NEC 2026 Articles 721-723: Class 2 and Class 3 Circuits Complete Guide

If you install security systems, access control, audio/video, or any power-limited circuits, the 2026 NEC has completely reorganized where you find the rules. Article 725 went from several pages to half a page. Here's where everything moved and what it means for your work.

The Big Picture: Why Article 725 Shrank

Open the 2023 NEC to Article 725 and you'll find several pages covering Class 2 and Class 3 power-limited circuits. Open the 2026 NEC to the same article and you'll find less than half a page. What happened?

The answer isn't that Class 2/3 requirements disappeared—they moved. The 2026 NEC reorganizes all limited-energy requirements into a coordinated system of articles. Instead of each article (725, 760, 770, 800, 820, 840) containing its own versions of similar rules, the code now places requirements in dedicated articles based on function:

• Article 720 - General requirements (the "Article 300 equivalent" for limited-energy)
• Article 721 - Power sources for all limited-energy systems
• Article 722 - Cable requirements for all limited-energy systems
• Article 723 - Raceways, cable routing assemblies, and cable trays
• Article 725 - Class 2/3 specific provisions (what's unique to these circuits)
• Article 742 - Overvoltage protection
• Article 750 - Grounding and bonding

This reorganization eliminates the "article-hopping" that frustrated contractors who had to cross-reference multiple articles to find consistent guidance. Now, power source rules are in one place (721), cable rules are in one place (722), and pathway rules are in one place (723)—regardless of whether you're installing Class 2 circuits, fire alarm, or communications.

What Remains in Article 725

The 2026 version of Article 725 contains only three sections:

Section	Title	What It Covers
725.1	Scope	Defines what Article 725 covers: Class 2 and Class 3 power-limited circuits
725.2	Listing and Marking of Equipment for Power and Data Transmission	Requirements specific to power-over-Ethernet and combined power/data equipment
725.127	Wiring Methods on the Supply Side of the Class 2 or Class 3 Power Source	How to wire the line-voltage side feeding your Class 2/3 power supplies

Everything else—cable requirements, installation methods, separation rules, grounding—has moved to the new Chapter 7 articles.

Article 721: Power Sources for Limited-Energy Systems

Article 721 consolidates power source requirements that were previously scattered across Articles 725, 760, and 800. If you need to know what qualifies as a Class 2 or Class 3 power source, this is now where you look.

What Article 721 Covers

• Power source requirements for Class 2, Class 3, and Class 4 circuits
• Listing and marking requirements for power supplies
• Power source interconnection rules
• Voltage and current limitations (referencing Chapter 9 tables)
• Protection requirements

Class 2 vs. Class 3 Power Source Limits

The fundamental distinction between Class 2 and Class 3 circuits lies in their power limitations, which determine both safety characteristics and installation requirements. These limits are specified in Chapter 9, Tables 11(A) for AC and 11(B) for DC:

Circuit Type	Safety Consideration	Power Limits	Typical Applications
Class 2	Fire initiation AND shock protection	100VA max at ≤30V; 5mA max at >30V	Thermostats, doorbells, security sensors, card readers
Class 3	Fire initiation only (not shock-safe)	Higher power allowed per Tables 11(A)/(B)	Some sound systems, nurse call, certain industrial controls

Class 2 circuits are designed to be inherently safe—the power levels are low enough that they won't start fires or cause dangerous shock under normal conditions. This is why Class 2 wiring has the most relaxed installation requirements. Class 3 circuits can deliver more power but require additional safeguards.

Power Source Listing Requirements

Article 721 requires Class 2 and Class 3 power sources to be:

1. Listed - By a Nationally Recognized Testing Laboratory (UL, ETL, CSA, etc.)
2. Identified - Marked as a Class 2 or Class 3 source
3. Labeled - With maximum voltage and rated current output

Acceptable power sources include:

• Listed Class 2/3 transformers
• Listed Class 2/3 power supplies
• Listed audio/video, IT, and communications equipment with limited-power circuits
• Listed battery sources identified as Class 2
• Thermocouples (exception)

Power Source Interconnection

A critical requirement in Article 721: you cannot parallel the outputs of Class 2 or Class 3 power sources unless they are specifically listed for that interconnection. This prevents contractors from connecting multiple power supplies together to increase capacity—doing so could exceed the power limitations that make Class 2/3 circuits safe.

Supply-Side Wiring

Conductors and equipment on the supply side (line-voltage side) of Class 2/3 power sources must be installed per Chapters 1-4 of the NEC. The power source itself must be protected by an overcurrent device. This requirement moved from the old 725.127 and remains in the new 725.127, but the broader context of power source requirements is now in Article 721.

