What is the Normally Open (NÃO) Thermostat Switch KSD301?

The Thermostat Switch KSD301 bimetallic disc operates in a Normally Open (NÃO) configuration. This means the circuit is initially open (desconectado) at normal temperatures. When the temperature rises to a predefined threshold, the bimetallic disc bends, closing the circuit and allowing current flow.

Normally open THERM-O-DISC T-O-D THERMAL LIMIT SWITCH L160-40F 60TX01

UL/CUL KSD301 Shutoff Thermostat,Normally Open NO Bimetal Snap Disc 125V 16A Auto Reset

uxcell KSD301 Thermostat 40°C/104°F 10A Normally Open N.O Adjust Snap Disc Temperature Switch

EU. Core Features
‌Operation Principle‌
When the temperature rises to the set value, the contact automatically connects the circuit; when the temperature drops to the reset value, the contact automatically disconnects the circuit, which is the opposite of the normally closed type (disconnected when the temperature rises and connected when the temperature drops).

The bimetallic strip is heated and deformed to trigger the mechanism to achieve fast switching.

‌Technical Parameters‌
‌Electrical Specifications‌:
Tensão nominal: AC 250V (carga resistiva) or AC 125V (UL standard)
Corrente nominal: 5A/10A/15A (carga resistiva)
‌Temperature performance‌:
Action range: 0℃~300℃ (personalizável), accuracy ±2℃~±10℃17
Reset and action temperature difference: 8℃ ~ 100 ℃ (adjustable)
‌Mechanical characteristics‌:
Resistência de contato: ≤50mΩ, insulation resistance: ≥100MΩ13
Resistência elétrica: AC 1800V/1min without breakdown
Vida de serviço: ≥100,000 times17 (some models up to 150,000 times2)

‌Physical characteristics‌
Nível de proteção: IP00 (no dust and water resistance)
Método de fiação: terminal de plug-in 250# ou 187# (angle 0°~90° optional)
Método de instalação: supports various structures such as movable ring, flat ring, aluminum cover with holes, etc..

Normally Open State:
The KSD301 is designed to have its contacts in an open state when the surrounding temperature is below the specified operating temperature. This means the circuit connected to the KSD301 is broken, preventing current flow.

Temperature Trigger:
À medida que a temperatura aumenta, the bimetallic disc (made of two different metals bonded together) responds to the temperature change. The two metals expand at different rates, causing the disc to bend.

Circuit Closure:
When the temperature reaches the set point, the disc bends enough to close the circuit, establishing a connection between the contacts. This allows current to flow through the circuit.

Automatic Reset:
Once the temperature drops below a certain level, O disco bimetálico retorna à sua forma original, opening the circuit again and cutting off the current flow. This is an automatic reset feature.
In essence, the KSD301 is used as a thermal switch to control current flow based on temperature, acting as a temperature sensor and protector for various applications.

II. Cenários de aplicação
APLAÇÕES DESHOND APLICAÇÕES‌: dispensadores de água, ThermoMoros elétricos, fornos de microondas, armários de desinfecção, Aquecedores elétricos, máquinas de café, etc..
‌Industrial equipment‌: motor overheat protection, rectifier equipment, laminating machines, car heated seats, etc.57.

Iii. Detection method (determine whether it is normally open)
‌Multimeter detection‌:
À temperatura ambiente (‌below the action temperature‌): the resistance of the two pins should be infinite (open circuit).
After heating (‌above the action temperature‌): the resistance value drops to ‌tens of ohms‌ (open circuit).
‌Marking distinction‌: The product body is usually marked with “NÃO” (Normalmente aberto) ou “Normalmente aberto”.

4. Product advantages
Velocidade de resposta rápida, clean contact action without arcing57;
Precisão de controle de alta temperatura, strong reliability7;
Compact structure, strong adaptability17.

⚠️ Note: The actual selection needs to confirm the specific temperature threshold (such as 85℃, 95℃, etc.) and the reset temperature difference. The parameters of different models may vary.