Thermistor Motor Protection Relay Compact evaluation device with a 17.5 mm housing, spring-loaded terminal, 1 normally closed contact and 1 normally open contact. Supply voltage = AC/DC 24 V, auto-reset suitable for bimetal switches. Equipped with 2 LEDs (READY/TRIPPED) and galvanic isolation. The SIRIUS 3RN2 thermistor motor protection relay protects motors from overheating through direct temperature measurement. The direct measurement of the motor winding temperature allows for the protection of a motor even under unusual conditions such as heavy starting, braking operation, frequent switching, or insufficient cooling, thus avoiding the need for precautionary oversizing of the motor. The use of PTC sensors or bimetal switches eliminates the need for device parameterization. LEDs enable quick fault diagnosis. The devices are climate-resistant, touch-safe, and suitable for worldwide use thanks to a wide voltage range and international approvals. They are available as mono- or bistable evaluation devices, with or without ATEX certification, with one or two sensor circuits, and with auto, manual, and/or remote reset. The devices are available in screw or spring-loaded technology (Push-In). There are versions with a width of 17.5 mm or 22.5 mm, for TH35 mounting rails or for screw mounting with an adapter, as well as with hard gold-plated contacts. Uniform accessories for all device variants, such as detachable terminals, insertion tabs, and coding pins, simplify selection and inventory management. The thermistor motor protection relays 3RN2 replace the proven series 3RN1. SIRIUS relays - a program for all cases.