What is Thermal Fuse and Thermal Switch? Difference


Thermal Fuse and Thermal Switch both are electrical safety devices also known as safety cutoff. In both electrical and electronic circuits, appliances, devices they are used. As its name suggests thermal cutoff, so it will break or cut off the circuit and its operation is related to the thermal operation.

Now let's know what is Thermal Fuse?

The thermal fuse is a safety device that breaks or cuts off the circuit when the temperature surrounding it exceeds the threshold. There are two mechanisms, depending upon which the thermal fuse works. In mechanism one, a small meltable metal pellet holds down a spring. And this spring supports the contact that makes the electrical connection. So when the temperature was raised the pellet got melt and the spring was released. So the circuit or electrical connection is broken and the circuit will be interrupted.

Another mechanism is similar to a normal electrical fuse. That means a single conductive wire joint two different circuits that are to be protected. Now when the surrounding temperature of that wire exceeds the threshold temperature, the wire will be melt and will disconnect the circuit.

what is thermal fuse, symbol



Difference between Thermal Fuse and Normal Electrical Fuse

In a thermal fuse, the fuse element is melted by an external temperature source. So an external temperature surrounding the fusing element will cause to melt the fuse element. on the other hand, in a normal electrical fuse, the temperature is generated by the ohmic heating of the fusing element. That means when excessive current or overcurrent flows through the fusing element heat will produce in that fusing element and more heat will cause to melt the fusing element.


Thermal Fuse Use: Thermal fuses are used in heat-producing devices such as Hair Dryers, Coffee makers, Hot Blowers, portable heaters. Here, the main function of a thermal fuse is to disconnect the main power supply when the temperature exceeds more due to automatic cutoff failure or thermostat failure.


What is Thermal Switch?

A thermal switch is also an electrical safety device that normally opens the circuit when the temperature raises and again recloses the circuit when the temperature goes down. Unlike a thermal fuse, the thermal switch can be reusable. In the thermal fuse, once the fusing element got melt it should be replaced by a new one but in the case of a thermal switch, there are no fusing elements to melt.

There are also two mechanisms the thermal switch works. In the first mechanism, there is a bimetallic strip that is connected to each other in the normal condition. So when the temperature raises bimetallic strip expansion happens and they disconnected from each other. When the temperature decreased, again the bimetallic strips connected to each other.

Another method is PTC Thermistor or Positive Temperature Coefficient Thermistor. Here, when the temperature raises the resistance of the thermistor is increased and blocks the current flow. The PTC thermistor thermal switch does not act as a true switch because in the normal condition also, it provides some resistance to the flow of current.

What is Thermal Switch, Symbol




Thermal Switch Use: Thermal switch is used in Microwave ovens, Refrigerators, Electrical heating, and cooling systems, HVAC devices, clothes dryers, space heaters, etc.


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What is Thermal Fuse and Thermal Switch? Difference What is Thermal Fuse and Thermal Switch? Difference Reviewed by Author on 3/08/2022 Rating: 5
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