Universal Lighting Technologies

Appendix D: Line Voltage

Line Voltage Limits

To receive the full benefits of rated lamp output and to prolong ballast life, it is essential that voltage supplied to an installation be maintained within limits prescribed for each circuit. These limits are listed below.

Voltage Range
Nominal Voltage   Minimum Maximum  
120   110 125  
220   205 232  
240   225 250  
277   255 290  
347   315 364  
480   450 505  
600   570 630  


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

Low voltage has no damaging effect on the ballast. However, lamps may not start with desired reliability and early lamp failure could result.


Polarity refers to the proper connection of ballast lead wires to line wires. To aid you in making a correct installation, Universal Lighting Technologies ballast leads are color-coded for easy identification. The white ballast lead is to be connected to the neutral (grounded) and the black lead always to the phase (“hot”) line wire. For systems with neither of the line wires at ground potential, specially designed ballasts are required. A change in polarity may result in the voltage from lead to ground exceeding limits specified by Underwriters Laboratories, Inc. In some types of ballasts, a change in polarity may decrease voltage from lead to ground, thereby impeding the starting dependability of the ballast.

Power Factor

Power factor expresses how efficiently the lighting system utilizes electric current. It is the ratio of input watts to the input volt amperes. High power factor ballasts are those with a minimum power factor of 90% or greater. Low power factor ballasts generally draw twice the current of a high power factor ballast designed for the same application. Many utility companies charge a penalty should the power factor of an installation fall below a prescribed level.

% Power Factor =   
Input Watts
Line Current x Line Voltage
   x 100