Group Relamping

Effective Lighting Management: Group Relamping

Group relamping offers significant savings in time and labor costs over spot replacing failed lamps. Regularly scheduled maintenance based on projected lamp life and lumen depreciation keeps a lighting system functioning at its maximum by replacing all lamps at their economic life.

When you think that you have cut operating costs to the max, let us show you how you can do more with less. According to the U.S. Department of Energy (DOE), lighting can represent over 38% of the average commercial building’s electric bill.

Take it from our customers, a regularly scheduled group relamp of your building greatly reduces your material and labor costs. Many lamp manufacturers offer a warranty for group relamp projects that provide you with the product warranty of up to two years. Industrial Light and Power has established a relationship with Sylvania Lighting to ensure a smooth, hassle-free warranty program for you. And, we maintain a database of information for our customers, so your product information is easily tracked. Industrial Light and Power also retrofits complete lighting systems to reduce daily electrical costs while at the same time delivering a safer, better lit, more productive work environment.

Energy-saving lighting solutions are available that reduce your costs while maintaining or improving lighting quality. The Energy Savings Cost Council reports that these projects have an average payback of 2.2 years and a 45% return on investment. Group relamping is a process that saves money when fluorescent, high-pressure sodium or metal halide lighting is used. All lamps in a group are replaced at the same time rather than one at a time on failure. Using group relamping has been found to reduce relamping costs by 50%. Whether your staff does group relamping or you ask Service Lamp to provide the service, group relamping is a cost-effective way to keep your lighting in top shape.


Why Group Relamping Works:

You know from experience that incandescent lamps fail at random. Service life for bulbs is an average so half the bulbs will fail before the service life stated on the package. Incandescent lamps can fail at random and far short of the average because of the filament. Physical shock or vibration for example will cause a lamp failure. Power spikes can also dramatically shorten the bulbs life.

High intensity discharge lamps and fluorescent lamps, do not use a filament to generate light. The processes used to generate light are predictable such that most lamps will need to be replaced near the end of their rated life. Ballasted lamps are perfect candidates for group relamping.

The predictability of this class of lamps also enables us to project lumen depreciation. Lumen depreciation simply means that an old lamp is not as bright as a new lamp. Over time the business still pays 100% for electricity but may only get 30% of the light output from a depreciated metal halide lamp. Lower light levels due to lumen depreciation or dirt accumulating on the lamp or fixture are important considerations for group relamping.

Another consideration for group relamping is the effort required to change a lamp. This type of lighting is generally high above the floor. On the retail sales floor merchandise needs to be moved to change a lamp. Changing bulbs during work hours in offices or production areas means disrupting work flow. Service Lamp can arrange for group relamping to take place overnight with zero production or sales lost.

How Group Relamping Works:

Group relamping means replacing all light bulbs at one time completely or in an area of the a store or warehouse. The advantage of group relamping is about a 50% savings in labor costs when compared to replacing lamps on failure. There are other tasks performed during group relamping that are common sense aspects of facility management.

The other advantage of group relamping is that it is easier to meet storage and handling requirements for ballasts and spent lamps containing mercury. Lighting products replaced during the group relamping process are removed by our service or can be shipped to the recycler immediate after removal. Spot replacement generally accumulates spent lighting product over a long time.

Industrial Light and Power can meet your group relamping needs by providing quality lighting products for your maintenance department or a complete package including labor. Qualified technicians and electricians will be dispatched to your property with all the materials necessary to complete the job. Typically an entire property can be done overnight and ready to open the next morning.



1) Optimum Light Output:
Light levels are at their peak when your lighting installation is new. Most traditional metal halide lamps decrease in light output to 40% of initial light output by the end of rated life. A number of factors may accelerate this reduction in efficacy (lumens per watt). Group relamping at economic life keeps the light levels from dropping significantly. It also provides an opportunity to remove dirt accumulation in the luminaires. Cleaning during group relamping saves time and helps maintain optimum light levels. A cleaner, well-lit environment increases safety and security, can contribute to higher worker productivity and creates a better impression on visitors.

2) Aesthetic Quality:
The quality of light changes over economic life, shifting 200K to 300K in color. In the last 25% of rated life it may accelerate, shifting 500K to 600K. This causes old lamps to appear blue or pink especially when compared to new lamps. All the lamps in an area will generally change color together; so the color shift of the lamps will be most noticeable during spot relamping.

