Temperature Measurement on Operating Surface Mounted Lighting Fixtures

摘要

Potentially hazardous temperatures may result from adding thermal insulation in the attic above surface mounted incandescent lighting fixtures and/or operating these fixtures with lamps of higher wattage than specified. This study was concerned with the range of temperatures generated (1) within the fixture, (2) within the electric junction box associated with the fixture and (3) on the adjoining ceiling and attic surfaces. Test results indicate that the addition of minimal insulation (equivalent to R11) over a surface mounted lighting fixture which contains two or more rated lamps, is likely to cause normal household branch circuit supply wiring associated with the fixture to operate above its specified 60C temperature rating. Overlamping (using lamps of higher wattage than specified for the fixture) and/or additional load current flowing through the branch circuit wire will cause even higher supply wire temperatures. With all three conditions present (i.e., insulation over the fixture, overlamping, and an additional 15 ampere load current flowing through the supply wire), the tests indicate that the temperature of associated branch circuit wiring will exceed 80C for a one lamp fixture and 100C for fixtures with two or more lamps.