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Detecting Defective Lighting Ballasts

Lighting ballast failure may present more than an inconvenience; in some cases, it may present a fire hazard. Under the right conditions, an infrared imager may be used to detect overheated ballasts.

Lighting ballasts are dry-type transformers commonly found within fluorescent and HID light fixtures. Because ballasts are usually direct-mounted to the interior of the fixture casing, surfaces adjacent to ballasts frequently operate at nearly the same temperature. In the case of fluorescent fixtures, ballasts are usually in direct contact with the top surface of the fixture.

Properly functioning ballasts will operate up to several degrees above ambient air temperature. Defects such as short circuits or defective wiring can cause a ballast to significantly overheat. If ballast temperatures are sufficiently high, a fire may result.

By using an infrared imager to inspect fixture surfaces adjacent to ballasts, it is possible to rapidly detect evidence of overheated ballasts. When applying thermal imaging to installed fixtures, keep the following in mind:

• Ascertain how construction of subject fixtures will affect observed temperatures
• Plan inspection to afford clear line-of-sight to fixture surface
• Ensure fixtures are properly lamped and under load during inspection
• Allow sufficient time for fixtures to achieve thermal equilibrium
• Investigate excessively warm fixtures for cause

Infrared inspection of electrical distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer^® training course. For information on thermographer training or to obtain a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, visit us online at www.infraspection.com or call us at 609-239-4788.