Do custom electrical control panels for equipment have to be UL listed/ have UL components?
This is a common question, all ready asked a few times. The answer is; 'it depends'.
Many panels are built without U/L listing. For their panels, ultimately, the AHJ has to either approve the use of this panel and its components, or disapprove of it. Building it with U/L components would greatly simplify this process.
It is unclear what you are asking. In the title (question) you say, "custom electrical panel" however in the first sentence you say, "custom electrical control panel." These are two distinctly different animals. Electrical panels fall under Article 408, while Industrial (electrical) control panels fall under Article 409.
408 - Speaking as an AHJ, if you make a panelboard that isn't listed, I would not approve the installation. There is just too much to consider.
409 - For an industrial control panel, if the industrial control panel is intended as service equipment, it shall be marked to identify it as being suitable for use as service equipment. I don't believe it is possible to get that marking without it being listed. For other types of industrial control panels I might approve the installation, depending upon what is being installed. If it is part of some complex system such as a dust collector system, for example, I would probably require the listing.
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