We have Fluorescent Ballasts - Sign, Electronic and Magnetic

Electronic ballasts use semiconductor technology to convert incoming 60-cycle power to drive the lamps with high-frequency current of 20,000 cycles per second or more. Electronic ballasts are more efficient in a number of ways. Most notably, they waste less power internally than magnetic ballasts, saving 3 to 8 watts per ballast. Their higher frequency drives lamps about 10 percent more efficiently than do 60-cycle magnetic ballasts. And those electronic ballasts with dimming capability save energy in multiple ways, from lumen compensation that eliminates the need to overlight spaces when the lamps are new to the tens of percentage points in savings that come from reducing electric light levels when daylight is available.

Some well-publicized failures of certain early-generation electronic ballasts made users wary of the technology's reliability. Over the past decade, however, manufacturers have worked hard to dispel these concerns, with a combination of improved design and higher quality control standards in components and assembly. Today, electronic ballasts from established suppliers are just as reliable, if not more so, than magnetic ballasts.

How to Make the Best Choice

Ballasts are often the most expensive first-cost component of a lighting retrofit. Energy efficient magnetic ballasts typically cost $12 to $20 each, in volumes of 1,000 units. Nondimming electronic ballasts typically cost $14 to $30 each, and dimming models are priced from the low $30s to more than $50 each. Remember to consider lifecycle cost (including energy cost savings) as well as first cost when making your choice.

Beyond the basic split between energy efficient magnetics and electronics, a dizzying array of other performance criteria distinguish ballasts:

* There are three traditional starting methods--rapid start, instant start, and preheat--plus a new approach called programmed start, which minimizes wear and tear on lamps during startup.

* Ballasts vary in ballast factor, ballast efficacy factor, current crest factor, power factor, total harmonic distortion, flicker index, audible sound rating, transient protection, and radio interference.

* In addition, ballasts are designed to operate with specific lamps. If lamp and ballast are mismatched, the life and performance of both can suffer.

Users should consult with a qualified lighting designer, but the following general guidelines can apply in many instances:

High-frequency electronic ballasts with T8 lamps are typically the most efficient solution with the lowest lifecycle cost. There are some situations, however, in which it makes sense to use magnetic ballasts. These include settings where the equipment will operate in extremely hot or cold conditions and locations where there is a lot of sensitive electronic equipment. Electronic ballasts have been known to interfere with book detection systems in libraries, inventory security systems in stores, recording studio equipment, and some electronic medical equipment. Because they operate at much lower frequency, magnetic ballasts do not cause such interference and may be a safer choice in such settings.

Instant-start ballasts are appropriate for applications in which lights will be left on for more than three hours at a time. For shorter-duty-cycle applications, including settings with occupancy sensors, the new family of programmed-start ballasts should be considered. Weigh the higher first cost of the programmed-start ballasts against the fact that lamps will last longer with them than when operated on instant-start ballasts. With the advent of programmed-start ballasts, rapid-start designs, which used to be the ballast of choice for short-duty-cycle applications, are rarely called for.