NEC 2026 Article 726: Class 4 Fault-Managed Power Systems Complete Guide

Class 4 Fault-Managed Power Systems (FMPS) represent the first new power classification in the NEC in 45 years. Article 726 governs these innovative systems that deliver high power with low-voltage safety characteristics. Here's what contractors need to know.

Quick Answer

Article 726 covers Class 4 Fault-Managed Power Systems—technology that delivers up to 450V and 2,000W safely over distances up to a mile using low-voltage wiring methods. The key innovation is active monitoring: if a fault is detected, power shuts off within milliseconds, making the system safer than traditional high-voltage power distribution despite operating at higher voltages.

What Is Class 4 Fault-Managed Power?

Fault-Managed Power (FMP) is defined in NEC Article 100 as:

"A powering system that monitors for faults and controls current delivered to ensure fault energy is limited."

Unlike Class 2 and Class 3 systems that are power-limited at the source, Class 4 systems achieve safety through active monitoring and control. The system continuously checks the circuit, and if any fault condition is detected—a short, exposed conductor, or other anomaly—power transmission stops within milliseconds.

Multiple Names, Same Technology

In the industry, you may hear Class 4 power called by different names:

Fault-Managed Power Systems (FMPS) – NEC terminology
Digital Electricity™ – VoltServer trademark
Packet Energy Transfer (PET) – Technical description
Pulsed Power – General industry term
Smart Transfer Systems – Marketing terminology

These all refer to systems covered by Article 726 when properly listed and installed.

How Class 4 Power Works

Class 4 systems transmit electricity in discrete packets—up to 500 per second. Each packet includes a safety check before transmission:

Check: The transmitter verifies the line is safe
Transmit: If safe, a power packet is sent
Verify: The receiver confirms receipt
Repeat: Process continues hundreds of times per second

If any check fails—the line is cut, someone touches a conductor, water intrusion occurs—transmission halts within milliseconds. The fault energy is so limited that fire initiation and electric shock risks are mitigated even at high voltages.

System Components

A Class 4 system consists of three main components (per 726.2):

Component	Function	Requirements
Class 4 Transmitter	Converts AC power to controlled packets	Listed per UL 1400-1
Class 4 Cabling System	Carries power packets to receivers	Listed per UL 1400-2
Class 4 Receiver	Converts packets back to usable power	Listed per UL 1400-1

Critical: Transmitters and receivers must be manufactured by the same company and listed together as a system. You cannot mix components from different manufacturers.

Class 4 vs. Power over Ethernet (PoE)

Many low voltage contractors are familiar with PoE for powering devices like IP cameras and access points. Class 4 is designed to extend similar concepts to higher power applications:

Specification	PoE Type 4 (Class 2)	Class 4 FMPS
Maximum Voltage	60V DC	450V DC/AC peak
Maximum Power	90W	2,000W (at 100m)
Maximum Distance	100m (328 ft)	1 mile+ (at lower power)
Safety Method	Power limited at source	Fault-managed (active monitoring)
Cable Type	Cat5e/Cat6 Ethernet	Class 4 listed cable (UL 1400-2)
NEC Article	Article 725 (Class 2)	Article 726
Dwelling Use	Permitted	Not permitted

Why Class 4 Matters for Low Voltage Contractors

Class 4 power opens new opportunities:

Backbone Power: Power PoE switches remotely without electrical runs
Long Runs: Deliver power to cameras, access points, and displays at distances impossible with PoE
Smart Buildings: Centralized power distribution for IoT devices
Stadiums/Arenas: Power distributed displays and digital signage
Outdoor Applications: LED lighting, surveillance in parking lots and campuses

NEC 2026 Article 726 Structure

Under NEC 2026's reorganization, Article 726 integrates with the new limited-energy framework:

Article Structure

Part I: General – Scope, definitions, applications
Part II: Circuits Extending Beyond One Building – Outdoor installations
Part III: Separation Requirements – 726.136 separation from other circuits
Part IV: Listing Requirements – UL certification mandates

Key Code References

Under NEC 2026, Class 4 systems reference several interrelated articles:

Article	Topic	Relevance to Class 4
720	General Requirements for Limited-Energy	Foundation for all limited-energy including Class 4
721.50	Power Sources	Class 4 transmitter requirements
722.150	Class 4 Cable	Cable selection and marking
726	Class 4 FMPS Systems	Primary article for Class 4 installation
750	Limited-Energy Grounding and Bonding	Class 4 grounding requirements

Listing and Certification Requirements

Class 4 systems have strict listing requirements. This is not optional:

UL 1400-1: Systems (Transmitters and Receivers)

All Class 4 transmitters and receivers must be listed to UL 1400-1, "Outline for Fault-Managed Power Distribution Technologies — Part 1: General Requirements."

Key UL 1400-1 requirements:

Transmitter and receiver must be from the same manufacturer
System must be listed as a complete system, not individual components
Maximum voltage and current output must be durably marked and plainly visible
Fault detection must halt power within specified time limits

UL 1400-2: Cable

Class 4 cable must be listed to UL 1400-2, "Outline for Fault-Managed Power Distribution Technologies — Part 2: Cable."

Important notes about cable:

Class 4 cable is a specific category—not repurposed Ethernet or speaker wire
Excessive cable length increases capacitance, which can affect fault-management safety
Cable must be marked with Class 4 designation
Typically 18AWG, 4-pair construction for Digital Electricity systems

What Happens Without Proper Listing?

