Tech Talk: DC Power Supply and Class 2 Labels

Q. The Inspector says my DC power supply needs a Class 2 label. What’s he talking about?

The Inspector is referring to the requirements of Class 2 circuits and wiring as defined in the National Electric Code (NEC). The definition of Class 2 circuits specifies the wiring system between the load side of a Class 2 power source and the connected equipment. The definition includes current and voltage limitations [NEC Table 11(A) and Table 11(B)] to limit the possibility of fire initiation and electric shock. Class 2 circuits offer reduced requirements for wire size, wire insulation, over-current protection, wiring methods and installation materials and can be advantageous in reducing cost and improving flexibility of an installation. Also, many local municipalities now require that the NEC Class 2 standard be maintained in public buildings, schools and hospitals.

To be approved by the local Authority Having Jurisdiction (AHJ), one requirement for a Class 2 circuit is that the power source for that circuit must meet the definition of a Class 2 power source as specified in the NEC. In accordance to NEC 2017, a Class 2 power source for DC powered circuits must be a listed Class 2 power supply [NEC Article 725.121(A)]. A listed Class 2 DC power supply is tested and certified by a third-party testing organizations like Underwriters Laboratories to meet Class 2 requirements and will have a label designating it as a listed Class 2 power source. Kele offers a selection of listed Class 2 DC power supplies. Look in the Power Supplies section of and some models of the PS5R Series that carry the Class 2 listing.


2 thoughts on “Tech Talk: DC Power Supply and Class 2 Labels

  1. I’m hoping that you might be able to help me. I came across a few very old new stock of NEC PD640G400B with power supply. The guys in Japan bought all 5 but, I have a power supply left. NowI have searched the Internet every department of NEC and nobody has any information on the 10 ounce for the display and the power supply isn’t classified with an input source it has blue black and red leads for the power do you have any information on what the input power might be on this board? I can send a picture if you need thank you so much and I hope to hear from you soon

    1. Good afternoon Todd,

      The display in question is a component to a larger system and would need a power supply. However I cannot find any information on the display to tell me what power source your need. (12AC, 12DC, 24AC, 24DC, 120AC, etc.) If it is left open (without an enclosure) then you will need a Class 2 power supply but I do not know which one you need to meet the power source requirements.

      This does not look like a typical component that KELE sells or has ever sold. It may have been a special request from a customer which explains the lack of supporting data in our system.

      Thank you for your question. If we can help you further, please contact our technical department at 877.826.9045.

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