Universal Lighting Technologies

Appendix B: Ambient Temperature and Atmospheric Conditions


Most fluorescent ballasts are designed for optimum performance (starting dependability and light output) at an ambient temperature of 70º F to 80º F, which in still air will provide a lamp wall temperature of 100º F to 120º F. Any variation will affect performance as noted in the following sections.

Low Ambient Temperature

All ballasts have a limitation as to their ability to start lamps at low temperature. Always check the ballast and lamp manufacturers’ recommended “minimum starting temperature” if low ambient temperature is a suspected problem.

Low ambient temperature is not the sole factor in determining poor starting conditions. Voltage, humidity, drafts, polarity, dirt and spacing between lamps and starting aid may also influence starting dependability.

Universal Lighting Technologies produces a number of ballasts which provide reliable starting down to –20º F.

Drafts and moving cold air may cause the lamp to flicker. To correct problems caused by cold and drafts, the use of enclosed fixtures is recommended. This allows heat generated by the lamps and ballasts to be retained within the fixture, raising the bulb wall temperature to a level which will maintain proper light output. Bear in mind that excessive lamp shielding may also cause lamp and ballast overheating in the summertime.


Many fluorescent lamp ballasts are designed for use only in dry environments, protected from moisture and weather. If ballasts are to be used under circumstances exposing them directly to weather, moisture or other atmospheric conditions, special fixtures or ballasts designed for such environments must be used.

All Universal Lighting Technologies encased fluorescent lamp ballasts meet UL TYPE 1 requirements and can be used in outdoor fixtures or in fixtures for wet or damp locations.

Moisture or humidity, combined with dirty lamps, can cause hard starting. Keeping the fixture and lamps clean will alleviate most moisture-related problems.

High Ambient Temperature

To meet the requirements of Underwriters Laboratories, Inc., and assure maximum service life, the fixture and application must be designed to prevent any part of the ballast case from exceeding 90º C. Operation above this limit will shorten ballast life, can possibly damage adjacent materials or thermally protected ballasts, and cause cycling (on and off) of the lamps.

For additional information regarding heat, its effect on ballasts and possible solutions to high temperature related problems, refer to Appendix F.