Lighting Research Center Lighting Research Center
    Volume 6 Issue 1
July 2002    
Does a two-lamp luminaire using T5 HO lamps produce as much light as a three-lamp luminaire using T8 lamps?

In most cases, a two-lamp luminaire using T5 high output (T5 HO) lamps produces more light than a three-lamp luminaire using T8 lamps. Table 11-1 compares nominal system performance between T5 HO and T8 direct/indirect luminaires—a two-lamp luminaire using T5 HO lamps and a three-lamp luminaire using T8 lamps. Table 11-1 suggests that the initial system lumen output from the two-lamp luminaire using T5 HO lamps is higher than the three-lamp luminaire using T8 lamps. This difference means that a two-lamp luminaire using T5 HO lamps can replace a three-lamp luminaire using T8 lamps. This calculation also shows, however, that the two-lamp luminaire using T5 HO lamps may be less efficacious than the three-lamp luminaire using T8 lamps if lamp-ballast system efficacy is considered. An absolute measurement appears in the (CASE STUDY Case Study )

Table 11-1. Comparison Between a Two-Lamp Luminaire Using T5 HO Lamps and a Three-Lamp Luminaire Using T8 lamps

Ballast No. Lamp Combination
and Type
Lamp Power
(W)
Ballast Factor Input Power
(W)
Initial Light Output
(lm)
Initial System Efficacy
(lm/W)
Temperature
(°C)

1 Two-T5 HO 108 1.0 120 8,900 74 25

10,000 83 35

2 Three-T8 96 0.87 80 7,699 96 25


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