3) Optimum Energy Efficiency:
While the light output of traditional metal halide lamps decreases over life, they still consume the same (or sometimes more) electricity. Since energy is the largest cost of lighting, group relamping prevents almost half of the energy from being wasted by under-performing lamps. For example, a 400 watt traditional metal halide lamp may consume $800 of electricity over rated life. After 60% of rated life, about $320 is wasted on lamps providing less than mean lumens. Spot relamping wastes energy dollars. The cost of a new lamp and the labor to install it as part of group relamping is generally less than 5% of the total energy cost.

4) Cost Effective Replacement:
Group relamping, as a planned maintenance program, reduces downtime and labor costs. Spot relamping often takes an employee away from regular duties just to replace a burned out lamp. This inconvenience grows as lamp failures increase towards the end of rated life. Group relamping not only eliminates wasted labor and workday disruptions, it allows for scheduling during normal shutdown periods.

Group relamping at economic life is a practical way to reduce energy and maintenance costs, as well as sustain workers’ visual acuity with a bright workplace environment.

Lumen depreciation, color shift over life and cost reduction are the main reasons that a user should consider a group relamping program. When a lighting installation is new, the light level is high and the quality of the light is excellent. Over life, lamps suffer a decrease in efficacy (lumens per watt) caused by both the loss of the light producing chemicals within the arc tube and darkening of the inner walls of standard arc tubes. Most metal halide lamps will decrease to around 60% of initial rated light output at about half of rated life.

In standard metal halide technology, not only is there a decrease in the amount of light generated over life, but the quality of the light also changes. The color of a metal halide lamp is made up of hundreds of spectral line emissions from the chemicals within the arc tube. This plot of the lines of color the lamp emits is called its spectral distribution. It is this collection of colored lines that our eye interprets as a “white” light.

You might remember holding up a prism to the sunlight and seeing the rainbow of colors produced. The prism is able to break down the sunlight into all of its many spectral components. Even though sunlight has all of these component spectral lines, our eyes, together with our brains, interpret the combination of all these colors as white sunlight. The same phenomenon is happening when you look at the light produced by a metal halide lamp.

One difference between sunlight and the light from a metal halide lamp is that the sun produces the same quality of light at all times. The differences we see in sunlight are caused by the effects of earth’s atmosphere, not by changes in the sunlight. The metal halide spectral distribution, however, is not as stable as the sun’s. Its spectral output comes from mercury and metal iodides present in the arc. As the chemicals are lost to the arc through reactions, the proportions of their contribution to the spectrum change. Our eye interprets these changes in spectral distribution as changes in lamp color.

Generally, a metal halide lamp will shift in color by about 200 to 300K during its economic life. If all the lamps in an installation are operated in the same fixture type and burning orientation, they will generally change color in the same direction and amount during economic life. Therefore, the color shift of the lamps will not be very noticeable. The problem arises when you spot relamp after economic life. By then a lamp may have shifted 600K or more causing lamps to appear bluish, pinkish, or greenish. With spot relamping, a new, bright white, initial lumen output lamp is installed in a field of lumen depreciated and slightly color shifted lamps. The human eye is a wonderful device for comparing color and it, of course, is able to easily discern that the new lamp is both brighter and a different color than the old lamps. If you multiply this scenario over a series of spot relampings, you can see why eventually a metal halide lighting installation can have quite a non-uniform look.

The answer to this problem is a group relamping program in which the user relamps the entire installation at one time, usually sometime between 60% and 70% of rated life. This plan has a number of advantages:

Cost Effectiveness:

Group relamping greatly reduces spot relamping labor costs because all lamps are replaced before they reach the point in life where failures are accelerating. In addition, the cost of energy is by far the largest portion of maintaining a lighting system. If lamps are not group relamped, almost half of this energy will be wasted on lamps that are performing below their designed level. As an example, an average 400 watt metal halide lamp consumes $800 of energy over its rated life. About $320 of these dollars are wasted on lamps not providing optimum performance. With group relamping, a new lamp and the labor to install it is generally less than 5% of the total energy cost. Group relamping also saves downtime because it can be scheduled over a weekend or shutdown period.


When lamps are of similar light output and color, a lighting installation looks better. Shopping centers, retail stores and even gas stations with canopies are retail spaces that are trying to attract customers. The quality of the lighting says much about the store and the merchandise. Group relamping maintains the quality of light in a space infinitely better than spot relamping.

Improved Light Levels:

An installation that is properly group relamped will have better maintained light levels than one which is not. Higher light levels have been associated with increased safety, higher productivity and an increased sense of security. Since it costs the same amount of energy to run a fully lumen depreciated lamp as a new lamp of the same wattage, doesn’t it make sense to install the higher lumen output lamp in the socket?

Group relamping from Industrial Light and Power….Illuminating your world…….

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