Magnetic dimming systems first introduced in the 1970s were cumbersome, noisy, and inefficient. And electronic fluorescent dimming ballasts produced in the late 1980s were prohibitively expensive and often excluded from Demand Side Management program rebates. However, current systems offer a viable alternative which, in turn, has made daylight harvesting and energy management more attractive.
Many facilities install skylights or large window walls with photocells and dimming ballasts to reduce lamps when natural light is available. Using a complete system, including T8 lamps, electronic fluorescent dimming ballasts, and a control mechanism, can result in significant energy savings of 55 to 80 percent.
A look at the system features
Fluorescent electronic dimming ballasts can be connected to standard automatic wall switches or relays, photocells, and/or occupancy sensors, and can be integrated into building energy management systems that control lighting, heating, and air conditioning. In addition to dimming the ballasts, the combination of daylight harvesting, occupancy sensors, load scheduling, and load shedding help reduce energy consumption.
Daylight harvesting uses photocells or light sensors to take advantage of “free” sunlight and reduce the cost of supporting light through dimming. Photocells measure the light level in an area, ensuring that an adequate number of foot-candles are present. If daylight falls below the required level, the lamp/ballast system kicks in to compensate with artificial light. Typical collection applications are in large facilities with walls of windows and in commercial and institutional buildings that use skylights.
Load schedules are used to determine the light levels needed in building spaces to minimize energy consumption. For example, a facilities manager might recognize that the conference room is used every day from 10 am to 11 am The lighting system could be programmed to dim the lights during non-occupied hours.
Load shedding is used to determine appropriate light levels while minimizing power consumption and reducing operating costs during peak hours. Utility companies often charge premiums for energy use during these times. Load shedding typically works with daylight harvesting using daylight and lighting dimming as a system, therefore power “off”. Facilities that operate on set schedules can reduce energy consumption with charging schedules. Maintaining proper light levels and dimming the lighting system where appropriate also support facility energy management.
Maintenance is easy on these systems. Most fluorescent electronic dimming ballasts now include circuitry that monitors the cathode voltage of the lamp, protecting lamp life and protecting the ballast against improper installation. The ballasts also turn lamps on at any preset level, so the ballast no longer has to be at 100 percent to start the lamp.
Dimming models maintain light levels for the life of a system. Normal systems levels (at full capacity) tend to decrease over time due to depreciation of the lamp lumen and the accumulation of dirt and dust. Since dimming ballasts used in conjunction with photoeyes are often not fully operational, the system can automatically adjust to maintain light levels even with lamp lumen depreciation and dirt buildup.
the right approach
The main types of fluorescent dimming systems are continuous and light level switching. Continuous allows the user to set the lighting to any desired level. Light level switching, on the other hand, uses preset levels and standard wall switches that allow the user to manually adjust the dimming to preset levels or wire the switch with a photocell that will automatically adjust the light to set preset levels.
Continuous systems maintain full range attenuation from 100 to five percent. The user can manually set the light level to a preferred outlet. Typical applications for continuous systems are conference rooms that require darkness for presentations, but must also provide enough light for writing. They provide a cost-effective solution for both new construction and renovation, with energy savings of up to 80 percent.
Light level change uses preset levels. This system can be operated with two regular wall switches instead of installing a low voltage dimmer control. Two types are available: 100 to 50 percent; and 100 to 60 to 30 percent. Light level switching is an ideal alternative to internal/external switching and low voltage dimming controls.
Better aesthetics are achieved because all lamps in the fixture dim to the fixed light level, compared to the internal/external switch turning off one or two lamps. Both new construction and renovations benefit from the light level change with savings of up to 55 percent.
Fluorescent dimming systems provide creative energy-efficient options for lighting in commercial, institutional, and even industrial facilities. All buildings, no matter how small, can benefit from the incorporation of a system of this type. With energy concerns becoming more prominent, realized energy saving dimming systems make them an ideal lighting application solution.