21.1 Remote-Control, Signaling & Power-Limited Circuits: Class 1, 2 & 3 (2026 Articles 206, 720–725)

The 2026 reorganization

DLI's knowledge areas list Class 1, 2, and 3 remote-control, signaling, and power-limited circuits and the general requirements for limited-energy system wiring methods. The 2026 NEC moved these rules into a new structure so the same requirements are not repeated in every article:

Chapter 8 now covers only communications circuits outside and entering buildings; inside the building, communications wiring follows the Chapter 7 limited-energy rules.

Circuit classes

Class 1 rules

• Conductors: 18 AWG and 16 AWG Class 1 conductors are permitted where protected at 7 A and 10 A; larger conductors follow Table 310.16 and 240.4.
• Same raceway with power: Class 1 circuit conductors may share a raceway or enclosure with power-supply conductors only where functionally associated with the equipment they supply.
• Safety-control circuits: remote-control circuits for safety-control equipment are Class 1 where failure of the equipment to operate would introduce a direct fire or life hazard. Where physical damage to such circuits would create a hazard, all their conductors must be in RMC, IMC, PVC, EMT, Type MI or MC cable, or otherwise protected. Room thermostats, water temperature regulators, and similar household heating and air-conditioning controls are not safety-control equipment.

Class 2 and Class 3 circuits

Power sources (Article 721)

A Class 2 or Class 3 circuit must be supplied by a listed power source: a Class 2 or 3 transformer, a Class 2 or 3 power supply, other listed equipment marked to identify the Class 2 or 3 power source, listed ITE equipment, or a dry-cell battery for Class 2. The outputs of Class 2 and 3 power sources may not be paralleled or otherwise interconnected unless listed for that use, because combining them can exceed the class limits.

Power source limits (Chapter 9, Tables 11(A) and 11(B))

Chapter 9 Table 11(A) (ac) and Table 11(B) (dc) set the maximum voltage, current, and power for Class 2 and Class 3 power sources. Each table has two halves: inherently limited sources, which need no overcurrent protection, and sources not inherently limited, which require overcurrent protection. Two values are worth remembering: an inherently limited Class 2 ac source over 20 V and up to 30 V has a maximum nameplate rating of 100 VA, and an inherently limited Class 3 ac source over 30 V and up to 100 V is also limited to 100 VA. Equipment listed and marked as Class 2 or Class 3 already meets these limits, so in the field you verify the marking rather than calculating.

Separation from other systems

• Class 2 and 3 conductors may not be placed in any raceway, cable, compartment, outlet box, junction box, or cable tray with conductors of electric light, power, Class 1, nonpower-limited fire alarm, or medium-power network-powered broadband circuits, unless separated by a barrier or the Code specifically permits it.
• In enclosures where power conductors enter only to connect to the same equipment, Class 2 and 3 conductors must keep at least ¼ in. of separation or be routed to avoid the power conductors.
• In other installations, such as open wiring in a building, Class 2 and 3 conductors must be kept at least 2 in. from power, Class 1, and NPLFA conductors, unless the power conductors are in raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, Type TC, or Type UF cable, or the Class 2 and 3 conductors are in raceway.
• Class 2 and Class 3 circuits may share a cable or raceway with each other where the Class 2 conductors are insulated for Class 3 use, and with communications and power-limited fire alarm circuits where permitted.

Cable types and substitutions (Article 722)

Class 3 cable may substitute for Class 2 cable, and a higher-rated cable (plenum over riser over general purpose) may always substitute for a lower-rated one, never the reverse.

Power over Ethernet and other power on data cable

Class 2 and Class 3 circuits that carry power over communications cables, such as PoE to cameras, access points, and LED luminaires, have ampacity limits that depend on conductor size, temperature rating, and bundle size. For larger bundles and higher power levels, use cables marked "-LP" (limited power) with the marked current rating, or the ampacity table for the bundle size.

Installation rules (Article 720 and Article 300)

• Access to equipment (formerly 725.21): cables and equipment may not be installed in a way that prevents removal of panels, including suspended ceiling panels, needed to reach electrical equipment.
• Workmanship and support (formerly 725.24): cables must be installed in a neat and workmanlike manner, supported by the building structure with straps, staples, hangers, or cable ties listed and identified for securement and support, and not damaged. They may not be supported by ceiling grids or ceiling-support wires, or strapped to the outside of raceways (except Class 2 cables supported by a raceway that supplies power to the equipment they control).
• Penetrations: openings through fire-resistant-rated walls, floors, and ceilings must be firestopped.
• Abandoned cables (formerly 725.25): the accessible portion of abandoned Class 2, Class 3, and PLTC cables must be removed. Cables identified for future use with a tag of sufficient durability are not considered abandoned.

Worked example: a commercial ceiling

A security contractor runs CL2 cable above a suspended ceiling used as a return-air plenum.

1. Cable type: the space is a plenum, so the cable must be CL2P (or a permitted substitute such as CMP or CL3P).
2. Support: fasten the cable to the structure with listed supports or J-hooks; do not lay it on the ceiling tiles or tie it to grid wires.
3. Separation: do not pull the CL2P cable into the same raceway or box as 120 V lighting conductors.
4. Old cable: remove the accessible portions of the abandoned alarm cable that the new system replaced, or tag any cable kept for future use.