The 2014 NEC®, Section 406.9 (B) (1) now requires these covers to be listed and identified as "Extra Duty." The "Extra-Duty" covers are evaluated to more demanding test requirements than a standard cover. Previously, the requirement for "Extra-Duty" covers only applied to enclosures supported by grade, not one- and two-family dwellings. There was concern that covers were being damaged in residential and commercial installations.