Low voltage cabling for commercial buildings
Beyond the data network, a building runs on low-voltage cable: door hardware, AV, paging, intercoms and sensors. Cablify runs and labels it to the same standard as the network cabling, so every system has a record.
How the NEC sorts low-voltage systems
Low voltage is a trade term. The National Electrical Code sorts these systems by what they carry, and each has its own article for cable types, ratings and installation.
| System | Examples | 2023 NEC |
|---|---|---|
| Communications | Voice, data and coaxial TV cable | Articles 800 and 805 |
| Optical fiber | Backbone and campus fiber | Article 770 |
| Class 2 and Class 3 circuits | Door hardware, thermostats, sensors, many AV control circuits | Article 725, with cable rules in Article 722 |
| Class 1 circuits | Some control and signaling circuits | Article 724 |
| Fire alarm | Detection and notification circuits | Article 760 |
| Audio | Paging and sound systems | Article 640 |
| Class 4 fault-managed power | A newer way to deliver power over cable | Article 726 |
Class 2 limits and separation
Class 2 is the circuit type behind much of the door hardware, sensors and controls in a building. At 30 volts or less, a Class 2 power supply is limited to 100 VA. That limit is what lets Class 2 cable be installed without the wiring methods power circuits need.
Class 2 and 3 cable has to stay at least 2 inches from power and Class 1 conductors unless a barrier or raceway separates them, under NEC 725.136. Sharing a conduit with power is not allowed as a rule.
- Separate pathways from line-voltage wiring
- Cable listed for the space: plenum, riser or general purpose
- Supported from the building structure
- Labeled at both ends and recorded with the system it serves
- Firestopping restored at every rated penetration
Systems we cable
We run, terminate and label the cable for these systems. The system vendor or your integrator programs the equipment.
Door hardware
Electrified locks, exit devices, door contacts and automatic operators. See access control.
AV and conference rooms
Display, camera, control panel and table connection cable, with pathways to the AV rack.
Paging and background audio
Speaker cable to ceiling and horn speakers, zoned the way the building is used.
Intercom and video entry
Door stations, master stations and the cable to the gate or lobby.
Sensors and controls
Thermostats, occupancy sensors and other building control devices on Class 2 circuits.
Radio coverage pathways
Riser and ceiling pathways for in-building radio and cellular systems. See commercial real estate.
Licensing differs by state
There is no national low-voltage license. These are examples from state licensing bodies; cities can add their own rules, and we confirm what applies when we scope the job.
| State | Licensing body | Classification | What it covers |
|---|---|---|---|
| California | Contractors State License Board | C-7 Low Voltage Systems | Energy-limited systems not exceeding 91 volts; low-voltage fire alarm is excluded |
| Georgia | Division of Low-voltage Contractors | LV-A, LV-T, LV-G, LV-U | Alarm, telecommunications, general and unrestricted low-voltage work |
| North Carolina | Board of Examiners of Electrical Contractors | SP-FA/LV | Special restricted fire alarm and low-voltage work |
| Washington | Department of Labor and Industries | 06 Limited energy system | Signaling and power-limited circuits; the 09 telecommunications specialty excludes access control and intrusion alarms |
| Florida | Electrical Contractors’ Licensing Board | Limited Energy Systems Specialty | Systems up to 98 volts RMS, excluding alarm work, which needs an alarm system contractor license |
| Texas | Department of Public Safety, Private Security Program | Alarm and access control company licensing | Alarm, CCTV and electronic access control installers; a state electrician license is not required for Class 1, 2 or 3 circuits |
Common questions
What counts as low voltage?
It depends on who is asking. The NEC uses circuit classes, such as Class 2, rather than one voltage. State licenses draw their own lines: California’s C-7 covers energy-limited systems up to 91 volts, and Florida’s limited energy specialty goes up to 98 volts RMS.
Do you need a license for low voltage wiring?
In many states, yes, and the license depends on the system. Some states license low-voltage work broadly, some license only alarm and access control installers, and some leave it to cities. We check the rules for your state and city before the job.
Can low voltage cable share a conduit with power?
Not as a rule. The NEC requires Class 2 and Class 3 cable to be separated from power and Class 1 conductors, with limited exceptions such as a listed barrier.
What is a Class 2 circuit?
A power-limited circuit defined by the NEC. At 30 volts or less, the power source is limited to 100 VA, which keeps the shock and fire risk low enough for lighter wiring methods.
Request a low voltage cabling quote
Send the address, the systems involved and the number of devices for each. Drawings or a device schedule help us price the runs.