Abstract

A thermal actuator includes a thermal detector, an actuator unit and a connecting circuit for electrically connecting the thermal detector and the actuator unit. When a second contact member is normally remained uncontact with a first contact member of the thermal detector, the thermal actuator is an open circuit and not function. However, when the second contact member bends to contact with the first contact member due to an overheated or over-cold temperature around the thermal detector, the thermal actuator is in a close circuit and the electric current flows to an actuator unit thereof. A heat wire wrapped around an actuating piece of the actuator unit generates heat to increase the temperature around the actuating piece. When the temperature around the actuating piece increases to a predetermined extent, the actuating piece bends so as to provide an actuating action. If the actuator unit is installed close to a switch or a breaker, the actuating action of the actuating piece can activate the switch to turn off or the jumper of the breaker to cut the electric supply.