Thermistor Motor Protection Relay Compact Evaluation Device with a 17.5 mm housing and screw connection. It features 1 normally closed contact and 1 normally open contact, suitable for AC/DC 24 V with auto-reset. The device is compatible with bimetal switches and has 2 LEDs (READY/TRIPPED) for galvanic isolation. The SIRIUS 3RN2 Thermistor Motor Protection Relay protects motors from overheating through direct temperature measurement. This 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.

By using PTC sensors or bimetal switches, parameterization of the devices is not necessary. The LEDs enable quick fault diagnosis. The devices are climate-resistant, touch-safe, and can be used worldwide 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 DIN rail 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.