Distance from main power distribution box to sub-distribution box

There is no specific NEC-mandated distance between a main panel and a subpanel, but practical installation depends on wire size, conduit fill, and accessibility requirements.Electrical Code and Practical ConsiderationsThe National Electrical Code (NEC) does not specify a minimum or maximum distance between a main distribution panel and a sub-distribution panel. Instead, the focus is on safety, accessibility, and proper conductor installation. Key considerations include:Working Space and Clearance: NEC 110.26 requires a minimum clearance of 30 inches wide, 36 inches deep, and 6.5 feet high in front of panels to allow safe access and operation .Conductor Size and Bend Radius: For conductors #4 AWG and larger, the distance between raceways or pull boxes must allow for proper bending without damaging insulation. Typically, the spacing is 6 to 8 times the conduit diameter for angle pulls .Pull Boxes: If the distance is long or the wire size is large, a pull box may be required to facilitate installation and prevent conductor damage. NEC Article 314.28 covers sizing requirements for junction and pull boxes .Practical Installation GuidelinesResidential Systems: Subpanels are often installed within the same building, typically 10–50 feet from the main panel, depending on layout and load distribution. The distance is usually determined by convenience, cable routing, and minimizing voltage drop.Commercial or Industrial Systems: Subpanels may be located further away, sometimes hundreds of feet, but this requires careful consideration of voltage drop, conductor sizing, and protective devices .Conduit and Cable Routing: Ensure that conduits are properly sized for the conductors and that bends comply with minimum bend radius rules. For example, a 1.5-inch EMT conduit requires at least 9 inches spacing for angle pulls .SummaryWhile there is no fixed distance requirement, the main factors influencing the placement of a subpanel relative to the main panel are:Accessibility and working space (NEC 110.26)Conductor size and bend radius (NEC 314.28)Voltage drop considerations for long runsEase of installation and maintenance In practice, subpanels are installed as close as practical to the main panel while meeting these safety and installation requirements. For long distances, consider using pull boxes or larger conduits to facilitate wiring.