3.) The non-use of expansion fittings in Rigid Non-Metallic (PVC) conduits that are subject to thermal expansion and contraction.
Sections 300.7(B) and 352.44 require the use of an expansion fitting in exposed straight runs between securely mounted items such as boxes, conduit bodies and elbows of non-metallic raceways that are subject to large temperature variations. The expansion fitting is required when the length change, in accordance with Table 352.44(A) is 0.25" or greater.
Example: in a 100' run of Rigid Non-Metallic Conduit, that is exposed to a 100 degree difference in temperature, the computed expansion is 4.1". With a 100 degree difference of temperature and in an area not exposed to direct sunlight the length change in a 6' 1" section of Non-Metallic conduit will be more than 0.25".