![]() ![]() Volume 9 Issue 2
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July 2006
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How is performance affected by ambient temperature? (cont'd)Short-term thermal effects (cont'd)The five high-wattage compact fluorescent lamps (HW-CFLs) tested by NLPIP were retrofitted in a luminaire designed for metal halide (MH) lamps. NLPIP then measured thermal conditions, electric power, and light output (see Appendix A: Thermal testing of HW-CFLs and Appendix B: Power and light output of HW-CFLs for details). Figure 11 shows that when HW-CFL samples were operated in open air, lamp temperature was the lowest. When each HW-CFL was installed in either the aluminum reflector or prismatic refractor, lamp temperature increased. When each reflector was fully enclosed, the temperature increased further. Data from an example of a MH lamp is also included in Figure 11 for reference.
NLPIP demonstrated that all samples tested had reduced light output when the luminaire was fully enclosed. Figure 12 shows the light output reductions of the HW-CFL samples due to elevated temperatures when the two luminaire types were fully enclosed. Enclosure had a greater relative impact on light output with the aluminum reflector than with the prismatic refractor. However, these data are reported in relative terms; readers should not assume that illuminances will be lower when retrofitting HW-CFLs into aluminum compared to prismatic luminaires.
Electric power is also affected by thermal conditions. As shown in Figure 9, operating power varies as temperature varies. As temperature increases beyond the optimal temperature, power, and subsequently efficacy, can be expected to decrease. Figure 13 shows electric power of five HW-CFLs in luminaires (see Appendix A: Thermal testing of HW-CFLs for testing methodology). The HW-CFL power was reduced by 4.5% to 14.5% as temperature increased due to operation inside an enclosed luminaire (Figure 14).
Although light output of a HW-CFL decreases when operated at elevated temperatures, power also decreases, thus efficacy may not necessarily decrease. NLPIP estimates that efficacy of these samples changed during thermal testing by -7.6% to +2.9% |
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