Overview Similar Products –> Product Description 19-SF2-115 Thermal Switch Part 115 degrees F. (1/2 inch disc) 25 amp This can be added to any of the furnace units that do not come with this switch. Simply place it in line with the power, mount the switch on the furnace housing / jacket so that will allow the fan to come on as the fireplace gets hotter and will also turn it off as it cools down. Product Videos Custom Field Product Reviews