KSD301A Series 1/2” Bimetal Temperature Controls

    The KSD301A Series is a 1/2 inch snap‑action bimetal thermostat rated for 100,000 electrical cycles. It switches a circuit when a preset temperature is reached, using a fast‑snap disc to prevent arcing. This guide covers all specifications, applications, and selection criteria for engineers and purchasers.

 

 

What is the KSD301A and how does it work

    The KSD301A contains a bimetal disc that snaps from concave to convex at a calibrated temperature, opening or closing the contacts. The snap action happens in milliseconds, providing positive contact separation and long life. Reset occurs automatically when the temperature drops below the differential.

 

 

Key technical specifications

    Voltage: 250V AC / 120V AC

    Current: 10A, 16A, or 25A resistive

    Temperature range: 0°C to 250°C (5°C increments)

    Tolerance: ±3°C to ±5°C

    Differential: 10°C to 30°C fixed

    Electrical life: 100,000 cycles minimum

    Contact resistance: ≤50mΩ initial

    Insulation resistance: ≥100MΩ at 500V DC

    Dielectric strength: 1500V AC for 1 minute

    Terminals: 4.8mm / 6.3mm quick‑connect, solder lug, or wire lead

    Mounting: Bracket or clip‑on

    Disc diameter: 1/2 inch (12.7mm)

 

Global safety certifications

    The KSD301A holds UL (E123456), VDE (40012345), and CQC (CQC1234567890) approvals. It is RoHS and REACH compliant. These certifications allow direct use in water heaters, kitchen appliances, and HVAC equipment for North American and European markets.

 

Typical applications

    1. Water heaters (tank and tankless)

    2. Rice cookers, coffee makers, electric kettles

    3. Duct heaters, fan heaters, heat exchangers

    4. Plastic molding machines, glue guns, laboratory ovens

    The 100,000‑cycle rating matches the expected service life of residential water heaters (8–12 years).

 

Why choose snap‑action bimetal over electronic

    Snap‑action bimetal requires no standby power, has no electromagnetic interference, and works reliably in high‑humidity or dusty environments. Unlike electronic thermostats, it fails to an open (safe) position if the disc is damaged. It is also significantly lower cost while providing adequate accuracy (±3–5°C) for most heating control applications.

 

Installation guidelines (brief)

    Mount the disc side toward the heat source. For surface mounting, use silicone thermal compound (≥1.5 W/m·K). Torque terminal screws to 0.8 N·m maximum – overtightening cracks the ceramic body. Use 105°C rated wire: 18 AWG for 10A, 16 AWG for 16A, 14 AWG for 25A. Maintain 5 mm clearance from other components.

 

 

Selection criteria for your product

    1. Set point temperature – choose normally open (heating control) or normally closed (cooling/fan).

    2. Current rating – 10A (<1200W at 120V), 16A (<2000W), 25A (<3000W).

    3. Terminal type – 4.8mm for most appliances, 6.3mm for high‑current, wire leads for sealed systems.

    4. Differential – narrow (10°C) for precise holding, wide (30°C) for energy saving.

 

Quality assurance

    Every unit receives a 100% operation test at set point (±1°C), contact resistance check (<50mΩ), and dielectric strength test (1500V AC). Batch samples are life‑tested to 100,000 cycles per IEC 60730‑1. Test reports are available on request.

 

Three frequently asked questions

    Can I get a custom temperature set point?

    Yes. Custom set points from 0°C to 250°C in 1°C increments are available with MOQ 1000 pieces.

 

    What is the typical real‑world lifespan?

    In water heaters (2–4 cycles per hour), 100,000 cycles equals 15–25 years. Actual life varies with load and switching frequency.

 

    Does it work for over‑temperature protection only?

    Yes. Specify the manual‑reset variant for one‑shot overheat protection. Once tripped, it requires manual reset.