ThermaTrace to the rescue
ThermaTrace cable is self-regulating heating cable. It can be used for frost protection, or to maintain specified temperatures of refrigerant pipes and boilers.
ThermaTrace uses two parallel heating elements, encased in protective silicon, which form insulation and an outer surface of the cable. The heating cable responds automatically to changes in weather. When temperatures increase, the synthetic material expands to reduce the load. When the temperature drops, the load increases. So the heating power varies with the temperature of the surface where the heating cable is installed. These cables do not overheat - even if they overlap.