Solid state relay, 1-phase 3RF2 Width 22.5 mm, 20 A 24-230 V / DC 24 V screw connection Solid state relay SIRIUS 3RF21 for switching resistive/inductive loads, e.g. radiators or valves in a bottling plant. The devices switch wear-free and silently and are therefore ideal for noise-sensitive areas (offices, hospitals). They are extremely reliable even at high switching frequencies. The compact design saves space on the cooling surface. The solid state relays can also be expanded for a wide range of applications by simply clicking on the standardized 3RF29 function modules. The devices are approved worldwide (e.g. IEC and UL/CSA). The solid state relays are available as 1-phase devices in two widths or as 3-phase devices. They are available for various outputs and rated operating voltages. Designed for AC or DC operation, they are available with screw, spring-loaded or ring cable lug connections. In addition to the 3RF29 function modules, control plugs and terminal covers are also available as accessories. Simple, efficient, always up-to-date - the SIRIUS modular system.