APPLICABLE CODES
Last updated
Last updated
Article 411 covers lighting systems and their associated components operating at no more than 30 volts AC or 60 volts DC. These voltages are derated if wet contact is likely to occur.
Low Voltage Lighting Systems. The National Electric Code requires that low voltage lighting equipment is certified to the appropriate UL standard for lighting purposes. This means that all electrical components, fixtures, wires, and drivers need to be certified to the correct standard.
As seen in Figure 5, the Code Requirement Tree, Article 411 is the overarching code. This article then directs/references NEC 725.130 and Chapter 3 (wiring methods and materials).
Most low voltage cable is grouped into three (3) fire safety categories:
1) Plenum Cable
2) Riser Cable
3) General Purpose Cable
Plenum Cable
Plenum Cables are the highest rated in terms of fire resistance.
Riser Cable
Riser cables are designed to meet fire resistance standards for installation within a vertical riser, i.e., a run that spans more than one level of a building.
General Purpose Cable
General purpose cables are used for general purpose spaces. These are the least fire-resistant cable types
Type CM – Communications Wires and Cables
Type CL2 & CL3 – Class 2 and Class 3 Remote-control, signaling, and power limited cables
Type PLTC – Power-Limited tray cable.
SPECIFYING CABLE
Within this category, it is recommended to use plenum cable because it is rated for most inwall applications. Examples of plenum cable types are CL2P or CL3P cable. This type of designation will be printed on the surface of nonmetallic cable jackets.
Per the Underwriter’s Laboratory, “the UL symbol on the product and the Certification Mark of UL on the attached tag, reel, or on the smallest unit container in which the product is packaged is the only method provided by UL to identify products manufactured under its Certification and Follow-Up Service. The Certification Mark for these products includes the UL symbol, the words ‘CERTIFIED’ and ‘SAFETY,’ the geographic identifier(s), and a file number.”
Note also that the Certification Mark for this category requires the use of a holographic label.
For more detailed information, please reference the UL-White-Book “GUIDE INFORMATION FOR ELECTRICAL EQUIPMENT THE WHITE BOOK 2015-16.”
DO YOU NEED TO SPECIFY SPECIAL SWITCHES OR LIGHTS?
Due to its power limitations, a Class 2 circuit is considered safe from a fire initiation standpoint and provides acceptable protection from electrical shock. Thus, from a regulatory standpoint (UL), there are no safety standards that have been written for low voltage Class 2 switches. No special switches are needed for a Class 2 Distributed DC System. A standard wall switch that is typically rated at 15A, 120VAC can be used. Recall that this is a 24VDC system that can deliver up to 4.1 Amperes – well below the 15A 120VAC ratings of a standard light switch.
Based on the above, a Class 2 Distributed DC System can use a switch that does not have a regulatory mark. An example of this is shown in Figure 10, the Leviton 56021-2W 3 Amp, 24 Volt AC/DC, Switch Decora Plus Quiet Rocker.
One does, however, need to specify special integrated LED fixtures. Fixtures must be 24VDC certified to UL 2108 standard. Regular/120VAC integrated LED fixtures will not work. Figure 12 is an example of a low voltage down light available from CLEANLIFE. This fixture is certified to the UL 2108 standard and comes with the mounting plate shown. This new construction rough-in plate is used to secure the downlight in place to the studs instead of traditional recessed can lighting fixture. This can help to save cost and improve ease of installation while meeting code requirements. This will fit up to 24” spaced studs/joists.
NEC 725.130 covers the wiring methods for the load side of Class 2 systems and defines the insulation requirements for the cable per 725.179 (Listing and Marking of Class 2 Type PLTC Cables). The wiring then should be installed in accordance with 725.133 (Installation in Enclosures, Compartments, etc.) and 725.154 (Applications of Cables).
