Underwriters Laboratories announce an important alteration to the UL508A standard

The UL 508A standard certifies that the assembly of all electric panel components (size and design testing) conforms to US standards as mandated by the National Electric Code (NEC), the chief regulatory benchmark source for the American system. The NEC is revised every three years: between 2005 and 2006 new electric panel guidelines were issued.



Each part of the standard, which came into force in April 2006, lays out the benchmarks for working out short-circuit current calculation of electric panels with particular attention to the solutions for elevating that value (the use of F type combination motor controllers and current limiting fuse wires or circuit breakers). UL is the only agency recognised by NEC which has a valid system for calculating short-circuit current.



Another important change regarding componentry is that it is in fact necessary that electromagnetic filters are presently equipped with short-circuit current calculation. Other fundamental changes regard cable dimensioning for internal wiring: the absorption table for cables has new values. There has already been a change to the standards on interlock types permitted and their requirements relative to internal movement of the general switch.



The last updates were issued at the end of 2006 and the new requirements came into force in March 2007. Throughout the year, Underwriters Laboratories are organising training days in order to make the new directions known, and the results from the update to the rules and their impact on the way electric panels are designed and manufactured, in conformity with the UL 508A standard.