One advantage of using self-regulating cable for heat tracing is that it is designed to heat when outdoor temperatures turn cold and 
stop heating when it reaches its maximum temperature. To answer the question, it is important to understand how self-regulating cable works and how it will be used in an application. Self-regulating cable consists of 2 bus wires encased in a semi-conductive graphite core. Typically, there is an inner jacket between the core and a wire mesh which serves as a ground. An outer jacket covers the mesh. When the graphite core is cold, it is more conductive, meaning there are more electrical paths between the two bus wires. This allows for more flow of electricity resulting in generating more heat. As the cable gets warmer, these paths start separating, and the core becomes less conductive. Finally, the core reaches its maximum temperature and electricity only flows through the core to maintain the maximum temperature.
If self-regulating cable self-regulates as described, why use a controller? Consider the application; or what the cable will need to do.
Self-regulating cable is available with different maximum continuous maintenance temperatures ranging as high as 150°F to 250°F. If the cable is heating a pipe with fluid to reduce its viscosity and the fluid is not temperature sensitive, higher temperatures may not be an issue. If the application is freeze protection, heat produced by the cable above the freezing point is wasted energy. Imagine paying electric bills for freeze protection during the hot summer months. A temperature controller will stop the flow of electricity once the cable reaches the programmed set point. Not only will this save money, but it will also extend the life of the cable.
The Temperature Superstore sells ETI temperature controllers and snow switches designed for use with BriskHeat SLCBL Self-Regulating heating cable. Tracon Heat Trace Control thermostats can be programmed with set points to control temperatures in the desired range. Single and dual zone units are designed for outdoor use. Snow Switch Snow & Ice Controls include ground fault and provide power to SL cable when Snow Switch sensors detect snow or ice. BriskHeat SLCBL is moisture and chemical resistant, and available in 3, 5, 8, 10 and 12 watts per foot. All items are in stock and can be shipped out within a couple days.
No Self-Regulating heating cable installation is complete without insulation to hold in the heat. BriskHeat Silver Series insulators are durable cloth insulators designed to fit straight pipe or tubing, and fittings such as elbows and tees. Made with polymer-coated fiberglass cloth, they have an ingress rating of IP54, and a thermal protection rating of R3.3. The Temperature Superstore also carries a full line of Owens-Corning and Johns Manville pipe insulators made with fiberglass, perlite or calcium-silicate in various thicknesses.
