Is an LED right for your next retrofit project?

Building owners are asking lighting designers and electrical engineers to help them save on energy costs, and replacing fluorescent, HID, or other lights with LEDs is in high demand.

Tom Divine, PE, Smith Seckman Reid Inc., Houston

This article is peer-reviewed.Learning objectives:

As LED illumination technology improves in efficiency, reliability, and quality, building owners become interested in cost-effective ways to apply LED lighting in their facilities. In many cases, retrofitting existing fluorescent or incandescent luminaires will be an attractive alternative to wholesale fixture replacement. This article explores the effects of some of the applicable codes on LED retrofit projects.

In this case, an "LED retrofit" is the replacement of a luminaire's light source with an LED source while leaving some part of the fixture in service. A retrofit project also may include replacing other components, such as ballasts, reflectors, lamp holders, or lenses.

LED retrofit options

Many of the code issues that arise in LED retrofit projects are the same code issues involved in lighting-replacement projects, in which luminaires are removed and replaced in their entirety, while others have unique aspects related to retrofit projects, or to LEDs. Some of those code provisions are:

Figure 1: This graphical comparison of photometric distribution patterns shows two luminaires, one fluorescent and the other LED. This chart applies only to two specific fixtures and does not describe a general relationship between LED and fluorescent fix

LED retrofit kits can come in a variety of configurations. For fixtures using tubular lamps, these are the most popular options; government entities may have different requirements:

For downlights, retrofit kits normally provide for replacement of lamp holders with a self-contained unit containing an LED emitter and heatsink and a separate LED driver that replaces the ballast. A number of kits are available to retrofit screw-base lamps with one-piece units consisting of a trim ring, lens, emitter, and internal driver.

For exterior luminaires, particularly parking lot installations, the typical practice is to replace luminaires entirely while retaining the poles.

Energy codes

Retrofit of more than 10% of the lighting in a space must meet the lighting power density and lighting-control requirements of the energy codes. IECC requirements are invoked when more than 10% of the fixtures are modified, while ASHRAE 90.1 provisions become effective when more than 10% of the lighting load in the space is affected. Both codes require that the total lighting power does not increase for a project to enjoy the exception.

Figure 2: An LED retrofit fixture replaces a high-intensity discharge fixture in a parking garage, shown under daylight conditions. Courtesy: Smith Seckman Reid Inc.

Lighting power density

Retrofits involving simple lamp replacement, without other modifications, are likely to be viewed by AHJs as maintenance activities rather than alterations, thus they will not trigger requirements of the energy codes. IECC specifically describes projects that replace only lamps, ballasts, or both as repairs. ASHRAE 90.1 specifically establishes that projects replacing both lamps and ballasts must meet its provisions, but does not address lamp replacement alone.

For projects involving only lamp replacements, this exemption will avoid any necessity for compliance with the energy codes while still providing the owner with energy and maintenance reductions associated with LED lighting. However, for projects involving other types of retrofits in addition to lamp replacement, other provisions of the codes will exclude power reductions due to straightforward lamp replacements from the calculated lighting power density of the overall project.

For nearly all lighting retrofit projects, the lighting power densities allowed by the current editions of the energy codes are much lower than any that were in effect at the time the original lighting was installed. To comply, the retrofit fixtures must generally use considerably less power than the original fixtures. Engineers designing retrofit projects under these codes must verify that the specified retrofit kits can provide adequate illumination. The power density allowances of the energy codes will, to some extent, drive the selection of retrofit kits toward more efficient yet costlier options.

ASHRAE 90.1 9.1.4 requires that lighting power densities be calculated using the highest wattage of each fixture, as stated on its manufacturer's label or as determined from the ballast manufacturer's product literature. This provision may make compliance difficult, if not entirely out of reach. Because fixtures remain unmodified, their original labeling remains in force. For older, less efficient fixtures, actual power reductions as a result of lamp replacement won't impact the calculated value of the lighting power density.

More invasive retrofits involving removal or replacement of existing ballasts and other fixture components do not enjoy any repair exemption in the energy codes; when the threshold is reached, the requirements of the codes become enforceable.



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