Thermistor motor protection relay standard evaluation device with a housing of 22.5 mm. It features spring-loaded terminals, 2 changeover contacts, US = AC/DC 24 V, manual/automatic/remote RESET, and is ATEX certified. Equipped with 2 LEDs (READY/TRIPPED), it provides safe galvanic isolation as well as a test/RESET button. It monitors wire breaks and short circuits and is safe against zero voltage.

The SIRIUS 3RN2 thermistor motor protection relay protects motors from overheating, even in explosive environments, through direct temperature measurement with ATEX approval. The direct measurement of the motor winding temperature allows for the protection of a motor under unusual conditions such as heavy starting, braking operation, frequent switching, or insufficient cooling, thus avoiding unnecessary overdimensioning of the motor. The devices can be used in gas or dust explosive areas.

Thanks to the use of PTC sensors, parameterization of the devices is not necessary. LEDs enable quick fault diagnosis. The devices are climate-resistant, touch-safe, and can be used worldwide due to their 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 automatic, 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 DIN rail or for screw mounting with an adapter (accessory), as well as with hard gold-plated contacts. Uniform accessories for all device variants, such as removable terminals, plug-in 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.