Siemens sirius 3rf2 solid state contactors siemens 3rf2320 1aa22 this 20a 24 to 230v ac solid state contactor is from the sirius 3rf23 range features a high power thyristor with high reverse voltage the space saving design features integrated heatsinks and the unit is touch safe without accessories siemens 3rf2320 1aa22 sirius semiconductor contactor 24 230 vac 20a