Universal Lighting Technologies

Appendix G: Ballast Overheating

A ballast, like any other electrical device, generates heat during normal operation. Planning for maximum heat dissipation with proper fixture design, installation planning and ballast selection will minimize the possibility of a heat-related problem. Excessive temperature will have an adverse effect on ballast life.

Normal Temperature Limits

Encased & Potted
Maximum case temperature: 90°C

Postline Ballasts
Maximum case temperature: 90°C

Weatherproof Ballasts
Maximum case temperature: 90°C

Core & Coil Ballasts
Insulation: H 180°C
Maximum coil temperature: 165°C
(measured by change of resistance method)

Potted Core & Coil Ballasts
Insulation: Class 180
Maximum coil temperature: 165°C
(measured by change of resistance method)

Indoor Encased
Maximum case temperature: 90°C

Encased & Potted ballasts are equipped with an automatic-resetting thermal protection device as a built-in standard internal feature.

The resetting thermal protector functions as a thermostat which will open and temporarily deactivate the ballast when it exceeds the permissible temperature. The ballast will continue to cycle until the cause of overheating is eliminated. If the ballast if defective, it must be replaced. If the cause is external, the ballast will resume normal operation after abnormal conditions are eliminated. Possible external causes include insulation around the fixture or poor air circulation around the fixture.

Whenever a ballast with thermal protection is used, it is imperative that the fixture/ballast-lamp combination be heat-tested under actual or simulated installation conditions to ensure that the ballast will not cycle.

Other ballast types may be available with thermal protection as an option. If required, call Universal Lighting Technologies’ Technical Engineering Services at 1-800-762-4837 for availability and ordering information.

Even when a ballast is protected against excessive operating temperature, it is still subject to the normal parameters for ballast life. In the proper application and for normal ballast life, maximum coil temperature of the ballast should not exceed the rating of the insulation system. A temperature rise of 10°C can result in a 50% reduction in ballast life. This elevated temperature could occur without tripping the thermal protector.

Note: Special attention should be given to remote mounting of indoor encased ballasts. They should be mounted at least 12” apart to prevent over-heating.