Low-voltage codes & standards

Governs remote-control, signaling, and power-limited circuits that are not an integral part of a device or appliance — thermostats, access control, intercom, nurse call, and most building-automation wiring. Class 2 and 3 circuits are energy-limited at the power source (a listed Class 2 supply or transformer).

Article 725 is the workhorse low-voltage article. The key idea is the power-limited source: a listed Class 2 supply caps available energy so the circuit is considered safe from a fire-ignition and shock standpoint, which in turn relaxes the wiring methods (smaller conductors, no conduit required in many cases). That relaxation is conditional — Class 2 conductors must be separated from power and Class 1 conductors (§725.136), cables must carry the correct listing (CL2/CL3, with CL2P/CL2R for plenum/riser), and the power-limited rating is voided if you re-power the circuit from a non-listed source. The 2023 edition reorganized the cable-substitution hierarchy and tightened abandoned-cable removal. NEC 2026 SPLITS this article: Class 1 remote-control and signaling circuits move out to the new Article 724 (strict 30 V / 1000 VA limit) and the legacy "low-voltage" terminology is replaced throughout with "limited-energy" to align with the physical parameter.

New for NEC 2026. Regulates Fault-Managed Power Systems (also called digital electricity or smart transmission), which deliver up to 450 V over communications-style cabling by continuously sensing for faults and shutting down within milliseconds when one occurs.

Article 726 is the headline limited-energy addition in NEC 2026. Class 4 FMPS uses paired transmitter/receiver units to push DC power up to ~450 V down small-gauge cables that look more like Cat 6 than line-voltage NM. The transmitter continuously monitors line impedance and trips the circuit in milliseconds on any contact or fault — making the run dynamically "safe-to-touch" between pulses despite the voltage. The architecture targets long-run, low-loss distribution: PoE-style cabling out to lighting clusters, small motors, EV trickle charging in commercial garages, and microgrid sub-distribution. Listed FMPS transmitters, receivers, and cables are required; field-improvised conversions are prohibited.

Governs the installation wiring of fire alarm systems — initiating device circuits (IDC), notification appliance circuits (NAC), and signaling line circuits (SLC) — for both power-limited (PLFA) and non-power-limited (NPLFA) systems. Works alongside NFPA 72, which governs system design, operation, and inspection.

Article 760 mirrors Article 725 but for fire alarm: power-limited fire alarm (PLFA) circuits get relaxed wiring methods in exchange for an energy-limited, listed source, while non-power-limited (NPLFA) circuits follow Chapter 3 wiring methods. Fire alarm cable carries FPL/FPLR/FPLP listings paralleling the CL2 family. The defining requirement is circuit integrity and survivability — fire alarm conductors must be kept independent of power and other low-voltage systems (§760.136), and red jacket / dedicated raceway identification is expected. NFPA 72 is the companion standard you must read for device spacing, supervision, and acceptance testing.

Governs the installation of optical fiber cables and raceways. Classifies fiber as nonconductive (OFN), conductive (OFC — contains a metallic strength/armor member), or composite (optical fibers plus current-carrying conductors), each with plenum/riser/general listings (OFNP, OFNR, OFCP, etc.).

Even though glass fiber carries no current, Article 770 exists because the cable jacket is a fire-load and because conductive (OFC) cables contain metallic members that must be bonded and grounded like any other conductor entering a building. The article sets the listing/marking hierarchy, the plenum and riser flame requirements, and the separation and grounding rules for conductive types. The 2023 edition aligned the substitution hierarchy and abandoned-cable rules with Articles 725/800.

The general article for communications wiring — telephone, structured data cabling, and broadband — reorganized in the 2020 NEC as the parent of the Chapter 8 communications articles. Defines the CM cable family (CM, CMR, CMP, CMX) and the bonding, grounding, and listing rules common to limited-energy communications systems.

Article 800 (with §§805/820/830 for specific services) is where structured cabling lives in the NEC. It sets the cable listing hierarchy that governs Cat 5e/6/6A installs — CMP for plenum, CMR for risers, CM/CMX for general use — plus the primary protector, bonding, and grounding requirements where communications conductors enter a building. It works hand-in-glove with the ANSI/TIA-568 family (which sets transmission performance and the 100 m channel) and TIA-569 (pathways). The 2023 edition continued the limited-energy reorganization and abandoned-cable cleanup that started in 2020. In NEC 2026 the historical independence of Chapter 8 is ELIMINATED — communications are folded fully into Chapter 7 and become subject to general NEC installation rules. New §800.48 also restricts unlisted outside-plant (OSP) communications cables to a maximum 15 m (50 ft) run inside the building before termination, to keep outdoor surge energies from migrating in.

Revised PPE rule for construction. Took effect January 13, 2025. PPE must be of safe design and properly fit each employee.

The amendment explicitly closes the "one-size-fits-all" loophole. PPE that does not fit the worker (gloves too large, eye protection that slips, hard hats poorly sized) is no longer compliant even if the item itself is rated correctly. This is now a frequent OSHA citation driver.

Trenches and excavations on construction sites. Protective system required at ≥5 ft (sloping, benching, shoring, or shielding); RPE-designed system required ≥20 ft.

Daily inspection by a competent person, spoils kept ≥2 ft from edge, ladder/ramp egress within 25 ft of workers in trenches ≥4 ft. Trench collapse is the single most common fatal injury in plumbing service-line work.

1910.146 is the General Industry permit-required confined-space rule; 1926 Subpart AA is the Construction-industry equivalent. Atmospheric testing order: O₂ (19.5–23.5%), combustibles (<10% LEL), toxics.

Many plumbing and HVAC service spaces qualify: tanks, vaults, sewer manholes, crawlspaces, large duct/AHU interiors. Permit, attendant, retrieval system, communication, and a written rescue plan are all required for permit-required confined spaces.

Notice of Proposed Rulemaking 89 FR 70698, published August 30, 2024. Informal hearing concluded July 2, 2025; post-hearing comments closed October 30, 2025. No final standard yet.

Until a federal standard is finalized, OSHA enforces heat hazards through the General Duty Clause and the 2022 National Emphasis Program on heat. State standards exist in California (Title 8 §3395), Colorado, Minnesota, Oregon, Washington, and Maryland (proposed). Nevada's heat regulation R131-24AP was adopted October 28, 2024 and approved by the Legislative Commission November 15, 2024, with enforcement beginning April 29, 2025.