Introduction
Power distribution in network infrastructure and data-center environments has long relied on two established paradigms: alternating current (AC) distribution from utility feeds stepped down through transformers and panelboards, and direct current (DC) distribution commonly used in telecom central offices and battery-backed power plants. A third approach—Fault-Managed Power (FMP), formally codified as Class 4 in the 2023 National Electrical Code (NEC) under Article 726—has emerged as a viable alternative, particularly for high-density AI compute environments, long-reach edge deployments, and hyperscale data centers seeking to reduce installation complexity and copper weight.
Traditional AC Distribution
Conventional AC distribution delivers power at voltages typically ranging from 120 V to 480 V (single- or three-phase) in North American facilities. Wiring methods must comply with NEC Chapter 3, requiring conductors to be installed in conduit, cable trays, or other approved raceways in most commercial and industrial settings. Branch circuits, panelboards, and overcurrent protective devices are governed by NEC Article 210 and Article 240, respectively. The result is a well-understood, broadly code-compliant system, but one that carries meaningful installation costs: conduit runs, labor-intensive pulls, and substantial copper cross-sections all contribute to both capital expenditure and physical weight in raised-floor environments.
From a safety standpoint, conventional AC voltages above 50 V are not considered touch-safe. A fault condition—whether a short circuit, insulation breakdown, or inadvertent human contact—relies on overcurrent protective devices (fuses, breakers) to clear within a code-specified time. Clearing times, while fast, are not instantaneous and do not eliminate shock hazard during the fault interval. This constraint shapes the entire wiring-method regime of NEC Chapter 3.
Traditional DC Distribution
Telecom-grade DC distribution, historically at –48 V, provides inherent advantages in battery backup integration and reduces conversion stages compared to AC systems that must rectify power at the point of load. Higher-voltage DC buses (240 V DC, 380 V DC) have gained adoption in hyperscale data centers, reducing resistive losses over a given conductor size and improving distribution efficiency. However, high-voltage DC systems still require conduit and wiring methods comparable to their AC counterparts under NEC Chapter 3, and arc-fault behavior in DC circuits presents distinct protective-device challenges relative to AC systems where current naturally crosses zero.
Fault-Managed Power: Class 4 Under NEC Article 726
Governing Standard and Circuit Classification
The 2023 NEC introduced Article 726, establishing Class 4 Fault-Managed Power Systems as a new circuit class. Class 4 stands alongside the existing Class 1, 2, and 3 circuit hierarchy defined in Article 725, but operates on a fundamentally different safety principle. Rather than relying on current-limiting or power-limiting to achieve safety, Class 4 systems use active fault management: the source transmits energy in continuously monitored packets, and upon detection of a fault condition—including short circuit, ground fault, cable break, or human contact—the source interrupts power within milliseconds, achieving a touch-safe result at voltages that would not be touch-safe under conventional distribution methods.
Equipment used in Class 4 systems must be listed to UL 1400-1, and Class 4 cables must be listed to UL 1400-2 (currently an UL Outline of Investigation). This listing framework is what enables the relaxed wiring-method provisions of Article 726: Class 4 cable may in most cases be installed without conduit, a significant departure from the NEC Chapter 3 requirements that govern conventional AC and high-voltage DC wiring.
Technology Implementations
The FMP category encompasses several commercial implementations. VoltServer's Digital Electricity (DE) platform, based on Packet Energy Transfer (PET) technology, is one such implementation. Per VoltServer-published specifications [FLAG], a single transmitter channel supports operation up to approximately 450 V DC and approximately 2,000 W over distances up to approximately one mile (approximately 2 km) on standard data-type cabling; multiple channels may be paralleled to aggregate power capacity [FLAG]. These reach characteristics are notably beyond what conventional branch circuits deliver without voltage drop mitigation, making FMP well-suited to distributed edge nodes, campus wireless infrastructure, and remote data-center equipment.
DCPacket's Titan Platform applies FMP principles to intra-data-center power distribution. As of December 2025, DCPacket and VoltServer announced a partnership to bring combined FMP solutions to hyperscale and AI-dense environments, addressing the challenge of delivering high power densities while reducing installation labor and conduit burden [FLAG: partnership scope and product roadmap details should be verified against current vendor announcements].
Comparative Advantages
The following table summarizes key differences across distribution paradigms:
| Attribute | Traditional AC | High-Voltage DC | Class 4 FMP (NEC Art. 726) |
|---|---|---|---|
| Touch safety mechanism | Overcurrent device clearing | Overcurrent device clearing | Active packet-based fault shutoff (milliseconds) |
| Conduit requirement | Required (NEC Ch. 3) | Required (NEC Ch. 3) | Generally not required (Art. 726 / UL 1400-2 listed cable) |
| Long-reach capability | Limited by voltage drop | Improved over AC | Extended reach on lightweight cabling [FLAG: per vendor specs] |
| Governing NEC article | Art. 210, 240, Ch. 3 | Art. 210, 240, Ch. 3 | Article 726 (2023 NEC) |
| Listed equipment standard | Various UL product standards | Various UL product standards | UL 1400-1 (equipment), UL 1400-2 (cable) |
Installation and Density Implications
For data-center operators and network infrastructure designers, the conduit-free installation pathway permitted under Article 726 translates to measurable reductions in labor hours, structural load, and pathway congestion in overhead trays and underfloor plenums. In AI and hyperscale environments where rack power densities continue to increase, FMP's ability to deliver substantial power over lightweight, listed cable—without the raceway burden of NEC Chapter 3 methods—provides an architectural flexibility that neither traditional AC nor conventional DC distribution readily offers.
Edge deployments present a parallel benefit: remote nodes that are difficult or costly to serve with conventional branch circuits may fall within the extended reach envelope of an FMP transmitter channel, reducing or eliminating the need for intermediate distribution equipment.
Scope Boundary: Protected Distribution Systems
It is worth noting a term that sometimes surfaces alongside power distribution discussions in government and defense contexts: Protected Distribution System (PDS). A PDS is a US government concept governing wireline and fiber telecommunications systems that carry unencrypted classified national security information, defined under CNSSI No. 7003 (2015), which superseded NSTISSI No. 7003 (1996) and is the current governing document of the Committee on National Security Systems. A PDS addresses physical and electromagnetic safeguards on signal-carrying lines—it is not a power distribution standard. Its safety concerns center on deterring and detecting unauthorized physical access to classified communications lines, not on electrical shock or power delivery. These are separate regulatory domains and should not be conflated.
Summary
Class 4 Fault-Managed Power, governed by NEC Article 726 and the UL 1400 series, represents a code-recognized departure from the wiring-method constraints that have historically defined both AC and DC power distribution. Its active fault-detection safety model achieves touch-safe performance at distribution voltages where conventional methods cannot, while the resulting relaxation of conduit requirements creates meaningful installation advantages for data-center, campus, and edge infrastructure. Heather Technologies' partnerships with VoltServer and DCPacket position the company to deliver FMP solutions as adoption of the 2023 NEC and the UL 1400 listing framework continues to expand across the industry.