Class 4 Power & NEC Article 726: What It Means for Your Build

NEC Article 726 formalizes Fault-Managed Power as a distinct circuit class, and understanding what it demands—and what it relaxes—can reshape how you plan your next infrastructure project.
By Todd Taskerud, AWS CCP, RCDD/NTS/OSP/WD, LEED GA
5 min read
Class 4 Power & NEC Article 726: What It Means for Your Build

A New Circuit Class Changes the Conversation

If you have been following the 2023 National Electrical Code (NEC/NFPA 70), you already know that Article 726 introduced something genuinely new to the codebook: a formal definition and regulatory framework for Fault-Managed Power (FMP), sometimes called Class 4 power. For infrastructure designers, contractors, and end-users, this is not a minor editorial update. It redraws the line between what is an electrical installation and what is, functionally, a cabled power-delivery system that behaves more like structured cabling than a traditional power circuit.

In this article I want to walk through what Article 726 actually establishes, how it differs from the existing Class 1, 2, and 3 circuit framework in Article 725, and what the practical implications are when you are planning a build—whether that is a commercial campus, a remote industrial site, or a data-center edge deployment.

What Article 726 Actually Says

NEC Article 726 defines Class 4 as a fault-managed power system: one in which the source continuously monitors the energy it delivers and can interrupt that delivery in milliseconds upon detection of a fault condition. That near-instantaneous shutoff is what makes the system touch-safe despite operating at voltages well above the Class 2 and Class 3 thresholds defined in Article 725.

The code requires that FMP equipment be listed to UL 1400-1 (the standard for fault-managed power systems and equipment) and that cable used in these systems be listed to UL 1400-2 (the cable standard). These are not optional listings—they are the compliance gateway for Article 726 installations.

One of the most consequential relaxations Article 726 provides is in wiring methods. Because the system is inherently monitored and self-limiting at the source, Article 726 permits installation without conduit in most cases, similar to the wiring-method flexibility already familiar to low-voltage installers working under Article 725. For project budgets and schedule, that is a meaningful difference from a conventional branch-circuit power run.

How Class 4 Differs from Class 1, 2, and 3

Article 725 has governed remote-control, signaling, and power-limited circuits for decades. Its Class 2 and Class 3 limits are based on inherent current limiting—the source simply cannot deliver enough energy to be hazardous under normal conditions. Class 4 takes a different approach: the voltage and power levels can be substantially higher, but hazard mitigation is achieved through active, continuous monitoring rather than inherent limitation.

  • Class 2/3 (Article 725): Safety through source power limitation; lower voltage/power envelopes; no active fault detection required.
  • Class 4 (Article 726): Safety through fault-managed, packet-based energy delivery; millisecond shutoff on fault detection; higher voltage and power delivery possible; UL 1400-1/-2 listing required.

The underlying technology behind most commercial Class 4 deployments uses what is variously called Digital Electricity (DE)—a trademark of VoltServer, a Heather Technologies partner—Packet Energy Transfer, or simply pulsed power. Energy is delivered in discrete, monitored packets; if any packet does not return the expected signature, the source halts delivery before a hazardous condition can develop at the conductor.

Real-World Capabilities and What to Flag

VoltServer's DE platform, as represented in publicly available partner documentation, is described as capable of delivering power over extended distances on data-type cable—representative figures cited by VoltServer include up to approximately 450 V and approximately 2,000 W per channel over distances approaching 2 km (roughly 1 mile). These figures should be independently verified against current VoltServer product documentation before use in any design or specification. Distance and power figures vary by cable type, gauge, and installation conditions, and product capabilities evolve with firmware and hardware generations.

DCPacket, another Heather Technologies partner whose Titan Platform targets data-center FMP deployments, operates in conjunction with VoltServer technology (relationship formalized in a December 2025 partnership announcement). Specific Titan Platform power and distance specifications should be verified directly with DCPacket prior to design.

What This Means for Your Build

Cabling and Pathways

Because Article 726 allows no-conduit installation in most cases, your pathways and spaces planning under ANSI/TIA-569 can treat FMP cable runs more like low-voltage signal cabling than like branch-circuit power. This has real implications for tray fill, sleeve sizing, and firestop coordination. You still need to coordinate with your AHJ (authority having jurisdiction), because local amendments to the NEC can and do modify what Article 726 permits in a given jurisdiction. Not all states or municipalities have adopted the 2023 NEC on the same timeline.

Plenum and Riser Ratings

Even with relaxed wiring methods, NEC Chapter 3 and Article 726 still require appropriate cable ratings for the environment. Plenum spaces require CMP-rated cable; riser shafts require CMR-rated cable at minimum. UL 1400-2 listed cables carry their own environmental ratings, but you must confirm that the listed cable you specify also carries the CMP or CMR marking appropriate to your installation path.

Grounding and Bonding

FMP systems are not exempt from grounding and bonding requirements. Your telecommunications bonding infrastructure—TMGB, TGB, and the backbone bonding conductors described in ANSI/TIA-607—should be evaluated in the context of any Class 4 deployment, particularly in data-center or campus environments where multiple systems share common pathways. Consult your electrical engineer of record early.

Labeling and Administration

Class 4 circuits should be clearly identified in your administration documentation per ANSI/TIA-606. Mixing FMP and conventional low-voltage signal cabling in the same pathway is not automatically prohibited, but it demands clear labeling to prevent maintenance errors downstream.

The Opportunity Article 726 Creates

Fault-Managed Power addresses a real gap in the infrastructure toolkit. Traditional PoE under IEEE 802.3bt (Type 3 and Type 4, up to 60 W and 90 W at the PSE respectively, over structured copper cabling governed by ANSI/TIA-568.2-D) is excellent for edge devices within structured-cabling reach. But there are applications—remote surveillance nodes, distributed antenna systems, industrial sensors, edge compute in buildings without local panel capacity—where you need more power over longer distances than PoE can deliver, without the cost and disruption of running conduit and pulling branch-circuit wire.

Article 726 gives the code framework that makes Class 4 a legitimate, inspectable, insurable solution. That is the shift worth paying attention to as you plan your next build.

About the author — Todd Taskerud, AWS CCP, RCDD/NTS/OSP/WD, LEED GA, is a BICSI-credentialed communications distribution designer at Heather Technologies, specializing in fiber, copper, and data-center network infrastructure.