Lighting maintenance can play a part in a lighting upgrade project in three ways. First, proper maintenance can increase average light levels, potentially increasing energy savings in a retrofit. Second, it ensures the new lamps continue to be installed over time without “snap back”—accidental reversion back to the old lamp type that fits the same socket. And third, proper equipment selection can result in energy savings and easier maintenance for the customer.
For many applications, proper maintenance is planned maintenance, as recognized by IES RP-36-03, “Planned Indoor Lighting Maintenance,” primarily involving scheduled group relamping and fixture cleaning.
Group relamping entails replacing all lamps in a lighting system on a scheduled basis, often with spot relamping in between the group relamping cycles. Why throw away perfectly good lamps? Group relamping can economize on labor costs, improve space appearance and minimize disruptions caused by continuous spot relamping.
Here’s a rule of thumb: Group relamping is economical if the labor cost to spot relamp one lamp minus the labor cost to group relamp one lamp is greater than the cost of a new lamp—i.e., if the labor savings more than offsets the higher lamp cost.
In addition, group relamping for fluorescents typically is recommended at 60–70 percent of rated lamp life. In some cases, this can be rounded for simple scheduling—e.g., every five years. Extended-life linear fluorescents, programmed-start ballasts and LED equipment can significantly extend light source life and, with it, appropriate group relamping intervals when such products are used.
LEDs in general lighting applications have begun to change the rules of maintenance. First, lamp life is not rated as the point at which half of a large group of lamps is expected to fail. It is rated as the point at which 70 percent lumen maintenance (30 percent reduction in light output) is realized—about 50,000 hours for many of today’s LED sources or more than a decade of operation in a typical office building. Second, LED devices don’t fail on a mortality curve as with other light sources, virtually eliminating spot relamping. While an LED will last a long time—unless the LED fixture has an alarm or automatic shutoff mechanism at 70 percent lumen maintenance, and today’s products generally don’t—the LED will continue operating and producing less and less light while light levels continue to decline, which may cause a problem in spaces with critical visual tasks.
Maintenance can be economized further by combining group relamping operations with fixture cleaning, another staple of proper maintenance, to remove dirt and dust that blocks light from exiting the light fixture and potentially altering its distribution.
Here’s another rule of thumb: Fixture cleaning begins to become economical when the cost of lost light output from the fixture due to dirt and dust equals the cost of cleaning the fixture. After that point, it will cost more to operate the fixture wastefully than clean it.
Lighting upgrade strategy?
Planned maintenance can provide more flexibility to potential leverage reductions in maintained light levels into additional energy savings. For example, if planned maintenance raises maintained light levels from 50 to 55 foot-candles on the task in an open office, this provides additional “fat” for the lighting upgrade—light output that can be sacrificed to press energy savings.
Planned maintenance also can help prevent snap back. The policy should identify the lamp schedule to prevent gradual substitution of lamp types, which can jeopardize the intent of an original lighting design or upgrade. Suppose a lighting upgrade includes a switch from fluorescent T12 to 30W T8 lamps to save energy. Since the 30W and the standard 32W T8 lamps look the same and fit the same sockets, the maintenance department might begin replacing the 30W lamps with 32W lamps as they fail, disrupting uniformity and eroding energy savings. Similarly, the upgrade lamp and ballast schedule should be as simple and contain as few lamp and ballast types as possible.
Finally, maintenance provides another reason to upgrade some lighting types beyond the energy-savings argument. For example, probe-start metal halide lamps experience color shift over time, incandescent lamps provide short service life, high-pressure sodium systems cycle, etc. Replacing older systems with appropriate alternatives will save energy and make maintenance easier. And when proposing the new alternatives, be sure to consider equipment, such as extended-life lamps, programmed-start ballasts, parallel-circuit operation, fixtures with easily accessible features and minimal components that can easily be removed for servicing, etc. Also be sure to propose environmentally responsible disposal of replaced equipment.
Based on these benefits, proper maintenance can provide an edge in lighting upgrade projects.
DILOUIE, a lighting industry journalist, analyst and marketing consultant, is principal of ZING Communications. He can be reached at www.zinginc.com.