Beta field trials with 120VAC non listed power supplies

Any provision in NFPA 70 to allow for use of non-listed/recognized/ labelled 24dc power supply? presumably, it will be class 2 type.
We have a computer based product that will be powered by a 120vac-24dc power supply that is currently being listed, however, our project cannot wait the months it will take in order to begin deploying in the field.
Thanks, Jason
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Class 2 power supplies shall be listed and are readily available on the market. However, listed computers are given slack see (4) below.
725.41 Power Sources for Class 2 and Class 3 Circuits. (A) Power Source. The power source for a Class 2 or a Class 3 circuit shall be as specified in 725.41(A)(1), (A)(2), (A)(3), (A)(4), or (A)(5):
(A)(4) Listed information technology (computer) equipment limited power circuits.
FPN: One way to determine applicable requirements for listing of information technology (computer) equipment is to refer to UL 1950-1995, Standard for Safety of Information Technology Equipment, Including Electrical Business Equipment. Typically such circuits are used to interconnect information technology equipment for the purpose of exchanging information (data).
Here is the whole section: III. Class 2 and Class 3 Circuits 725.41 Power Sources for Class 2 and Class 3 Circuits. (A) Power Source. The power source for a Class 2 or a Class 3 circuit shall be as specified in 725.41(A)(1), (A)(2), (A)(3), (A)(4), or (A)(5): FPN No. 1: Figure 725.41 illustrates the relationships between Class 2 or Class 3 power sources, their supply, and the Class 2 or Class 3 circuits. FPN No. 2: Table 11(A) and Table 11(B) in Chapter 9 provide the requirements for listed Class 2 and Class 3 power sources. (1) A listed Class 2 or Class 3 transformer (2) A listed Class 2 or Class 3 power supply (3) Other listed equipment marked to identify the Class 2 or Class 3 power source Exception No. 1: Thermocouples shall not require listing as a Class 2 power source. Exception No. 2: Limited power circuits of listed equipment where these circuits have energy levels rated at or below the limits established in Chapter 9, Table 11(A) and Table 11(B). FPN: Examples of other listed equipment are as follows: (1) A circuit card listed for use as a Class 2 or Class 3 power source where used as part of a listed assembly (2) A current-limiting impedance, listed for the purpose, or part of a listed product, used in conjunction with a non-power-limited transformer or a stored energy source, for example, storage battery, to limit the output current (3) A thermocouple (4) Limited voltage/current or limited impedance secondary communications circuits of listed industrial control equipment (4) Listed information technology (computer) equipment limited power circuits. FPN: One way to determine applicable requirements for listing of information technology (computer) equipment is to refer to UL 1950-1995, Standard for Safety of Information Technology Equipment, Including Electrical Business Equipment. Typically such circuits are used to interconnect information technology equipment for the purpose of exchanging information (data). (5) A dry cell battery shall be considered an inherently limited Class 2 power source, provided the voltage is 30 volts or less and the capacity is equal to or less than that available from series connected No. 6 carbon zinc cells. (B) Interconnection of Power Sources. Class 2 or Class 3 power sources shall not have the output connections paralleled or otherwise interconnected unless listed for such interconnection.
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taistoi wrote:

What type of product is it... household? Commercial? Industrial? Is this power supply built in to the product? Is it a small "wall wart" type that plugs in? Permanently connected rack-mount? Do you intend to list the entire product with UL?
Nobody can quote relevant Code requirements, assuming there are any, without knowing a little more about the application.
--
Benjamin D Miller, PE
www.bmillerengineering.com
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