Unfortunately there's no set answer for this because it depends on many factors such as the diameter of the pipes, the installation density of the heating cables, the outdoor temperature, the installation of thermal insulation sleeves, etc.
There are too many variables to provide an accurate answer. Even though this product is designed to keep pipes from freezing, it is not designed to thaw pipes. If your pipe has frozen with the heat tape installed and energized, please check the placement of the built-in thermostat and verify that the insulation has been properly installed and waterproofed.