Whew! That Was a Close Call
A mere ½ in. closer, and this screw could have done some serious damage to the EMT and the conductors inside. This is a great example of why Sec. 300.4(E) requires raceways, cables, and boxes to be installed and supported to provide no less than 1½ in. of separation between the lowest surface of the metal-corrugated sheet roof decking and the top of the raceway cable or box. Screws such as the one in the picture are often used to hold down insulating materials when repairs are made to rubber membrane roofs. The workers making the roofing repairs have no way of knowing if the screw they are installing will be catching the high part or low part of the metal corrugated roof, so they use very long screws in order to guarantee that the screws will grab something. If raceways or cables are installed too close to the metal roof decking, they can be damaged by these long screws. I have gotten many service calls to make repairs to cables and raceways damaged during these types of roofing repairs. Securing cables and raceways directly to the metal roof deck was a very common practice until the Code finally prohibited it in 2002.
A Not-So-Liquidtight Installation
I will certainly give this installer credit for installing the Class 2 control wires in a raceway separate from the power wires feeding this air-conditioning equipment. Section 725.136 generally requires Class 2 and Class 3 circuits to be kept separated from power conductors and provides several methods to achieve this separation. However, the choice to install liquidtight flexible nonmetallic conduit (LFNC) in this outdoor, sun-drenched area may need to be reviewed. Section 300.6(C)(1) requires nonmetallic raceways exposed to direct sunlight to be listed or identified as being sunlight resistant. Section 356.10(3) does permit LFNC to be installed in outdoor locations if the LFNC is listed and marked for this purpose. According to the product standards, LFNC suitable for installation outdoors is marked “outdoor.” The LFNC in this photo has been so damaged by the sunlight that I could not read any of the markings on it. In fact, the LFNC was so dry and brittle that it had cracked and completely separated. Perhaps this LFNC was not suitable for this outdoor location. Sunlight combined with extreme cold in the winter and extreme heat in the summer has taken a severe toll on this raceway, and it needs to be replaced.
