The PVC conduit size shall be bigger than 1/2 inch and small than 6 inch, the sizes not within this ranges shall not be used. Fill Limit Calculation: Fill limit are calculated using the cross-sectional area of conductors and the size of the conduit. Proper conduit fill is critical for electrical safety, code compliance, and system performance. Published by the National Fire Protection Association (NFPA), the NEC is widely adopted and enforced at the federal, state, and. Meeting NEC Article 300. 5 requirements for underground electrical conduit installations isn't just about passing inspection—it's about ensuring decades of safe, reliable service. The 2023 National Electrical Code establishes minimum burial depths based on wiring method, voltage level, and location. Do you know the rules for installing the four types of metal conduit listed in the NEC? Fig. Rigid metal conduit requirements can be found in NEC Art.