KSD9700 250V 5A Metal Thermostatic Temperature Switch NC-55° C

KSD9700 250V 5A Metal Thermostatic Temperature Switch NC-55°C serves as a high-reliability thermal protection device designed to safeguard electrical equipment from overheating damage. This bimetallic thermostat operates on a Normally Closed (NC) principle, meaning it maintains electrical continuity under standard conditions. Consequently, when the ambient temperature reaches the critical threshold of 55°C, the internal bimetallic disc snaps open to interrupt the circuit and prevent potential thermal runaway. The rugged metal casing ensures rapid thermal conductivity and superior mechanical strength compared to plastic alternatives. Furthermore, the compact form factor allows you to easily integrate this switch into tight spaces within motor windings or appliance housings. Therefore, choosing the KSD9700 series provides a cost-effective and autonomous safety layer for your power-sensitive electronic designs.

Key Features:

• Normally Closed Operation: The switch keeps the circuit active until the temperature hits the set point, acting as an automatic thermal cutout.
• High-Speed Response: The high-sensitivity bimetallic element reacts quickly to temperature fluctuations, ensuring prompt system protection.
• Durable Metal Housing: A robust metallic enclosure provides excellent heat transfer and protects the internal mechanism from physical impact.
• Automatic Reset: Once the temperature drops below the reset differential, the internal contacts automatically close to restore power to the load.
• Pre-Wired Design: The module comes with heat-resistant lead wires, which simplifies the installation process in industrial environments.

Technical Specifications:

• Switching Temperature: 55°C ±5°C
• Contact Type: NC (Normally Closed)
• Maximum Voltage: 250 V_AC
• Maximum Current: 5 A
• Insulation Resistance: ≥ 100 MΩ (at 500 V_DC)
• Contact Resistance: ≤ 50 mΩ
• Dielectric Strength: ≥ 1500 V_AC for 1 minute
• Service Life: ≥ 10,000 Cycles (at rated load)

Mechanical Specifications:

• Case Material: Stainless Steel / Tinned Copper
• Lead Wire Material: UL-certified high-temperature silicone or PVC insulated wire
• Lead Wire Length: ≈ 70 mm
• Sealing: Epoxy resin sealed for moisture and dust resistance.

Dimensions:

• Body Length: ≈ 20 mm
• Body Width: ≈ 7.4 mm
• Body Height: ≈ 3.8 mm
• Wire Gauge: 20 AWG to 22 AWG (Typical)

Pinout and Wiring:

• Wire 1 (Input/Line): Connect to the incoming power source or the control signal line.
• Wire 2 (Output/Load): Connect to the device or load that requires thermal protection.
• Wiring Note: However, ensure that the total current does not exceed the 5A rating to avoid premature failure of the bimetallic contacts. Because this is a non-polarized switch, you can use either wire for the input or output.

Datasheet Reference:

• Download KSD9700 Series Thermal Switch Datasheet

Commonly Used in:

• Electric Motors: Engineers frequently embed these switches into AC motor windings to prevent burnout during stall conditions.
• Battery Packs: Used as a safety cutoff in Lithium-ion or NiMH battery chargers to detect excessive heat during charging cycles.
• Household Appliances: Found in coffee makers, toasters, and hair dryers for primary or secondary fire protection.

Applications:

• Transformer Protection: Monitors the core temperature of power transformers to prevent insulation breakdown.
• Ballast Safety: Acts as a thermal interrupt for lighting ballasts in commercial fixtures.
• Industrial Heating: Regulates or limits temperature in small-scale heating elements and laminating machines.

Equivalent Models:

• BW-9700: A highly similar bimetallic thermal protector often used as a direct substitute in motor protection.
• ST-22 Series: A plastic-cased alternative that offers similar 55°C NC trip characteristics for less demanding environments.
• KSD301 (Manual/Auto Reset): However, this model features a larger “snap-disc” circular package which may require more mounting space.

Package Includes:

• 1 x KSD9700 250V 5A Metal Thermostatic Temperature Switch (NC-55°C)