Universal Lighting Technologies

Appendix E: Line Voltage

Operating Line Voltage Limits

To receive the full benefits of rated lamp light output and to prolong ballast life, it is essential that the voltage supplied to an installation be maintained within the prescribed limits.

Ballast Type Limits
Reactor (R) or high reactance autotransformer (HX) ± 5%
Constant wattage autotransformer (CWA) or ISO Reg ± 10%


Low voltage has no damaging effect on the ballast. It could, however, have an adverse effect on lamp performance and starting dependabilty.

Subjecting a ballast to excessive voltage for an extended period of time results in the deterioration of the coil insulation. The insulation breakdown will cause early ballast failure.


Polarity refers to the proper connection of ballast lead wires to line wires. To aid in correct installation, Universal Lighting Technologies ballast leads are color-coded for ease of identification. The white or yellow ballast lead is to be connected to the neutral or common (grounded), and the black ballast lead always to the line, phase a,b, or c on a 3-phase, 4-wire system (typically 120 or 277 volts). When connected to the 3-phase ungrounded system (typically 208 or 480 volts), the black goes to one phase and the white or yellow lead goes to the second line phase-i.e., a-b, b-c, or c-a.


All ballasts and capacitors or starters in metallic casings must always be grounded. Ballasts and components may be grounded to the fixture or otherwise connected to the ground. It is hazardous and possibly fatal for a human to make contact with an ungrounded fixture, ballast or other electrical component while it is in operation.