The 2029 NEC Is Expanding Coverage for Medium Voltage and DC Distribution

A 15kV switchgear lineup in an industrial plant. A DC microgrid in a data center. A battery energy storage system feeding a campus distribution network. These installations are increasingly common, and the NEC is catching up.

The NEC Correlating Committee has reconstituted two task groups for the 2029 code cycle: a Medium Voltage Task Group with a dedicated Code-Making Panel (CMP-9), and a DC Distribution Task Group focused on DC power systems. Both are developing public inputs to expand NEC coverage for systems that were historically handled by IEEE, NESC, or left to engineering judgment.

Medium Voltage Gets Dedicated Coverage

The NEC defines "Voltage, High" as systems over 1000V AC or 1500V DC nominal — the threshold that triggers separate equipment and installation requirements. The industry commonly calls the range from 1kV to 52kV "medium voltage," and the NEC includes this as an informational note. Either way, these systems have always been something of an afterthought in the code. Article 490 (later 495) covered equipment over 1000V, but requirements were thin compared to the detailed rules for 600V-class systems. Engineers designing 4.16kV or 13.8kV systems relied heavily on IEEE standards (C37 series for switchgear, the 3000-series collection that replaced the legacy Color Books) because the NEC didn't address the specifics.

That's changing. The Medium Voltage Task Group is reviewing all requirements for medium voltage systems and developing public inputs to:

• Reorganize requirements for motors, motor circuits, and controllers rated over 1000 VAC, 1500 VDC into a consolidated article
• Separate medium voltage equipment requirements from low voltage articles so they stand on their own
• Develop grounding requirements specific to medium voltage systems (an MV Grounding Sub Task Group is working on Article 350 requirements)

In the proposed 2029 structure, Chapter 17 is dedicated entirely to Equipment Over 1000 VAC, 1500 VDC. This chapter includes new articles for medium voltage switchgear (Article 1702), mobile and portable equipment (Article 1704), boilers (Article 1706), equipment with insulating liquids (Article 1708), and equipment vaults (Article 1710). CMP-9 has dedicated responsibility for these articles.

This matters for engineers who design or analyze medium voltage distribution systems. Having dedicated NEC articles means more specific, enforceable installation requirements — and more detailed code references for specifications and study reports. It also means inspectors will have clearer guidance for medium voltage installations, which historically relied on the broad strokes of Article 490.

DC Distribution Enters the Code

The DC Task Group has been reconstituted to review requirements for DC distribution and develop public inputs. This reflects a reality that the industry has been living for years: DC distribution is no longer limited to battery rooms and telecom power plants.

Data centers are deploying 380V DC distribution to eliminate AC-DC conversion losses. Microgrids combine solar PV, battery storage, and DC loads on common DC buses. EV charging infrastructure operates at DC voltages up to 1000V. The NEC needs requirements that address these systems — not as special cases, but as standard installation methods.

The current NEC addresses DC in scattered locations: Article 690 for PV, Article 706 for energy storage, Article 480 for batteries, and various sections in Chapter 2 for general DC wiring. The DC Task Group's mandate is to consolidate and expand DC distribution requirements so engineers have a coherent set of rules for DC power systems.

Key areas being addressed include:

• DC distribution bus configurations and protection
• DC grounding and bonding requirements (which differ significantly from AC systems)
• Conductor sizing and protection for DC circuits
• Integration with AC systems at the point of interconnection
• Requirements for DC disconnecting means and switching

What This Means for Power System Engineers

If you do short circuit studies or coordination studies on medium voltage systems, dedicated NEC articles give you more specific requirements to reference. Equipment ratings, installation clearances, and protection requirements that were previously covered in broad strokes will have more detailed rules.

For DC systems, the expansion means that cable sizing and fault current calculations for DC circuits will have clearer NEC grounding (pun intended). Currently, engineers often default to IEEE or manufacturer guidance for DC-specific design decisions because the NEC doesn't address them. Consolidated DC requirements change that calculation.

Both developments also affect how power system analysis software needs to handle these systems. As NEC requirements for medium voltage and DC become more detailed, engineering tools need to check compliance against these new rules. At ekx, we're tracking these changes to ensure our analysis tools stay current with the evolving code.

Timeline

The Public Input period for the 2029 NEC closes April 9, 2026. Both task groups are developing public inputs for submission before this deadline. The First Draft Meetings are scheduled for fall 2026, where the code-making panels will review all submitted inputs.

Engineers working on medium voltage or DC distribution projects should consider submitting public inputs based on their field experience. The code benefits most when practicing engineers contribute real-world installation challenges that the task groups may not have considered.

Key Takeaways

• The proposed 2029 NEC creates Chapter 17 dedicated entirely to equipment over 1000 VAC, 1500 VDC
• CMP-9 has dedicated responsibility for these articles, including a grounding sub task group
• The DC Task Group is developing consolidated requirements for DC distribution systems
• Both reflect the industry shift toward DC microgrids, battery storage, and medium voltage industrial systems
• Public Input closes April 9, 2026 — engineers with field experience should consider contributing