External Influences Classification Code (AA, AB, AD, ...)

A standardised classification code, adopted from IEC 60364-5-51, used to systematically record the environmental conditions at the location of an electrical installation, built up from a capital letter for the category (A = environment, B = utilisation, C = construction of buildings), a second letter for the specific influence within that category, and a digit for the intensity class; for example AA denotes ambient temperature (AA1 to AA8, from very cold to very hot), AB denotes atmospheric humidity, AD denotes the presence of water (AD1 = negligible up to AD8 = submersion), and AG denotes mechanical impact. Based on this coding, recorded in a table per room or part of the installation, the designer determines which degree of protection (IP rating), material choice and installation method are required — a bathroom with an AD class and increased humidity, for example, requires a higher IP classification than a dry office space. The classification code thus forms the systematic link between the actual physical conditions on site and the concrete requirements NEN 1010 places on equipment and method of installation, and is recorded in the handover file so that future modifications to the installation can be assessed against the same starting assumptions.