High Efficiency Fluorescent Ballasts

Replacing standard fluorescent lamps with high-efficiency fluorescent lamps saves energy and money; replacing ballasts can result in even greater savings. If your facility is in use more than 8 hours per day, it may be cost-effective to replace standard ballasts immediately. Although ballasts are expensive, and retrofitting may not occur immediately, standard ballasts should be replaced with energy-efficient ballasts upon burn-out. Also, if existing ballasts are reaching the end of their rated life (15 to 20 years), now is a good time to replace them as a group. Group replacement reduces labor costs and allows for volume purchase discounts. High-efficiency ballasts should always be specified for new fixtures.

How Ballasts Work

To produce light, a fluorescent lamp passes an arc of electricity from one end of the lamp to the other. The arc interacts with mercury vapor, producing radiant energy. When radiant energy strikes the phosphor coating on the inside of the lamp, the phosphor gives off light. After the arc is established, only a low voltage is required to maintain it. (High voltage will burn the lamp out prematurely.) The ballast is placed in the circuit to provide a high starting voltage followed by a current-limiting function.

Standard Ballasts

Standard ballasts use a combination of inductive and capacitive networks to control current to the lamps. Inductors are aluminum coils wrapped around laminated iron cores.

Energy-Efficient Magnetic Ballasts

Energy-efficient magnetic ballasts are simply improved versions of the standard ballasts. Instead of aluminum, these ballasts have copper wire coils, and the iron cores are larger. The copper has lower resistance and the larger iron core generates less heat inside the ballast. These two factors result in efficiency improvements.

Hybrid Ballasts

In order to initially light rapid start lamps, an initial voltage must be applied to the cathode. Once the light is on, however, the 2.5 to 4.1 volts of initial cathode power is no longer needed to sustain lamp operation, and thus may be eliminated. There are several ways of accomplishing this, and these technologies are incorporated into ballasts known as 'hybrid ballasts' or 'cathode cutout ballasts'. They are available only for four-foot fluorescent versus standard or energy-efficient magnetic ballasts.

Solid State Electronic Ballasts

Electronic ballasts use integrated circuitry to convert the input electrical charge from 60 hertz to a range of 20,000 to 50,000 hertz. At such high frequencies the phosphors which coat the inside of the fluorescent lamps radiate light much more efficiently, thereby reducing the power needed to produce the same amount of light. The high frequencies of electronic ballasts also reduces the tendency of lights to flicker and ballasts to hum. Some of these ballasts have dimming capabilities. They have better maintenance of light output than other ballasts and provide good voltage and temperature regulation. Most have surge and thermal protection and high power factors.

Special Considerations

  • Ballasts are rated for operation at 77°. Cold weather conditions influence lamps and ballasts, decreasing light output. Below 30°, special lamps and ballasts are required.
  • Be sure to match the ballast chosen to the electrical requirements of the lamp for input voltages, power factor, operating temperatures and dimming capabilities.
  • Early versions of electronic ballasts caused some occasional minor problems, resulting in negative impressions among some users. Electronic ballasts on the market today are improved and generally perform well.
TYPICAL FLUORESCENT LAMP / BALLAST PERFORMANCE COMPARISONS
4 Foot / 2-Lamp Fixture
Type
Lamp
Watts/
Lamp
Operating
Ballast
Type
$/Fixture
Annual
Watts/
Fixture
Relative
% Light
Operating
Cost*
Output
Range**
F40T12
40
Standard (Base)
94
$28.20
BASE
F40T12
40
E.E. Magnetic
86
$25.80
92-100%
F40T12
40
Hybrid
72
$21.60
84-90%
F40T12
40
Electronic
72
$21.60
92-115%
F40T12
34
Standard
80
$424.00
85-90%
F40T12
34
E.E. Magnetic
70
$21.00
82-89%
F40T12
34
Hybrid
60
$18.40
76-80%
F40T12
34
Electronic
60
$18.00
82-90%

  * Based on $0.10 per kWh and 3,000 operating hours per year.
** Percentage of light resulting from the new efficient lighting system based on the existing standard system. These performance characteristics vary among lamp/ballast manufacturers.