A heat trace system (10) is used for heating water to prevent freezing in a conduit (20) while servicing an aircraft positioned at a passenger loading bridge (52). An upstream fitting (26) is attached onto the conduit adjacent to a building structure and a downstream fitting (48) is attached onto the conduit adjacent to the cab of the passenger loading bridge. A coated retractable coiled wire disposed within the conduit and cold lead wires (46) enter through the upstream fitting and leave through the downstream fitting. A low voltage solid state power control box (56) is in communication with the cold lead attached to the coiled wire inside providing regulated electrical energy for heating the coiled wire thus preventing freezing the water within in the conduit.