CE, UL, CSA. Screw terminals can only be used with screw terminal overloads and spring terminals can only be used with spring terminal overloads. Overload Relay - 3RU range. Switch position indicator and test function STOP button Selector switch for manual/automatic reset Screw connection or Spring-clamp versions Impulse voltage resistance 6 kV Insulation voltage 690V Surface or DIN-rail stand-alone mounts available, see ; 706-1699 706-1699 etc. The 3RU21 thermal overload relays up to 80 A have been designed for current-sensitive protection of loads with normal starting. These thermal overload relays for use with Sirius Size S0 ; S00 Contactors