411.4 Listing Required.

Although this power supply is marked Class 2, there is another problem. Can you identify the code violation?
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Although this power supply is marked Class 2, there is another problem. Can you identify the code violation?

Code Change Summary: Revisions make it clear that Class 2 power sources and lighting equipment connected to a Class 2 power source must be listed.

This code change was developed by a subgroup of the NEC® DC Task Force appointed by the Technical Correlating Committee.

For many tears, Article 411 has been the go-to place for requirements on items such as low voltage landscape lighting. Newer technologies such as LED lighting are becoming more and more common. Many new homes have low voltage, under-cabinet lighting installed in the kitchen. These low voltage lighting systems are generally supplied by a Class 2 power source.

Having a new listing requirement for low voltage lighting equipment and Class 2 power supplies in 411.4 provides an additional informational resource and places the responsibility of verifying safety of the product in the hands of the nationally recognized testing laboratories.

A common inspection issue with low voltage under-cabinet lighting is determining if the power source installed by the electrician is actually a Class 2 power supply. If it is, then some of the small and discrete wiring cables listed in 725.179 can be used for a clean looking installation with minimal exposed wiring.

In the product listing requirements found in the UL White book for Class 2 and 3 power supplies, it is noted that Class 2 and 3 power supplies will be marked “Class 2 or Class 3”. If this marking is not present, then the power supply is by default a Class 1 power supply or is not listed. If the power supply is Class 1, then only the bulky wiring methods mentioned in Chapter 3 can be used. A UL listed Class 2 power supply is required to bear the UL listing mark on the product.

References used for the above commentary:

UL White book product category XOKV, NEC® 411.5(A), 725.46, 725.130(A), 725.130(B), 725.179.

Below is a preview of the NEC®.  See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2011 Code Language:

411.3 Listing Required. Lighting systems operating at 30 volts or less shall comply with 411.3(A) or 411.3(B).

2014 Code Language:

411.4 Listing Required. Lighting systems operating at 30 volts or less shall comply with 411.4(A) or 411.4(B). Class 2 power sources and lighting equipment connected to Class 2 power sources shall be listed.

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411.4 Listing Required.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true for a lighting system operating at 24-volts?

A: The Class 2 power supply and the lighting equipment fed from it must be listed.
B: Only the Class 2 power supply must be listed.
C: Only the lighting equipment fed from the Class 2 power supply must be listed.
D: Listing is NOT required for the lighting system.
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