ST-22 is a widely used automatic reset type overheat protector (also known as a temperature switch or thermostat), mainly used to prevent electrical equipment such as motors and transformers from being damaged due to overheating.
Operating temperature range: 70°C – 150°C (common range, some models also support starting at 55°C), with each step increasing by 5°C
Temperature tolerance: ±5°C [citation 1]
Reset temperature difference (ON/OFF) Typically around 30 ± 15°C (i.e., automatically turns on after the temperature drops)
Electrical load: 8A / 125V~ or 5A / 250V~
Contact capacity: Minimum current: 50mA; Maximum instantaneous current: 30A
Electrical lifespan: More than 10,000 times
Main features: Instant closure action, automatic recovery, fully waterproof sealed type, rapid thermal response
Key Features and Selection Tips
Automatic Reset Function: When the device temperature rises to the activation point, ST22 will disconnect the circuit; after the temperature drops by approximately 30°C, it will automatically reconnect the circuit. This is convenient, but it is necessary to assess whether the device allows for automatic restart.
Wide Temperature Range: Multiple rated activation temperatures are provided (such as 55°C, 70°C, 85°C, 150°C, etc.), and you need to select based on the maximum safe operating temperature of the protected equipment.
Sturdy and Durable with Water Resistance: Encapsulated with heat-resistant resin, it has complete waterproof sealing performance, can adapt to humid and vibrating harsh working environments, and can be directly installed on metal components.
No Current Effect Design: The action only responds to temperature changes and is not affected by motor startup current or other impacts, ensuring stable and reliable operation.
Selection and Application Notes
Confirm the operating temperature: It is essential to select the appropriate ST22 operating temperature point based on the insulation class of the protected equipment and the maximum allowable operating temperature, and leave an appropriate margin.
Pay attention to the reset temperature difference: The temperature difference design for automatic reset is related to the temperature state during the equipment’s restart and needs to be considered comprehensively in conjunction with the equipment’s heat dissipation characteristics.
Post time: Sep-26-2025