Hanging by a Thread

There is a new technology using low-voltage lighting power distribution at 30 volts (V) or less where the suspended ceiling grid is a lighting power distribution system. Article 410, covering luminaires, and Article 411, covering low-voltage lighting systems at 30V or less, are the two primary lighting installation articles in the National Electrical Code (NEC) pertaining to this new technology. To make use of the new technology, you must understand the relationship of these two articles with respect to ceiling-grid low-voltage lighting system power distribution.

The electrical industry needs additional information about the possible expanded use of this new low-voltage power distribution system for nonlighting systems and identified associated listed components for functions other than lighting, such as audio/video equipment; heating, ventilating and air conditioning (HVAC) actuators; air/temperature sensing devices; information technology equipment; and more. Information on various old and new products for lighting and other uses will be provided where these products are being adapted to work within the framework of the NEC for this new technology.

This new technology was derived by the realization of some people in the electrical industry that supplying permanent power for lights, receptacles and other equipment in an office area within a building did not permit flexibility or ease of revision, remodeling, or reconstruction within these areas. A segment or coalition of the construction-manufacturing community began work on a method of establishing an easier and less expensive method of providing power for general lighting loads and task lighting in the office area.

The designers and developers of this new technology had to determine what the NEC would permit and then integrate the existing systems into a highly flexible wiring system. Decisions had to be made about the power source to be used, how to distribute power to the equipment, the type of connections to the power source that would be both safe and compliant with the NEC, and the overall functional design of the system. In addition, determining the power level for any new system was a major concern since, as voltage and amperage of a power system increase, the system becomes less flexible.

The Code provided the technical basis for using low-voltage power for the ceiling grid low-voltage power distribution in Article 725 and similar but related articles. For example, Article 640 covered audio signal processing, amplification and reproduction equipment (Audio and video equipment) and permits Class 2 and 3 power and wiring methods in accordance with Article 725. Heating and air conditioning systems, designed with Class 2 and 3 power systems for heating and air conditioning controls and thermostats as well as control of variable air volume dampers, rely on Article 430 for motors, Article 440 for air conditioning systems and Article 422 for appliances. While Class 2 or 3 power-limited systems are often used for motor controls, as noted in Section 430.72 within Article 430, Article 725 generally covers remote control, signaling and power-limited circuits; therefore, the product’s design coalition determined that Article 725 was the key to providing the power for this low-voltage lighting ceiling-grid distribution system.

Before covering the requirements for Class 2 and Class 3 remote-control, signaling and power-limited circuits found within Article 725, basic Code arrangement must first be understood. Section 90.3 states the first four chapters (Chapter 1 covering general electrical requirements, Chapter 2 covering wiring and protection, Chapter 3 covering wiring methods and materials, and Chapter 4 covering equipment for general use) are general electrical requirements. Chapters 5, 6 and 7 are specialty chapters dealing with special occupancies, special equipment, or other similar types of special conditions, respectively, involving these special occupancies or equipment. Since these three specialty chapters cover special equipment and occupancies, the general rules and requirements found in the first four chapters can be supplemented or modified by the information found in Chapters 5, 6 and 7. This means all of the general requirements in Chapters 1 through 4 must be followed unless special equipment, special occupancies or special conditions require or permit us to deviate from the general rules. Specific requirements for low-voltage circuits covered in Article 725 can add to or amend any requirements for a similar circuit found in Chapters 1 through 4.

Studying the acceptance of this new technology for lighting and then viewing the expansion of the supporting technology with the electrical industry’s rapid implementation of this new lighting concept, coupled with other innovative applications, are key points underscoring the need for this technology.

To ensure you fully understand this technology, I will continue this topic next month.

ODE is a staff engineering associate at Underwriters Laboratories Inc., based in Peoria, Ariz. He can be reached at 919.949.2576 and mark.c.ode@us.ul.com.

About the Author

Mark C. Ode

Fire/Life Safety Columnist and Code Contributor
Mark C. Ode is a lead engineering associate for Energy & Power Technologies at Underwriters Laboratories Inc. and can be reached at 919.949.2576 and Mark.C.Ode@ul.com .

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