• Home
• Policies
• Campus Initiatives
• Energy Consumption Reports
• Sustainability
• Lighting Catalog
• Building Automation System
• Weather History
• FAQ
• Physical Plant Home
• - Physical Plant Staff

Learn More

Lighting: T12 to T8 Conversion

<< back

Older linear florescent fixtures used throughout most of the older buildings on the WMU campus used T12 type magnetic ballasts. This type of ballast operates at 60 Hz and requires an additional 15% more power beyond the lamp requirements to operate. Studies have shown that although the light flicker generated at a 60 Hz cycle is undetectable to the human eye, over time can affect performance, concentration and the overall health of some individuals.  Newer T8 electronic ballasts operate at 20,000 Hz. At this cycle rate, energy is trickled to the florescent lamps at a smaller but much faster rate making them considerably more efficient. The side effects on human beings are also eliminated. The following paragraphs discuss lighting flicker and its affects on the human body.


Are there any health effects associated with light flicker?
Although humans cannot see fluorescent lights flicker, the sensory system in some individuals can somehow detect the flicker. Ever since fluorescent lighting was introduced in workplaces, there have been complaints about headaches, eye strain and general eye discomfort. These complaints have been associated with the light flicker from fluorescent lights. When compared to regular fluorescent lights with magnetic ballasts, the use of high frequency electronic ballasts (20,000 Hz or higher) in fluorescent lights resulted in more than a 50% drop in complaints of eye strain and headaches. There tended to be fewer complaints of headaches among workers on higher floors compared to those closer to ground level; that is, workers exposed to more natural light experienced fewer health effects.
 [Wilkins, A. J., Nimmo-Smith, I., Slater, A. & Bedocs, L. (1989). Fluorescent lighting, headaches and eye-strain. Lighting Research and Technology, vol. 21, 11-18]

What can be done to reduce or eliminate light flicker?
Some types of ballasts can reduce flicker considerably. New, energy-efficient electronic ballasts take the 60 Hz power and convert it to voltages at a much higher frequency (20,000 - 60,000 Hz). The resulting flicker frequency (twice the supplied power frequency, 40 -120 kHz) is so high that the human eye cannot detect any fluctuation in the light intensity - essentially flicker-free. An added benefit is that electronic ballasts produce less hum than that emitted by other kinds of ballasts.