Recessed light fixture test facility

Abstract

Test results are presented for the operation of recessed light fixtures in contact with loose fill cellulose insulation. Nine recessed fixtures were operated at different power levels in attic sections in which loose fill cellulose was purposely misapplied. Cellulose insulation was introduced into the ceiling section by pouring to depths of up to nine inches. Maximum steady state temperatures were recorded for 485 combinations of the variables insulation depth, fixture power, and attic temperature. Results are included for operation of fixtures in the absence of cellulose and with barriers to provide needed clearance between the cellulose insulation and the powered fixtures. Observed temperatures on the electrical power cable attached to a fixture and ceiling joists adjacent to powered fixtures are reported. Examination of the data shows excess operating temperatures are encountered when powered fixtures are covered by three inches of loose fill insulation. Dangerous temperatures resulting in fires in some cases were recorded when covered fixtures were operated at above rated power levels. A preliminary analysis indicates that ceiling side heat transfer accounts for 85 to 90% of the heat dissipation from powered fixtures covered by three inches of loose fill cellulosic insulation.

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