text: A constant wattage cable is composed of multiple constant electric power zones and is made by wrapping a fine heating element around two insulated parallel bus wires, then on alternating sides of the conductors a notch is made in the insulation.  The heating element is then normally soldered to the exposed conductor wire which creates a small heating circuit; this is then repeated along the length of the cable. There is then an inner jacket which separates the bus wires from the grounding braid. In commercial and industrial cables, an additional outer jacket of rubber or Teflon is applied.
  The benefits of this system over series elements is that should one small element fail then the rest of the system will continue to operate, on the other hand damaged sections of cable (usually 3 ft span) will stay cold and possibly lead to freeze ups on said section. Also, this cable can be cut-to-length in-field due to its parallel circuitry, however, due to the circuit only running to the last zone on the cable, when installing on site you normally have to install slightly beyond the end of the pipe work.  When installing constant wattage, or any heat tracing cable, it is important to not overlap or touch the cable to itself as it will be subject to overheating and burnout. Constant wattage cable is always installed with a thermostat to control the power output of the cable, making it a very reliable heating source.
  The disadvantage of this cable is that most constant wattage cables do not have soldered connections to the bus wires but press on type contact and are therefore more prone to have cold circuits due to loose connections caused by cable manipulation and installation.