The Effects of Sunlight on Vertical Conduits

Interior vs. Exterior

• The interior temperature of outdoor conduits is often ignored when they are measured for electrical ampacity. In general, regulations consider the ambient temperature for a conductor to be the same as the surrounding air. Conduits often get hotter inside than the outside air, though. Ignoring the effect of temperature can overheat the system and cause damage to or failure of the electrical cables inside the conduits.

Effect of Color

• One major factor that affects the temperature of conduits exposed to sun is the color of the surface on which they are installed. Light-colored roofs reflect heat onto conduits raised more than a few inches above the surface of the roof. Conduits on dark-colored roofs experience less extreme temperatures.

Effect of Height

• The height at which a wiring system is installed has a major effect on the temperature of the conduit. In general, the closer the system is to the roof’s surface, the warmer it will be. The interior of a conduit placed a foot above the roof’s surface in direct sunlight has been found to experience a drop in heating differential of as much as 40 degrees.

Other Factors

• Elements such as the texture of the roof, the material used in the conduit, the time of year and the climate are considered likely to affect temperature and performance. These factors have not been fully researched.