Article 722: Limited-Energy Cables

Article 722 is the largest of the new Chapter 7 articles—approximately 45 pages consolidating cable requirements from six former articles (725, 760, 770, 800, 820, 840). This is where you find cable types, listing requirements, marking requirements, and substitution hierarchies.

What Article 722 Covers

• Cable listing and construction requirements
• Cable marking requirements (Section 722.100)
• Cable types and their applications
• Substitution rules (which cables can replace others)
• Installation requirements specific to cable type

Cable Marking Requirements (722.100)

All limited-energy cables must be marked per Section 722.100 and Table 722.100:

• AWG size - At least every 24 inches along the cable
• Temperature rating - Where insulation exceeds 60°C (140°F)
• Manufacturer identification - Name, trademark, or other distinctive marking
• Cable type designation - CL2, CL3, CM, FPL, etc.

Cable Types for Class 2 and Class 3 Circuits

The familiar cable designations remain, but their requirements are now consolidated in Article 722:

Cable Type	Application	Key Characteristics
CL2P / CL3P	Plenum spaces	Fire-resistant, low smoke; suitable for air-handling spaces
CL2R / CL3R	Riser applications	Fire-resistant; prevents fire spread floor-to-floor
CL2 / CL3	General purpose	Standard commercial/industrial installations
CL2X / CL3X	Residential/limited use	Dwellings; restricted in commercial applications
PLTC	Power-Limited Tray Cable	Industrial applications in cable trays

Cable Substitution Hierarchy

One of Article 722's most practical features is the consolidated cable substitution table. Higher-rated cables can substitute for lower-rated ones:

• Plenum cables (CL2P, CL3P, CMP) can substitute for any lower rating
• Riser cables (CL2R, CL3R, CMR) can substitute for general-purpose and residential
• General-purpose (CL2, CL3, CM) can substitute for residential
• Communications cables (CM types) can substitute for Class 2/3 cables when installed per Class 2/3 rules

This hierarchy means you can always use a "better" cable—plenum-rated cable works everywhere. The reverse is not true: you cannot use residential cable in a riser shaft.

Voltage Ratings

A key distinction between CL2 and CL3 cables:

• CL2 cables - Rated for voltage surges up to 150 volts
• CL3 cables - Rated for voltage surges up to 300 volts

Most security, access control, and low-voltage systems use CL2 cable. CL3 is typically required for sound systems and applications operating above Class 2 voltage limits.

Article 723: Raceways, Cable Routing Assemblies, and Cable Trays

Article 723 addresses the pathways used for limited-energy cables—raceways, cable routing assemblies, cable trays, and similar support systems. This separates pathway requirements from cable requirements, improving code organization.

What Article 723 Covers

• Raceway requirements for limited-energy systems
• Cable routing assembly specifications
• Cable tray requirements
• Support and securing requirements
• Fill calculations for limited-energy raceways

Why Separate Pathway Requirements?

Previously, raceway and cable tray requirements appeared in multiple articles—sometimes with subtle differences. Article 723 consolidates these requirements, ensuring consistent treatment whether you're running Class 2 cables, fire alarm cables, or communications cables through the same pathway.

Practical Application

When installing limited-energy cables in shared pathways (common in commercial construction), you now have a single reference point for:

• Which raceways are acceptable
• Fill limitations
• Support intervals
• Separation from power conductors within shared enclosures

Separation Requirements: What Moved

One of the most-referenced sections of the old Article 725 was 725.136—separation from power conductors. These requirements have moved to Article 720 (general requirements) with specific provisions retained in system-specific articles where needed.

Key Separation Rules (Now in Article 720)

Situation	Requirement
Same cable or raceway as power	Generally prohibited unless separated by barrier
Same enclosure (connecting to same equipment)	Minimum ¼-inch separation from power conductors
Parallel runs	2-inch minimum separation unless power is in raceway or metal-sheathed cable
Plenum spaces	Follow plenum cable requirements; separation per Article 720

Why Separation Matters

The primary concern is induced voltage from power conductors affecting Class 2/3 circuits. Maintaining separation protects both equipment and the inherent safety characteristics that allow Class 2/3 circuits to use relaxed wiring methods.

Practical Workflow for 2026 Compliance

Here's how to navigate the new structure when designing or installing Class 2/3 systems:

Step 1: Start with Article 720

Article 720 provides general requirements for all limited-energy systems. Check here first for wiring methods, materials, separation, and support requirements.

Step 2: Verify Power Source (Article 721)

Confirm your power supply is listed as Class 2 or Class 3. Check voltage/current limitations match your application. Verify interconnection is permitted if combining sources.

