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S01 90℃ Normal Close Thermal Protector

S01 Button type is snap action and bimetallic thermostat, Bimetal trips off or on quickly to open or close the circuit when temperature reaches the prescribed value.

Product Details:


A normal close thermal protector, also known as a normally closed thermal switch or NC thermal protector, is a type of thermal protection device that is normally in the closed position, allowing current to flow through the circuit. However, when the temperature reaches a specific threshold, the thermal protector opens the circuit, interrupting the flow of current and providing protection against overheating.

Here are some key features and considerations regarding normal close thermal protectors:

  1. Operation: A normal close thermal protector is typically closed under normal operating conditions, meaning it allows the electrical current to pass through. This allows the protected device or equipment to function as intended. However, when the temperature exceeds the predetermined threshold, the thermal protector reacts to the heat and opens the circuit, preventing further current flow.
  2. Temperature Sensing: Normal close thermal protectors employ temperature-sensitive materials, such as bimetallic discs or pellets, which bend or deform when exposed to excessive heat. This change in shape triggers the opening of the circuit contacts, providing the necessary protection. The specific temperature at which the thermal protector activates can vary depending on the model and application.
  3. Resettable vs. Non-resettable: Normal close thermal protectors can be either resettable or non-resettable. Resettable thermal protectors automatically reset once the temperature drops below the threshold, restoring the electrical connection. Non-resettable thermal protectors, on the other hand, remain open even after the temperature decreases and typically require replacement.
  4. Applications: Normal close thermal protectors find applications in various electrical and electronic devices where overtemperature protection is required. They are commonly used in motors, transformers, solenoids, heating elements, and other components that generate heat during operation. Normal close thermal protectors help prevent overheating, protect against damage, and enhance safety in these devices.
  5. Considerations: When selecting a normal close thermal protector, it is important to consider factors such as the temperature rating, response time, current capacity, and compatibility with the application’s voltage and electrical specifications. Manufacturers typically provide guidelines and specifications for proper selection and installation of their thermal protectors.

Normal close thermal protectors are critical safety components that provide reliable protection against overheating in electrical devices and systems. By monitoring and responding to temperature changes, they help prevent damage, prolong equipment lifespan, and reduce the risk of fire hazards.

Special Features

* Small size and easy for mounting;

* Low current sensitivity, no large temperature difference due to over current;

* Precise temperature control.

Electrical Specifications

250V AC : 3A

125V AC : 6A

24V DC: 6A

Contact Resistance: <30mΩ

Dielectric Strength: 2KV

Technical Parameters


Operating Temperature 60~220℃, A specification for each 5℃
Operating Temperature Tolerance ±5℃
Reset Temperature Less than 1/3 of operating temperature
Reset Temperature Tolerance ±15℃





Curtain Motor

Washing Machine Motor




TUV:R 50383352 0001


Dimensional Drawings



Series Application





1. Can I get a customized thermal protector from you?

Yes. We are providing customized service for our noble customers. If you need a customized thermal protector sample, please kindly tell us the following parameters:

1) Rated voltage and Current

2) Action temperature

3) Dimensional requirements

4)Overloading or Tripping current if needed

5) Application and relevant special demands

6) Potential order quantity.

If the customized thermal protector has the same dimension as our current models, and you only need special parameters, we would not charge any cost for 5 pcs samples. If the requested dimensions are different, we may need to build new toolings for this customization. It would cause extra cost and we can negotiate separately.

2. What parameters should I provide when I am trying to ask for thermal protector samples?

If you need to have temperature sensitive thermal protector samples, please prepare the following parameters:

1. Rated voltage, current

2. Action temperature of thermal protector

3. Leadwire length, type and temperature rating.

4. Application of thermal protector.

5. Mounting requirements if needed, including dimensional requirements.

If you want to have current sensitive thermal protector samples, you may prepare three more parameters besides the above:

1. Trip off current

2. Trio off time

3. Normally working temperature of thermal protector. It can not trip off under this temperature.

3. When and why do we need gold contacts of thermal switch?

1. If you need the contact resistance of thermal switch is less than 15 mOhm, you need gold contacts. The resistance of gold contacts is much smaller than silver contacts.

2. If the rated current of thermal switch is 250 mA or less, Gold contacts are necessary.  It can prevent oxidation of the contacts at low current rating. Oxidation forms an insulation film on the silver contacts and low current does not arc enough to burn off the oxidation.

4. How can we conduct the incoming test for your thermal switch?

Incoming test for thermal switch includes temperature test under No-Load, mock-up test under load, functional test in applications and appearance inspection. Since mock-up test, functional test and appearance inspection can be easily done in the customers’ factories, we will only explain how to conduct temperature test under No-Load here.

1. Put the thermal switch inside of a test oven. The air flow speed of the oven needs to be over 200m/min

2. The measuring thermal couple should be as close to thermal switch as possible. An indicator of showing ON/OFF should be provided. The current flowing through thermal switch is less than 0.01A

3. Increasing the air temperature inside of the oven slowly. When air temperature increases to the 10C lower than the bottom tolerance limit of rated temperature value, the further temperature increasing speed has to be controlled at 0.5K/min.

4. When the temperature reaches the tolerance of thermal switch, the bimetal will actuate the contact and cut the circuit off. After that, the operator can open the cover of test oven and let the temperature decrease down. Then, the thermal switch will turn ON again.




Contact Information

Company Name: Yangzhou Wuyue Electric Co.,Ltd

Address:Building D, Software Information Industrial Park, No.2 Huaijiang Avenue, Baoying County, Jiangsu Province, China

Contact: Lorena Qiao

Mobile: +86 153 6641 6606 / 189 2191 2633

Tel: +86 514 88986588

Fax:+86 514 8898 6599