Basic Basic Ballast Information for 4 Ft. Fluorescent Lamps

The term "ballast" used in fluorescent lighting applies to the device that controls the lamp current (milliamp) at the proper operating parameter for the lamp, provides proper open circuit voltage to start the lamp reliably without excessively damaging the cathodes, and provides the proper cathode heating voltage (3.6 - 1.2 volts) for rapid start lamps

Ballasts for four-foot fluorescent lamps are available in the following three generic categories: Magnetic -- energy efficient (core-coil capacitor), Electronic - solid state high frequency, Hybrid -- magnetic with electronic cathode cutout.

Energy efficient magnetic ballasts (required by law since 1988) are 10 to 12 percent more efficient than older- types because of the higher performance materials used in their manufacture. They have lower maintenance costs, longer life (three year warranty) and cooler operation than their predecessors. They operate the lamps at the nominal 430 ma. and allow the lamps to produce greater than 92.5% of rated lumens. They consume eight to 10 watts when operating with the lamp in the circuit. The ballast will consume about four watts when the lamps are removed although the ballast is still energized.

Electronic ballasts start and regulate fluorescent lamps with the use of electronic components. They operate at frequencies of 2OkHz - 4OkHz and provide the following advantages: Higher lamp efficacy, Lower power consumption, Quiet operation, Cooler operation, High power factor, Less weight, Longer lamp life Fluorescent lamps are more efficient at higher frequencies. Therefore, 40-watt T12 lamps operate at 34 watts when operated on an electronic ballast. A two-lamp ballast system consumes 68 - 71 watts. At these lower wattage's, the lamps provide light output close to rated lumens at 60Hz.

Hybrid ballasts (cathode or heater cutoff) are a combination of electromagnetic technology electronic components. This ballast contains an electronic switch that cuts off the power to the cathode after the lamps have started to light. By de-energizing the cathode, energy is reduced by an additional 2 - 2.5 watts per F40 lamp. Generally, these ballasts have a life expectancy of 25 years. Hybrid ballasts are not designed for operation with T8 lamps.

The following chart should be helpful in determining power consumption of various systems and fixture combinations:

Wattage* of Two-Lamp Fluorescent Systems
Two Lamp System
EE
Magnetic
Electronic Hybrid
-
Type of Fixture
Enclosed
Open
Enclosed
Open
Enclosed
Open
F40 T-12 40 Watt
79
82
68
71
76
80
F40 T-12 34 Watt
68
74
61
64
65
68
F40 T-10 40 Watt
80
83
70
74
78
81
F32 T-8 Rapid Start
69
75
57
62
N/A
N/A
F32 T-8 Instant Start
70
73
54
56
N/A
N/A

Enclosed fixture wattage based on ANSI C82.2

*Values may vary +/- 1 watt depending on ballast manufacturer.