Thermal cutoffs are an excellent safety feature in certain electronic circuits, but their functionality can be lost if not installed correctly. This post will explain the proper installation for thermal cutoffs.
Many devices which generate heat as a part of their functionality, such as coffee makers, microwaves, and certain transformers, to name a few, will have a safety feature in them which will open a circuit in the case of overheating to avoid fire or damage if a malfunction were to occur. The device that is most often used in these applications is called a thermal cutoff or thermal fuse. Click here to view Digi-Key’s selection.
It is important to note that the thermal cutoff must be placed in series with the power source of the device and also near the heat source in order to function correctly. If the thermal cutoff is not close enough to the heat source, damage may occur before the thermal cutoff trips the circuit. If the thermal cutoff is placed in parallel, instead of in series, it will trip at the given temperature but will not open the power circuit allowing damage to occur and defeating the purpose of the thermal cutoff.
Lastly, a thermal cutoff also has a current rating and must be selected above the functional current of the circuit. For example if the circuit draws 6A of current, a thermal cutoff of 10A would be ideal.
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