KSD9700/BK05-BB1D Metallic Shell Temperature Control Switch 5A 250V (145°C Normally Open)

This switch is rated for 5 Amps at up to 250 Volts AC or DC. It features a Normally Open (NO) contact configuration, meaning the circuit is open at ambient temperature and will close only upon manual reset after the bimetallic disc cools down below its reset point, which is typically several degrees below the 145°C trip temperature.

Installation involves mechanically securing the metallic body of the switch to the heat source (e.g., motor housing or heatsink) using its mounting lugs or thermal adhesive for optimal thermal coupling. Electrically, connect the two pre-attached lead wires in series with the load (e.g., the motor or transformer winding) you wish to protect. Ensure the switch's current rating (5A) is not exceeded.

This is an automatic reset switch. It utilizes a snap-action bimetallic disc that opens the contacts at 145°C. Once the temperature cools down below its reset point (typically around 15-30°C below the trip point), the disc snaps back, automatically closing the contacts to restore power. This hysteresis prevents rapid cycling.

Standard bimetallic thermostats like the KSD9700 series typically have a trip temperature tolerance of ±5°C. The mechanical snap-action mechanism is designed for a long operational life, often rated for tens of thousands of cycles under its rated electrical load, making it suitable for long-term protective applications.