Warehouse lighting ranges from a storeroom at an elementary school to a distribution center with hundreds of thousands of square feet. Lighting warehouses must consider traffic in storage areas and whether occupancy sensors can limit the time lights remain on after the stock person leaves. Advances in fluorescent light sources now gives us efficient lighting alternatives to metal halide lighting in storage areas.
Warehouse Lighting Projects
Warehouse lighting projects take into consideration the building, type of storage (whether rack or floor storage) and type of product being stored. The reasoning is large, bulky items require less light to make a selection decision than small items such as jewelry. Small items require more light and generally have the light source at relatively low levels. Bulk storage areas can have fixtures30 feet above the floor.
Metal halide fixtures used to be the only light source for high bay lighting but today fluorescent lighting is often the best lighting choice. Fluorescent T5/HO lamps can be used at heights of 30 feet or more yet will still provide excellent vertical footcandles for storage racks. The advantages of fluorescent light over metal halide are:
- Better lumen maintenance
- Better color rendering and
- Instant on when power is applied
All lighting sources "depreciate" over time. That means the lamp puts out less light as it ages and is therefore less efficient. Depreciation can be as high as 64% for metal halide lamps on magnetic ballasts. Newer, electronic ballasts can raise that value to 86% but even then is below the 95% lumen maintenance of fluorescent lamps.
There is a great deal of debate as to whether better color rendering is important when the task is selecting cardboard. Some would argue that the yellow light of sodium light sources is sufficient while other would argue the fact that when humans are involved color rendering and color temperature are important. Our recommendation for warehouse lighting is a color temperature of 5000 degrees and color rendering of 86.
The "Instant on" issue is based on the fact that most aisles in racked storage buildings are vacant 80% of the time but illuminated 100% of the time when metal halide with magnetic ballasts are used. Electric ballasts can dim metal halide fixtures to approximately 50% but because of restrike time it is not practical to turn them off. Linear fluorescent fixtures can be turned off until occupancy sensors detect the presence of the operator. By setting the sensor to delay turning off the fixture for at least 15 minutes after vacancy and using programmed start ballasts lamp life can be maintained at acceptable levels.
Warehouse Retrofit Projects
Energy efficiency can be improved by retrofitting old metal halide and T12/HO fluorescent fixtures with electronically ballasted fixtures. These projects are even more efficient when planned for installation at a point when group relamping is scheduled. In most cases fixtures can be replaced on a one-for-one basis which minimizes electrical work.
Where metal halide lighting is appropriate, replacing an old, 400-watt fixture with new technology may mean a 100 watt per fixture reduction. A savings of 100 watts per fixture could translate to $3,200 per fixture in a 24 x 7 operation. Replacing a metal halide fixture with a fluorescent fixture having occupancy sensors could save 2 or three times that amount.
Warehouse lighting retrofit projects begin with an energy audit to determine the amount of savings and return on investment. In some cases rebates and incentives may be available form the local utility.
For additional information call Service Lamp at 800-222-LAMP.