The impact of the 1996 National Electrical Code on total control system design

The extensive revisions to Article 725 (“Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits”) in the 1996 Edition of the National Electrical Code have a large effect on the design and installation of the typical remote control and signaling circuits often used by transit and transportation facilities. This has become very important with the increased use of microprocessor based control devices, where serious operational problems can occur when different classes of control conductors are combined within the same cable raceway or bundle, or are even internal to the same piece of equipment. Increased continuous attention from both the end user´s project electrical engineer and the equipment manufacturer´s design electrical engineer is required. These two items (the microprocessor and the NEC Article 725), when neglected on a specific power equipment project, will have a severe negative total impact for an economically and electrically successful completion of the end project