Siemens 3RU1136-4FB0 Relay

Siemens 3RU1136-4FB0 is a Sirius size S2 thermal overload relay designed to mount on compatible contactors to protect three‑phase motors from overload. It provides a 28–40 A main current rating with 1 normally open and 1 normally closed auxiliary contact (1NO+1NC) and offers manual‑ or automatic‑reset operation via screw terminals on both the main and auxiliary circuits. The device features 690 V insulation, 6 kV surge withstand, IP20 front protection (finger‑safe), and a typical power loss of 9 W, rated for operation from −20 to +70 °C and up to 2,000 m above sea level. This relay is part of the SIRIUS family and is intended for mounting on size S2 contactors; its modern successor is 3RU2136-4FB0 in the 3RU2 line. With Class 10 thermal protection, it provides reliable motor overload protection in industrial panels while offering straightforward monitoring through its auxiliary contact and screw-terminal wiring.