System for preventing and clearing ice dams

This invention relates generally to deicing systems and, more particularly, to a system for preventing and clearing ice dams from roof gutters and downspouts. A system for preventing and clearing gutter ice dams includes a plurality of wire holding assemblies, each assembly having a base for attachment to a gutter and a length-adjustable arm for contact with a roof adjacent the gutter. The arm is rotatably and pivotally mounted to the base. The system includes a PTCR heating cable that is held in a desired position by the wire holding assembly arms. The system includes roof and gutter temperature sensors and a moisture sensor. The heating cable is connected to the control unit, the control having a mode selector switch for controlling operation of the cable. In an automatic mode, the heating cable is energized if a roof temperature is greater than a predetermined temperature and a gutter temperature is less than a predetermined temperature. In a timer mode, the heating cable is energized for a selectable time.