Ballasts: 8 of 21
.
Retrofit Recommendations
|
Existing
System
|
T8
Upgrade
|
|
F34 T12 Watt-Miser on Magnetic Ballast
|
T8 on
0.78 Ballast Factor Instant Start Ballast |
|
F40T12 (full wattage lamp--RARE!!)
on Magnetic Ballast |
T8 on |
Why have this variety of ballast factors? There is a commercial reason. Many of the T8 systems replaced existing T12 systems. Because of the higher output from the T8 lamps, you could pick a specific ballast factor that matched the light levels you previously had. Or, you might replace four T12 lamps in a fixture with three T8 lamps and run them slightly over the nominal wattage to get the same light levels.
The "rated lumens" in the catalog were measured with the lamp operating on a specific laboratory ballast. In the field the lamp is run on a different type of ballast and its light output is different from what was measured in the photometry lab. It can also be operated at higher or lower wattage resulting in more or less lumens than "rated."
The lamp's "rated" lumens taken from the catalog, multiplied by the ballast factor (BF), gives the actual lumens the end-user obtains on that particular ballast.
For example, a ballast with a BF (ballast factor) of 0.88 will result in the lamp producing 88% of rated lumens. A ballast with a BF of 1.15 will result in a lamp producing 15% more lumens than its rating.
Generally, higher BF ballast are operating the lamp at higher watts, lower BF factor ballasts are operating the lamp at lower watts.