By Jerry Plank
The noted novelist and teacher Pearl S. Buck was the first American woman to receive the Nobel Prize for literature and also earned the Pulitzer Prize for her novel The Good Earth. Unknown to Buck herself, she was also a technologist, who made this insightful statement: “If you want to understand today, you have to search yesterday.” Buck captured the essence of what happens in the field of product safety testing every day as we use the past to predict the future.
By relying on the past, professionals involved in product safety testing seek to reduce the risk of fire and electrical shock when installing and operating electrical products. It is no secret that past failures of lighting products guide current requirements. Unfortunately, as lighting moves into the “digital age” there is a concerted move by some— knowingly or unknowingly—to lessen or subjugate luminaire requirements when using Class 2 wiring. A conservative approach to new technologies has served industry well for many years in reducing risks, and a careless approach to Class 2 wiring will have a cost.
One issue that keeps surfacing is the use of wires, cables and flexible cords to connect lighting products to a source of supply in the field. Even the use of the terms wire, cord or cable are not standardized or described in most safety standards. Why? Read on as we dig deeper into the confusion surrounding what wire or cable or cord can be used by an electrician to connect Class 2 lighting products to a source of supply.
The confusion surrounding what wire or cable or cord can be used to connect low-voltage LED products to the supply has to do with the use of Class 2 power supplies or “drivers.” To some, as the output of low-voltage lighting products is Class 2 and limited in energy, the risk of fire is eliminated. Or is it?
A simple Internet search of “low-voltage fires” will reveal many situations where low-voltage wiring did create unforeseen hazards leading to a fire. Further, what about hazards, other than fire or electrical shock? One such example was a notorious fire where the major cause of death was due to wires, cables and cords adjacent to the fire, which when ignited created a toxic plume of smoke. The fire at the MGM Grand in 1980 took the life of 85 people, most by toxic smoke inhalation. The insulating materials used in the MGM Grand on the wires, cables and cords all contributed to producing the toxic smoke when ignited.
In fact, an electrican that uses flexible cord or wires to connect the low-voltage luminaire to a remote Class 2 power supply or “driver” supply in the plenum is in violation of the NEC (NFPA-70), Article 725, as the issue of flammability and smoke development has not been addressed.
What the ANSI/UL safety standards fail to cover or discuss, is the toxic fumes or smoke that could be emitted or flame spread by the materials used in the components and wire of a luminaire. The smoke density requirements covered in UL 13, The Safety Standard for Power-Limited Circuit Cables, address smoke and fire testing for typical communication cable used with luminaires today such as CL2, CL3, CL2P, etc. The contribution of toxic smoke generated by burning wires and cables can be substantial due to the quantity of bundled cables that now run through buildings due to computers and the like. Only plenum-rated cables should be used in a plenum on Class 2 luminaires where the flame spread and smoke density has been evaluated.
A conservative approach to new
technologies has served industry well for
many years in reducing risks, and a careless
approach to Class 2 wiring will have a cost
It is now time for greater coordination between the safety standards of ANSI/UL and the National Fire Protection Association (which publishes the National Electrical Code and literally hundreds of other safety codes) codes used by municipal electrical inspectors and fire officials in North America. All involved in luminaire production should get engaged in the process of writing safety standards as any negative experience using LED Class 2 lighting products affects us all. We should not repeat past mistakes that could lead to potential loss of life when a fire erupts in a building. The lighting industry has enjoyed an excellent record on the safety of products and all involved should seek to refine the standards used to reduce risks on Class 2 circuits.