Abstract: A subterranean electro-thermal heating system including one or more heater cable sections extending through one or more heat target regions of a subterranean environment and one or more cold lead sections coupled to the heater cable section(s) and extending through one or more non-target regions of the subterranean environment. A cold lead section delivers electrical power to a heater cable section but generates less heat than the heater cable section. The heater cable section(s) and the cold lead section(s) are arranged to deliver thermal input to one or more localized areas in the subterranean environment.

Abstract: Heat tracing of an elongate, thermally-insulated substrate is effected by means of one or more elongate, constant wattage electric heaters mounted in thermal contact therewith beneath the thermal insulation. A metal conduit is mounted on the substrate and extends away therefrom out through the thermal insulation. The or each heater extends from the substrate through the conduit and is connected to a source of electric power within an external junction box. By this arrangement, the heat developed along the length of the constant wattage heater as it passes through the thermal insulation of the substrate can be dissipated safely through the body of the conductive conduit.