3 Factors to Consider in Fluorescent Ballasts
Unless you're an electrician, you've probably never changed a ballast. Chances are, when your garage fixture or kitchen light went out, you changed the bulbs, and when that didn't work, you went to an overpriced hardware store and bought a brand-new fixture. Sound familiar? Unfortunately, you could've saved a lot of money by switching out the ballast—an investment of only $10 to $15.
But with so many options out there, how would you know which ballast to pick? The truth is, it's pretty simple. There are tons of fluorescent ballasts to choose from (we have nearly 300 on our site!), but most business owners and even homeowners will find it easy to wade through that seemingly never-ending selection if they concentrate on just 3 key specs: Bulb type, start method, and ballast factor.
Needless to say, this is the most important part. If you don't know what type of fluorescent bulb you're using, you're going to have a hard time figuring out which type of fluorescent ballast to buy. Fortunately, most fluorescent fixtures will use one of three common bulb types: An F40T12 (4' long; 1.5" in diameter), an F32T8 (4' long; 1" in diameter) or an F54T5 (46" long; 0.625" in diameter). If your bulbs don't meet one of these descriptions, you'll need to check the etching near one of the ends of the fluorescent bulb (a good idea even if you think you know the bulb type).
Once you've determined what type of fluorescent bulbs you have, don't burn them out prematurely by choosing a ballast with the wrong starting method. As discussed in a previous article on how to extend the life of a light bulb, an instant start ballast hits the fluorescent bulb cathodes with about 600 volts every time you flip the light switch. As you might imagine, the bulb can only stand so many of those on/off switches. Consider where your fixture is installed. Offices, boardrooms, and retail spaces tend to stay lit for long periods, so use an instant start ballast should be fine, as long as you don't switch the lights off and on more than about 3-4 times a day. Hallways, stairwells, and bathrooms are switched much more frequently, especially since the lighting in these areas is often controlled by an occupancy sensor. In these areas, it's best to use a programmed start ballast, which will heat the bulb cathodes more slowly and prolong its life.
Finally, you need to consider light output. "What?" you say. "You mean the bulb isn't exactly the brightness it says it is on the label?" Nope. The light output shown on a fluorescent bulb's label, expressed in lumens, is figured using a normal light output ballast with a ballast factor between 0.77 and 1.1. A normal ballast factor is usually the right option, for "normal" circumstances. But if you don't need your room quite as bright, you can save electricity by using a low output ballast with a ballast factor below 0.77. On the other hand, if you are lighting a warehouse or manufacturing facility where brightness is important, you will need a high output ballast with a ballast factor above 1.1, which will push the bulb to be 10% or more brighter than stated on the label.
Of course, if you need something more specialized like a sign ballast, dimming ballast, or circline ballast, you'll likely need an equally specialized electrician. The same principles still hold true, however, so if you need to call an electrician, at least he'll be impressed by how much you know!