Step 3: Select Cables (Article 722)

Choose appropriate cable type based on installation environment (plenum, riser, general). Verify marking requirements. Check substitution table if using different cable type than specified.

Step 4: Plan Pathways (Article 723)

Select appropriate raceways or cable routing methods. Calculate fill. Plan support intervals.

Step 5: Check System-Specific Requirements (Article 725)

Review the remaining Article 725 sections for Class 2/3-specific provisions, particularly 725.2 for power/data equipment and 725.127 for supply-side wiring.

Step 6: Grounding and Protection

Reference Article 750 for grounding/bonding requirements and Article 742 for overvoltage protection.

Common Applications and Article References

Application	Typical Classification	Primary Articles (2026)
Security sensors (door contacts, PIRs)	Class 2	720, 721, 722, 725
Access control readers	Class 2	720, 721, 722, 725
Card reader to controller	Class 2	720, 721, 722, 725
IP cameras (PoE)	Class 2 or Class 4 (FMPS)	720, 721/726, 722, 725
Thermostat wiring	Class 2	720, 721, 722, 725
Doorbell/intercom	Class 2	720, 721, 722, 725
Sound systems (commercial)	Class 2 or Class 3	720, 721, 722, 725
Nurse call systems	Class 2 or Class 3	720, 721, 722, 725
Fire alarm (power-limited)	Power-Limited Fire Alarm	720, 721, 722, 760

What Hasn't Changed

While the code organization changed significantly, the underlying technical requirements remain largely consistent:

• Power limitations - Class 2 and Class 3 limits per Chapter 9 tables remain the same
• Cable ratings - CL2, CL3, plenum, riser designations unchanged
• Separation requirements - Same distances and methods, different article locations
• Listing requirements - Equipment must still be listed for its intended purpose
• Installation practices - Physical installation methods remain consistent

The 2026 reorganization is about usability, not new technical requirements. If you know how to install Class 2/3 systems properly under the 2023 code, the same practices apply—you'll just find the requirements in different (and more logical) locations.

Pro Tips for the Transition

1. Don't panic about Article 725 shrinking. The requirements moved—they didn't disappear. Your installation methods remain valid.
2. Update your code references. If you cite NEC sections in proposals or documentation, update to the new article numbers. Old citations will confuse inspectors using 2026 code.
3. Use Article 722 as your cable reference. This consolidated article is now the single source for all limited-energy cable requirements—much easier than the old system.
4. Start with Article 720. When unsure where to find a requirement, start with the general requirements article and work toward specifics.
5. Check Chapter 9 tables. Power source limitations still reference Chapter 9, Tables 11(A) and 11(B). These haven't moved.
6. Expect inspector learning curves. Inspectors are learning the new structure too. Be prepared to help them locate requirements in the new articles.

Looking Ahead: 2029 NEC

The 2026 reorganization sets the stage for even more significant changes in the 2029 NEC. Industry sources indicate the code may consolidate from its current structure to approximately 19 chapters, with limited-energy requirements potentially moving to Chapter 4. The 2026 changes—particularly the separation of concerns into Articles 720-750—prepare the code for this next evolution.

Annex L of the 2026 NEC provides guidance on the upcoming restructuring. Contractors and inspectors should familiarize themselves with the 2026 structure now, as it represents the foundation for future code development.

Related NEC 2026 Content

• NEC 2026 Article 720: General Requirements for Limited-Energy Systems
• What is Limited Energy? Understanding NEC 2026's New Terminology
• NEC 2026 Chapter 7 and 8 Changes: Complete Guide for Low Voltage Contractors
• Class 4 Fault-Managed Power: What Low Voltage Contractors Need to Know
• How NEC 2026 Affects Fire Alarm, Security, and Access Control Contractors

Stay Ahead of Code Changes

NEC 2026 adoption is rolling out state by state. Whether your jurisdiction adopts quickly or lags behind, understanding the new structure now prepares you for inspections under either code version.

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Last updated: February 2026. This article provides general guidance on NEC 2026 Articles 721-723 and Class 2/3 circuit requirements. Always consult the actual code text and your local Authority Having Jurisdiction (AHJ) for specific requirements. NEC adoption timelines vary by state and local jurisdiction.

Sources

• IAEI Magazine: NEC 2026 Significant Code Changes
• IAEI Magazine: A Look at the Proposed 2026 NEC Changes
• Electrical License Renewal: Article 725 Class 2 and Class 3 Power-Limited Circuits
• Security Sales & Integration: NEC Major Changes
• JADE Learning: Understanding Class 1, 2, and 3 Circuits
• Cmple: Understanding Cable Jacket Ratings
• Mike Holt Forums: 2026 NEC Reorganization Discussion