I. Overview KSD301 is the most versatile disc-shaped bimetallic snap-action thermostat switch, commonly known as “temperature protector/thermostat”, featuring automatic reset, high current, and insulated housing, widely used in household appliances and industrial equipment.
II. Operating Principle Core: The disc-shaped bimetallic strip senses temperature. When the temperature rises to the set value, it instantly snaps and deforms, triggering the contact action (opening/closing).
Cool down to the reset temperature (about 10–30℃ lower than the operating temperature) → metal plate rebounds → contacts return to their original state, automatically resetting.
Contact form: Normally closed (NC) (default, disconnected upon overheating), normally open (NO) (connected upon overheating).
III. Model and Specifications (Commonly Used) Example Model: KSD301 85℃ NC (Normally Closed, disconnects at 85℃).
Operating temperature: 30℃～250℃, commonly used: 55/65/75/85/95/105/120℃; every 5℃ as a step.
Temperature tolerance: ±2℃, ±3℃, ±5℃ (commonly used ±3℃).
Reset temperature difference: 10~30℃ (e.g. disconnect at 85℃ → reset at about 65℃).
IV. Electrical Parameters (Resistive Load) Rated Voltage: 250VAC; 125VAC; 24VDC.
Rated current: 5A/10A/16A @250VAC; 15A @125VAC.
Contact resistance: ≤50mΩ.
Insulation resistance: ≥100MΩ.
Voltage resistance: ≥1500VAC for 1 minute.
Lifespan: ≥10,000 cycles (AC).
Shell material: bakelite (≤160℃), PPS (≤220℃), ceramic (≤300℃).
V. Structure and Installation Appearance: round piece + dual ear mounting holes, with a diameter of approximately 20mm, a thickness of approximately 4mm, and two foot inserts.
Installation: The metal surface should be tightly attached to the heating element (coated with thermal conductive silicone grease) and secured with M3 screws; the pins should be connected to terminals or soldered.
Features: small size, flexible installation, strong anti-interference, and no arcing.
- KSD301 vs KSD 01F (Key Differences)
KSD301: dual-lug disc, high current (10–16A), wide temperature range (30–250℃), a mainstay in home appliances.
KSD 01F: TO 220 encapsulated, low current (1.5–3A), low temperature (≤150℃), commonly used in PCB/power supply. - Typical Applications: Kitchen Appliances: Disinfection cabinets, electric kettles, rice cookers, microwave ovens, and electric ovens.
Bathroom equipment: water heater, fan heater, bath heater.
Industry / Power Supply: Overheat protection for frequency converters, motors, power modules, and high-power equipment.
Others: water dispensers, clothes dryers, electric irons, car seat heaters. - Selection points 1. Contact type: normally closed (NC) (overheat disconnection, protection) or normally open (NO) (overheat closure, alarm).
- Operating temperature: Select based on the maximum allowable temperature of the equipment (e.g., 85℃ is commonly used for water heaters).
- Load current: Not exceeding 16A at 250VAC.
- Shell material: For high temperatures (>160℃), choose ceramic or PPS; for low temperatures, choose bakelite.