Electrical Mini Circuit Switch 12V Thermal Fuse

As the name suggests, thermal cutoff devices cut off power as a result of temperature rise. These are often integrated into the body of equipment to protect against overheating.

Technically, an temperature fuse is also a type of thermal cutoff device because when it blows it opens the connection to power. However, industry excludes this ordinary fuse from the list of temperature cutoff devices because thermal fuses are slightly more sophisticated. They consist of a spring held tight mechanically at one end and soldered at the other end to an alloy. If the equipment heats beyond the desired temperature, the solder melts and releases the spring to interrupt power. The temperature of operation depends on the alloy. This process is an example of one-time use thermal cutoff devices.

The positive temperature coefficient (PTC) thermistor is a thermal cutoff device that resets when given a chance to cool down. The polymer PTC resettable fuse is a faster device than the thermistor.

The bimetallic thermal switch is another type of thermal cutoff switch that automatically resets itself. Household appliances such as clothes irons, automobiles turn signals and flashing Christmas lights all use the bimetallic switch. Household refrigerators may use two types of thermal switches: one that cuts off cooling, and the other that cuts off heating.

A manual reset thermal switch is preferred in applications where unattended resetting may be hazardous.