If a system or cable is not UL 1400 listed:

It is NOT a Class 4 system under the NEC
Article 726 does NOT apply
The installation may require conduit, grounding, and separation as a higher-class circuit
AHJ can reject the installation

Installation Advantages

The safety characteristics of Class 4 enable simplified installation compared to traditional high-voltage power:

No Conduit Required (Most Situations)

Article 726 permits installation without conduit in most applications. This provides:

Faster installation
Lower material costs
Better move/add/change flexibility
Reduced labor for pulls

Simplified Separation Rules

Because Class 4 is fault-managed, it can share pathways with other limited-energy systems:

May be installed in the same cable, enclosure, or raceway as Class 2 circuits
May be installed alongside PoE and Ethernet data circuits
Section 726.136 provides specific separation requirements from higher-voltage circuits

Section 726.136 Separation Requirements

Class 4 circuits require separation from:

Electric light and power circuits
Class 1 circuits
Non-power-limited fire alarm circuits
Medium-power network-powered broadband communications cables

Specific requirements apply in manholes, raceways, and cable trays per 726.136 subsections.

Where Class 4 Is NOT Permitted

Dwelling Units Excluded

Class 4 systems are NOT permitted in dwelling units. This includes:

Single-family homes
Apartments
Condominiums
Dormitory rooms
Hotel guest rooms

The exclusion relates to NEC 210.6 voltage limitations for dwelling units. Class 4's potential 450V operation exceeds dwelling unit voltage limits.

Common Class 4 Applications

Where Class 4 IS commonly used:

Commercial Office Buildings: Powering distributed PoE switches, lighting, access control
Stadiums and Arenas: LED displays, digital signage, distributed cameras
Airports and Transit: Information displays, public announcement systems
Warehouses: Long-run LED lighting, camera systems
Campus Environments: Outdoor lighting, parking lot surveillance
Indoor Agriculture: LED grow lights with centralized power management
Cell Tower Sites: Remote radio units, small cells

Practical Considerations for Contractors

Training Requirements

Before installing Class 4 systems:

Obtain manufacturer-specific training (most Class 4 vendors require certification)
Understand the specific system you're installing (Digital Electricity, Panduit FMP, etc.)
Know UL 1400 listing requirements for your jurisdiction's AHJ

Licensing Considerations

Licensing requirements for Class 4 vary by state:

Some states may consider Class 4 work within low voltage/limited energy license scope
Other states may require electrical contractor licensing due to voltage levels
Check with your state licensing board before bidding Class 4 projects

The "98V RMS" limit in some state limited-energy licenses creates ambiguity since Class 4 can operate well above 98V. Consult your AHJ.

Commissioning and Testing

Class 4 systems require proper commissioning:

Verify transmitter-receiver pairing matches manufacturer specifications
Test fault-management response before energizing
Document cable lengths (excessive length affects capacitance and safety)
Verify marking and labeling requirements per 726.x

Connector Requirements

Per Article 726:

Connectors for Class 4 circuits shall NOT be interchangeable with non-power-limited sources on the same premises
Junctions and mating connectors must guard against inadvertent contact with live parts
Use only manufacturer-specified connectors for the system being installed

NEC 2026 Updates to Class 4

NEC 2026 integrates Class 4 into the new limited-energy framework:

Article 720 Foundation: Class 4 now follows the general requirements in Article 720 alongside other limited-energy systems
Cross-References: 721.50, 722.150 provide coordinated requirements for Class 4 power sources and cables
Unified Grounding: Article 750 provides grounding requirements applicable to Class 4 along with other limited-energy systems

The fundamental Class 4 technology and safety requirements remain similar to NEC 2023, but the organizational structure provides clearer navigation through related requirements.

Inspection Considerations

When preparing for inspection of Class 4 installations:

Have UL Listings Available: Inspector may request documentation showing UL 1400-1 and UL 1400-2 compliance
Verify System Match: Transmitter and receiver must be from same manufacturer
Check Labeling: Maximum voltage and current should be marked and visible
Document Separation: Show compliance with 726.136 where Class 4 runs near other circuits
Confirm Non-Dwelling Use: Be prepared to confirm the space is not a dwelling unit

Future of Class 4 Power

Industry trends suggest Class 4 adoption will accelerate:

Smart Building Growth: IoT devices and distributed power needs favor Class 4 architecture
PoE Backbone: Class 4 as the power backbone for PoE switches becomes more common
ESG and Efficiency: DC power distribution reduces conversion losses
Manufacturer Investment: VoltServer, Panduit, Cisco, and others are investing in Class 4 solutions

Low voltage contractors who develop Class 4 expertise now will be well-positioned for this growing market segment.

Key Takeaways

Topic	Key Points
What Is Class 4?	Fault-managed power using active monitoring, up to 450V and 2,000W
How It Works	Power transmitted in packets with continuous safety checks
Listing Required	UL 1400-1 (systems), UL 1400-2 (cable) mandatory
Installation Benefits	No conduit required, simplified separation, faster installs
Where NOT Allowed	Dwelling units are excluded
Key Applications	Commercial buildings, stadiums, campuses, warehouses
Licensing	Check state requirements—voltage may affect license scope
NEC 2026 Integration	Now part of Chapter 7 limited-energy framework with Article 720 foundation

Find Projects Using Class 4 Power

Class 4 installations are growing in commercial, stadium, and campus projects across the country. Stay ahead of these opportunities.

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Last updated: February 2026. This article provides general guidance on NEC 2026 Article 726. Always verify current code requirements with the official NEC and your local AHJ. Class 4 system installation may require manufacturer certification and specific licensing depending on your jurisdiction.