Answers to the following questions can help you decide whether power reducer technology is right for a given application.
Would another solution be more cost-effective? Although power reducers may be a viable option in a given situation, they are usually not the only one. Other ways to reduce the energy consumption in a magnetically ballasted T12 lighting system—one of the primary targets for power reducers—include the following:
- Retrofits with electronic ballasts and T8 lamps
- Reflector, lens, or fixture retrofits combined with delamping
- Upgrades to low-ballast-factor or cathode cutout ballasts
- Installation of dimming electronic ballasts
To choose the best option, determine the possible savings and the payback period. Table 1 shows four possible upgrades to a bank of fluorescent lamps initially equipped with T12 lamps and magnetic ballasts. The quickest payback comes with an energy-saving lamp retrofit, but the two T8/electronic ballast options offer the greatest life-cycle energy savings. Simple payback for the T8 option with normal ballast factor is faster than that for the power-reducer option and results in slightly greater light output. The T8 option also improves the color quality of the light provided.
Table 1: Power reducers and fluorescent lighting
In this comparison of payback periods of four retrofit options for a school building, the power reducer has the longest simple payback period at 4.2 years. However, the two options with the shortest payback periods result in less light output than would result from use of a power reducer. T8 lamps with normal-ballast-factor electronic ballasts provide light levels closest to the baseline levels and still feature a 3.5-year payback.
For HID lighting systems, one alternative to lighting-circuit power reducers is a high-intensity fluorescent retrofit. In Table 2 we compare the addition of a power reducer to a metal halide lighting system with the installation of a high-intensity fluorescent system.
Table 2: Power reducers and HID lighting
For this hypothetical comparison, we assumed that the power reducer would cut both energy use and light levels by 20 percent. Power reducers can provide a fairly quick payback in a facility with high-intensity discharge (HID) lighting, but paybacks may be faster and energy savings greater with a high-intensity fluorescent retrofit.
Although both systems pay for themselves in less than three years, the fluorescent option saves more energy and provides more light. In addition, the fluorescent system provides a number of other benefits, including better lighting color, faster start-up and restart time, and less glare.
Will illumination levels fall below requirements? Do not install power reducers if users will not be able to work as efficiently or as safely in the reduced light levels that will result.
Is a boost in lighting quality required? Power reducers will not improve the lighting quality in a space. If that’s what you are after, other measures will be more effective, such as the use of light sources with better color quality (higher color rendering indexes) than the existing lamps, or the use of fixtures, such as direct or indirect luminaires, that reduce glare.
How well will the technology work with your particular lamps and ballasts? Power reducers aren’t compatible with all types of ballasts, although some products are more versatile than others. In fluorescent lighting, some products work only with magnetic ballasts and others work with both magnetic and a few types of electronic ballasts, but none works with active front-end electronic ballasts. The active front-end ballasts, which compensate for fluctuations in incoming voltage and would therefore defeat the action of a power reducer, represent a growing share of the market for fluorescent electronic ballasts. It’s not always easy to tell if a ballast features an active front end, but most often multiple-voltage ballasts, universal-voltage ballasts, and ballasts with total harmonic distortion of less than 10 percent are made with active front ends.
For HID lighting, power reducers are compatible with both reactor-type ballasts and constant wattage autotransformer ballasts, although the savings potential is higher with reactor-type ballasts. So far, none of the power reducer products works with electronic HID ballasts, which, though rare, are becoming more common.
Will the use of this technology void lamp and ballast warranties? Potential users of power reducers should check with lamp and ballast manufacturers to make sure their equipment is compatible with a particular power reducer and to see if use will void the lamp or ballast warranties. Conversely, the power reducer manufacturer may provide its own warranty.
If a power reducer passes each of these “tests,” it may indeed be the best choice for managing energy use and responding to load curtailment signals. If you have chosen to install power reducers, then follow these guidelines:
- Pick a product that can interface with photosensors, time clocks, and other energy-management systems. Some products are available in both autotransformer and electronic power-reducer categories that can interface with other energy-saving controls.
- When specifying a power reducer, make sure that it will not delay lamp starting or cause visible flicker.