Fluorescent lights, the symbol of institutional lighting, have come a long way since their introduction in the 1930s. No longer are they humming lamps with a dull light that gives people an unhealthy glow. Today's fluorescent light bulbs come in dozens of different varieties and colors, ranging from incandescent to natural daylight. The introduction of compact fluorescent light bulbs (CFLs) has further improved the fluorescent bulb's reputation--today they are found in many different environments, from workplaces to homes.
Make sure you are working with a T8 fixture and ballast by checking both the labeling and the rating. Fluorescent bulbs come in a variety of styles. The most common style, the T12, is a 40-watt bulb that has long been the standard in construction. However, this bulb is being replaced by the T8, which is a more efficient 32-watt bulb that uses more advanced technology.
Calculate the difference in cost between running a T8 lamp in a T8 ballast versus running a T12 lamp in the same ballast. As expanded upon in Step 5, both the efficiency and the life of the bulb will be vastly reduced. Although the two bulbs are the same size, they are not the same thing. The older, wider T12 bulbs use a magnetic ballast that has been around since fluorescent lights were first introduced. This ballast makes a distinctive humming noise. T8 lights use electronic ballasts, which is a newer technology that is silent and far more efficient. This incompatibility costs efficiency, so be sure the savings are sufficient.
Remove the T8 bulb from the fixture by twisting to unlock it from its mount, and then pulling it down. Repeat this until you have removed all of the bulbs. Handle the bulbs gently to avoid breaking them and releasing toxic gas. Dispose of the bulbs properly according to state and federal laws.
Reverse the above process to insert the T12 bulbs. On most ballast setups, the lights are as close together as possible to save space. The T12 is a full half inch bigger than the T8, so you will most likely not be able to fit as many bulbs into a given fixture (resulting in dimmer lighting).
When ballasts and lights are mixed incorrectly, problems arise. In particular, the bulbs' brightness and efficiency decline rapidly. In this case, a T12 bulb's brightness decreases by 38 percent, from 440 foot-candles to 287. Although the power drawn also decreases by about 30 percent, this reduction is a false savings. Installing a bulb in the wrong ballast shortens its lifespan dramatically. This is a result of the different milliamp ratings of the ballast and the bulb. The T8 provides 285 milliamps while the T12 needs 430. Underdriving the light like this causes problems with the starting mechanism, destroying the bulb and potentially the ballast. However, the two should work together, so if it is absolutely necessary, a T12 bulb can be run on a T8 ballast.