Illustrated Catastrophes: Mother Nature Takes Her Toll…Again.

All references are based on the 2020 edition of the NEC.

The amazing power of thermal expansion and contraction has taken a toll on this installation. The PVC conduit body has been broken into two pieces due to the lack of an expansion fitting being installed on this PVC conduit run. The conductors inside the raceway are now visible and exposed to the elements. Damage from exposure to sunlight, rain, snow, and ice could spell real trouble for these conductors. For PVC conduit installed where the length change is expected to be ¼ inch or more in straight runs between securely installed boxes, cabinets, elbows, or other conduit terminations, Sec. 352.44 requires expansion fittings to be used to compensate for this thermal expansion and contraction. During the course of my 37-year career as an electrician, I have seen many PVC conduit runs, cracked, snapped, twisted, sagged, warped, and otherwise damaged or destroyed by the destructive forces of thermal expansion and contraction. Furthermore, this problem is not limited to exterior installations. Installations in unheated interior locations such as garages, barns, sheds, and other accessory buildings can experience huge temperature swings from summer to winter. Temperature swings in unconditioned attic or loft locations can be even greater than those on the outside of the building!

Most of the sites in the campground were wired in a fashion similar to this one. The installers simply strung UF cables through the trees in order to provide power to the receptacles and lights on the picnic table canopy in each site. This was not for temporary purposes either — this was how it was permanently wired! Section 340.10(3) permits the use of UF cable in wet locations, but Sec. 340.12(11) prohibits UF cable from being used as overhead cable unless installed in accordance with the requirements of Art. 396 for messenger-supported wiring. There were no messenger supports used anywhere in this campground. The UF cables installed here were simply wrapped around tree limbs and branches as a means of support. In some cases, I noticed the UF cables were even tied into knots in order to keep them snugged tightly against the trees! If messenger supports were used, this type of installation would still be a violation of Sec. 225.26, which prohibits trees and other vegetation from being used for support of overhead conductors of outside branch circuits or feeders. I think a complete “do over” is needed for the wiring in this campground!