plus a maximum of one half-wave — fast enough for most process control loops, but not for sub-cycle precision. The I²t maximum of 6,600 A²·s and reverse thyristor current of 10 mA are the numbers your fuse selection needs to beat. Siemens recommends NH fuses like 3NA6812-6, sized below the relay's rating to protect the semiconductor junction. Derating kicks in above 40 °C ambient; the 94 W power loss at full load (94 VA) has to be shed into the panel air.
Screw-type terminals on both main and control circuits accept 1x (0.5 to 2.5 mm²) or 2x (0.5 to 1.0 mm²) solid/stranded for the control side, and 1.5 to 6 mm² (or 2x 14-10 AWG) for the power loop.