UL Question Corner

UL Question Corner: Low Voltage LED Luminaire Drivers

Q. I have encountered Listed low voltage LED luminaires shipped without a driver. Do I have to use a power supply/driver that is specifically Listed as an LED driver or low voltage lighting power supply? 2017 NEC 411.4(B)(2) just requires a Listed power supply. Listed for what?

A. Certified (Listed) low voltage luminaires are required to be shipped with installation instructions. If those installation instructions identify a specific driver or power supply for use with the luminaire, or define a specific power limitation for the power supply, e.g., Class 2, then NEC 110.3(B) requires that the specific power supply or power limited type of power supply be used. If the Certified (Listed) low voltage luminaire installation instructions are silent on the issue or only define luminaire input ratings, then the luminaire is compliant with the UL Certification (Listing) and with 2017 NEC 411.4(B)(2) provided that the power supply or driver:

  • Is Certified (Listed)
  • Complies with NEC 411.3 and
  • Is appropriate for the input rating of the luminaire

Unless the luminaire installation instructions specify otherwise, the Certified (Listed) power supply or driver required by NEC 411.4(B)(2) is not required to be Certified (Listed) as a low voltage lighting power supply or LED driver. Instead, it can be Certified (Listed) as a Class 2 or information technology equipment (ITE), general purpose or specialty power supply, or other type of Certified (Listed) power supply as long as the output characteristics of the power supply are appropriately sized for the luminaire input ratings.

For several Code cycles prior to the 2017 NEC, Section 411.4(B)(2) required Listed low voltage luminaire power supplies. In the 2017 NEC, Section 411.4(B)(2) simply requires a Listed power supply and not a low voltage luminaire power supply.

Low voltage luminaires and power units can be Certified (Listed) under the UL product category Low-voltage Lighting Systems, Power Units, Luminaires and Fittings (IFDR) and are investigated for compliance with UL 2108, the Standard for Safety for Low Voltage Lighting Systems. The UL guide information for IFDR has been revised to provide more clarity for these installations. The UL guide information and Certifications (Listings) for IFDR can be located on UL Product Spec at www.ul.com/productspec; enter IFDR at the category code search.

Q. Some low voltage lighting luminaire installations use a Listed ITE (information technology equipment) power supply that is marked “LPS.” Are “LPS” power supplies considered the equivalent to Class 2 power supplies? What does “LPS” stand for?

A. Yes. NEC 725.121(A) permits Listed (Certified) information technology equipment limited-power circuit power sources for Class 2 and 3 circuits. “LPS” is an acronym for Limited Power Source from UL 60950-1, Standard for Safety of Information Technology Equipment – Safety – Part 1: General Requirements.

These power supplies are Certified (Listed) under the UL product category Power Supplies, Information Technology Equipment Including Electrical Business Equipment (QQGQ). The UL guide information and Certifications (Listings) for this category can be located on UL Product Spec at www.ul.com/productspec; enter QQGQ at the category code search.

Figure 1. LED Driver for 12-volt LED Lighting
Figure 1. LED Driver for 12-volt LED Lighting
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