According to the U.S. Department of Energy (DOE), in 2010, more than 75 percent of lighting systems installed in the commercial building sector were fluorescent, with the majority installed in recessed troffer luminaires. Since then, light-­emitting diode (LED) technology has advanced to offer comparable, energy-­efficient alternatives suitable for retrofit.


The primary options are linear (tubular) LED lamps, LED retrofit kits and dedicated LED luminaires.


Replacement linear LED lamps offer about a 10 percent efficacy (lumens per watt) improvement over fluorescent linear T8 lamps, but performance varies widely. While “drop-in” LED lamps that do not require electrical modification to the luminaire are available, the large majority of products require changing the luminaire’s electrical wiring, replacing the ballast with an external driver, or altering the lampholders (tombstones).


LED retrofit kits consist of lamps and electrical and optical components in a prepackaged unit, offering a repeatable solution. However, it is important to verify that the existing luminaire can accommodate the particular retrofit kit. The kit either replaces the ballast with an LED power supply or entails ballast removal with the LED module or lamp wired directly to the branch-circuit wiring. The LED light source may use original lampholders or be installed with new ones.


Dedicated LED luminaires are complete units that replace existing fluorescent luminaires. This option typically imposes a higher product cost but offers straightforward installation and the performance advantages of a purpose-built product. According to a 2013 DOE ­CALiPER report on recessed troffer lighting, LED luminaires are about 44 percent more efficacious than fluorescent troffers.


When installing any electrical product, safety is a key consideration. Any installed product should bear the mark of a nationally recognized testing laboratory (NRTL) such as UL, ETL and CSA.


New luminaires should already have required safety certifications, with the cost of certification absorbed in the purchase cost of the luminaire. The NRTL certifies and labels the luminaire as “listed.” The authority having jurisdiction (AHJ) determines if a listed product is acceptable.


When a fluorescent luminaire is modified in the field, questions arise about whether it continues to satisfy the safety requirements of its original listing. The AHJ determines whether luminaire servicing and retrofits require inspection. While replacing a fluorescent ballast like for like is typically regarded as servicing, replacing a T12 with a T8 ballast may not be so, because it changes the luminaire’s electrical characteristics. The same situation applies to LED replacement lamps and kits. Upon installation, the original safety certification and warranty may no longer be considered valid.


If an LED retrofit kit is installed, a product may be selected that is certified and marked as “classified” by an NTRL. In this situation, the modified luminaire is considered to meet the same level of safety as before the retrofit. The kit’s manufacturer provides a label to prominently affix to the luminaire, indicating that it has been modified and can only be used to operate the specific installed LED replacement lamp. The information on the label must match the installation instructions and other documentation.


If a linear LED replacement lamp is installed, there are two options. The first is to select a product that installs without modifications to the existing luminaire. These lamps operate on the existing ballast and lampholders, if verified as compatible. In this case, it may be NRTL-listed as a self-ballasted LED lamp.


The second option is a linear LED replacement lamp that requires electrical modifications to the luminaire. Most linear LED replacement lamp products are in this category. The LED driver may be integral to the lamp, requiring line voltage be supplied to the lampholders and with the lamp being single- or double-ended in terms of electrical connection. Or, the lamp may have an external driver, which is connected either to the existing lamp-holder or directly to the lamp, with the existing lampholder used for position and stability. In this case, on-site inspection and field-safety certification by an NRTL would be needed, imposing an additional cost. This solution may entail line voltage being delivered to the sockets, creating a hazard if a fluorescent lamp is reinstalled later. For this reason, the luminaire should be clearly labeled that it cannot be used with the originally intended lamps.


Verify that all LED products are being installed in appropriate applications in accordance with product markings and manufacturer instructions. The Qualified Products List, published by the DesignLights Consortium (www.designlights.org), identifies suitable performance criteria for linear LED replacement lamps and compliant products.


This article is meant to provide general educational information. For specific requirements related to your project, consult the manufacturer, the AHJ, or check UL 8750 (LED Equipment for Use in Lighting Products), UL 1993 (Self-Ballasted Lamps and Lamp Adapters) and UL 1598C (LED Retrofit Luminaire Conversion Kits). UL’s guide, “Luminaire Ballast Retrofits and Conversions,” is available at www.ul.com.