Planned Maintenance Techniques

When a new retrofit lighting system is being designed, a well-planned
maintenance schedule can aid in reducing costs and energy usage.

GROUP RELAMPING

When all of the lamps in a system are replaced at one time after a fixed interval, it is referred to as group relamping. The fixed interval is called the economic group relamping interval. Benefits of group relamping are reducing the cost in the operations of the lighting system and improving illluminance. In considering the redesign of a lighting system, if group relamping is deemed to be economical, less over design will need to be considered. This will lead toward a savings in the initial cost of the design and the operating and maintenance costs associated with the new system.

Group relamping savings are the result of labor cost savings. The cost to replace one lamp one at a time as they fail is usually less. However, it makes more sense to replace all the lamps if the labor savings exceed the value of the used lamps even though there is still life left in some of the lamps.

Group relamping should be considered if:

The labor cost of spot-replacing one lamp less the cost of group replacing one lamp exceeds the cost of one new lamp.

There are analysis techniques available to aid in determining the economic group relamping interval. These include the mortality rates of the lamp, labor rates, and cost and depreciation rate of the lamp. At 70% to 80% of the rated life it has been found to be the most economical time to group relamp. This also is at the time when the cost per lumen becomes uneconomical to continue operating the lamps. The cost of replacing spot failures should also be taken into account in making the final calculation so that optimum appearance and quality of light are kept.

Thus scheduled intervals of maintenance of the lighting system can be expanded to include installing other component parts for optimizing the system and providing energy efficient replacements.

Additional information may be found in the IESNA Lighting Handbook.