What it is
EC&M article explains NEC Article 300 general requirements that apply to all Chapter 3 wiring methods. Covers 2014 code changes including expanded underground installation rules, new allowances for RTRC conduit in damage-prone areas, and clarifications on conductor grouping and protection requirements.
Why it matters
Electrical contractors and MEP designers must understand Article 300 before applying specific wiring methods in Articles 320+. The 2014 cycle expanded underground rules to explicitly cover conductors (not just cables) beneath buildings and added RTRC-XW as an approved raceway for physical damage locations alongside RMC/IMC/Sch80 PVC, affecting material choices and install costs for feeders and branch circuits in retrofit and new construction.
Evidence from source:
- 2014 NEC expanded rules for cables beneath buildings to include conductors beneath buildings [300.5(C)]
- All conductors of same circuit must run in same raceway [300.3(B)] including ungrounded, grounded, EGC, and bonding conductors
- If direct-buried cables/raceways subject to physical damage, must use RMC, IMC, RTRC-XW, or Schedule 80 PVC per 300.5(D)(4)
Links
- Canonical source: https://www.ecmweb.com/national-electrical-code/code-basics/article/20899204/branch-circuit-feeder-and-service-wiring-methods
- Topic: /topics/code-standards/
- Topic: /topics/pathways-install/
Open questions
- How does the RTRC-XW cost/labor profile compare to Schedule 80 PVC for underground feeder runs subject to physical damage?
- What AHJ interpretation issues have emerged around the expanded 300.5(C) language for conductors vs. cables beneath buildings?