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FAQ - Double-Ended LLT vs. Single-Ended LLT

Question: What is the difference between the double-ended LED LLT and single-ended LED LLT?

Answer: The main difference lies in the rewiring when retrofitting for existing fluorescent fixtures. Figure 1 below shows the standard wiring diagram of a fluorescent fixture. When installing a double-ended LED LLT with an internal power driver, rewiring is required to bypass the ballast, as indicated with the black line in Figure 2. In comparison, when installing a single-ended LED LLT with an internal power driver, the retrofitting work involves both bypassing the ballast and rewiring the sockets (or tombstones), as shown in Figure 3. As such, when both options are possible, retrofitting a single-ended LED LLT requires more work than a double-ended LLT. In other situations, however, when the two sockets of the tombstone of the existing fluorescent fixture are shorted, as is often the case, it is not possible to retrofit a single-ended LLT.

Figure 1.

Figure 2.

Figure 3.

Question: If the double-ended LLT is easier to install and use, why doesn't everybody use it?

Answer: The short answer is safety requirements. The LED lighting industry initially introduced the double-ended LLT for easy retrofitting into existing fluorescent fixtures. However, none of the early double-ended LLTs met UL safety standards 1598 and 1598B. In response, single-ended LLTs were created to satisfy UL standards, as only one end of the LLT conducts electricity and there is therefore no risk of electrical shock when touching both ends of the LLT. It is only recently that the UL-classified double-ended LED LLT emerged on the market.

Question: Is it true that some companies are selling double-ended LLTs under the UL certificates of their single-ended LLTs?

Answer: Unfortunately, this is true. Certain companies that have been unsuccessful in designing a double-ended LLT that meets UL safety standards have taken to misleading customers by using the UL certificates of their single-ended LLTs. It is highly recommended that when purchasing double-ended LED LLTs the buyer ask the seller for the UL certificate of their double-ended LLT.

Question: Does aleddra offer UL-classified double-ended LED LLTs?

Answer: Yes, aleddra has received UL-classified certification (#E325073) for its T8 double-ended LLTs at 110-volt and 277-volt for direct fluorescent linear lamp replacement in existing fixtures. aleddra LED LLTs feature a double-safety switch design, which prevents electrical shock during installation, making it a safe and effective alternative for lighting contractors, maintenance professionals and facilities looking to reduce energy consumption for their projects. aleddra now offers 2-ft, 4-ft, and 5-ft T-8 LED LLTs engineered with the double-safety switch. More ...

Question: Is aleddra's LLT with the double-safety switch design under patent protection?

Answer: Yes, aleddra's LLT with the double-safety switch design has been granted protection under U.S. patent #US 20110149563A1.

Question: Is aleddra open to new distributors/resellers/dealers?

Answer: Yes, aleddra is always looking to expand its market through a strong business partner network as we strongly believe that local markets are best served through local partners. aleddra's business partner network is growing quickly. If you are interested in becoming a member of our partner network, please email us at



LightFair 2017
Philadelphia, PA
May 9-11, 2017


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