Article 320 is now Article 360. So is everything else.
Every article number in Chapter 3 changed in the 2027 edition. If your LOTO procedures, safety program, training materials or battery room signage cite a Chapter 3 article by its old number, they are now pointing at the wrong article — and in two cases, at a completely different subject.
Battery rooms moved from Article 320 to Article 360. Capacitors moved the other way — from 360 to 320. A procedure that says "per Article 320" and means batteries now cites the capacitor article.
§ Old to new
| 2024 edition | 2027 edition | Topic | Change |
|---|---|---|---|
| — | 310 | DC electrical hazards | NEW Unified DC thresholds |
| 360 | 320 | Capacitors | Renumbered + clarified |
| 340 | 330 | Power electronic equipment | Renumbered |
| 330 | 340 | Lasers | Renumbered [verify] |
| 310 | 350 | Electrolytic cells | Renumbered |
| 320 | 360 | Batteries and battery rooms | Renumbered + major technical revision |
| 350 | 370 | Research and development laboratories | Renumbered |
| — | 380 | Electrical double layer capacitors (supercapacitors) | NEW With Annex T |
| — | 390 | Photovoltaic (solar PV) systems | NEW |
§ Why the committee did it
The technical committee's stated reasoning was that Chapter 3 had "evolved using a patchwork of subjects generally developed in isolation" from each other and from the rest of the standard. The reorganization harmonizes common methods across the special-equipment articles, complies with the NEC Style Manual, removes redundancy, and leaves room for future additions.
The renumbering itself was described as editorial — existing technical requirements were not changed by the move. Three genuinely new articles came with it, and Article 360 was substantially rewritten on its own merits.
§ The three new articles
DC electrical hazards. Baseline DC thresholds and guidance that apply across multiple Chapter 3 equipment types before the specific articles add their own requirements. Consistent with the battery and PV thresholds.
Electrical double layer capacitors. Supercapacitors — energy storage that behaves like a capacitor at battery-scale capacitance. Applies above 100 V DC nominal or 1,000 W theoretical maximum power. They present shock, thermal and arc flash hazards but eliminate the arc blast pressure wave that conventional capacitors carry. Requires a written discharge procedure using an appropriately sized resistor, and treats any uninstalled EDLC without a shorting conductor as fully charged. The hidden hazard is residual charge rebuild — an EDLC can regain voltage after discharge with no external circuit.
Photovoltaic systems. A PV array is energized whenever sunlight reaches it; opening the inverter AC disconnect does not de-energize the DC conductors. Requires a risk assessment before every energized PV task, written procedures for connector manipulation (including the wrong-connection short circuit scenario), and no work above the thresholds without an ESWC or documented energized work procedures. Thresholds: contact thermal above 1,000 W, shock above 100 V and 40 mA, arc flash above 150 V and 1.2 cal/cm².
All three land in a modern data center. Article 360 covers every UPS battery room and BESS installation. Article 330 covers the UPS, rectifiers and VFDs themselves. Article 380 covers supercapacitor ride-through systems, which are increasingly specified as an alternative to short-duration battery strings. Article 390 covers rooftop and ground-mount PV on campuses that have added on-site generation.
§ What to update, in order
Battery room LOTO procedures — old 320, new 360. Highest volume of affected documents.
Battery room signage — while you are there, Article 360 also now requires a thermal hazard warning. See the sign requirements →
Capacitor safety procedures — old 360, new 320. These two swapped, which is the most confusing possible outcome.
Laboratory and test-cell programs — old 350, new 370.
Electrolytic cell procedures — old 310, new 350.
Training materials and slide decks — every deck that shows the Chapter 3 map.
Check whether you now have new obligations — if you have PV, supercapacitors or any DC energy storage, Articles 390, 380 and 310 apply to you and did not exist before.
Documents get updated; signage does not. Battery room warning signs are usually printed once at commissioning and never touched again. They now need a thermal hazard warning added regardless of the renumbering.
NFPA 70E 2024 → 2027 transition training
A focused class on exactly what changed and what your organization has to update — including a walkthrough of the Chapter 3 map.
See the schedule Bring it onsite