OSHA and the National Electrical Code (NEC) specify the minimum clearance distances required around electrical panels. These include a depth of 36 inches, a width of 30 inches, and a height of 78 inches. Distribution box and switch box should not exceed 30 meters. Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers. At this. What do the primary, secondary, and tertiary boxes of a distribution box mean? This is a relative issue. From the transformer's low-voltage side (0.
