Linear Fluorescents
The most common linear fluorescent lighting systems consist of four foot lamps and corresponding ballast. For retrofits of existing fixtures, lamps must be compatible with the ballasts. Most new designs specify T8 lamps and electronic ballasts. T8 lamps cannot be run on ballasts designed for T12 lamps. In almost all applications, it is cost-effective to replace less efficient T12 lamps and magnetic ballasts with high efficiency T8 lamps and electronic ballasts. The only exception may be where the operational hours are extremely low.
Energy accounts for nearly 90 per cent of the lifecycle cost of owning and operating a fluorescent lighting system, while lamp costs account for about two percent. A T8/electronic ballast can save over 25 per cent when replacing T12 linear systems. The CRI for T8s ranges from 52 (for warm white lamps) to the mid-80s for lamps using rare-earth phosphors. Usually the higher a lamp's CRI, the higher its cost.
The newest family of linear fluorescent lamps is the T5 line of lamps, consisting of standard and high-output (HO) T5 lamps. As with many new technologies, the T5 line is often assumed to be more efficient than its predecessor. This is not necessarily the case. Generally, the standard T5 lamp and electronic ballast system have an efficacy comparable to a T8 lamp/electronic ballast system.
Because the T5 lamp is only available in metric dimensions and thus slightly shorter and a different socket size, it can't be easily or economically retrofitted into existing T8 or T12 fixtures.
A good rule of thumb is to install the most efficient equipment available that will deliver the amount and quality of light for the task. In most commercial lighting applications, the following guidelines apply:
- Use T8 lamps with electronic ballasts.
- Use four-foot lamps. This is the most common length and is the least expensive and easiest to buy, stock and handle.
- Use standard-output lamps. High-output (HO) and very-high-output (VHO) lamps make sense in niche applications, but they are more costly and less efficient than standard-output lamps. This is because their light output falls more rapidly over time, and they require heavy, oversized ballasts.
- Select lamps with a CRI of above 70 for workshop/warehouse use and 80 or above for office or equivalent environments. Lamps with a CRI above 85 are considerably more expensive, but may be worthwhile in retail or other colour-sensitive applications.
