Bill & Sparky,
Boy, I read the question differently. When I first read it, I assumed Courtland was referring to quality control testing by a manufacture or if listed components are used in a listed assembly do the components need to be tested and/or listed again for the assembly.
I work for a company that manufactures small quantities of UL listed products, and assembles ETL control panels. We test and/or inspect each individual item but I do not know what the listing requires. Now I am curious and need to ask one of the engineers at work what is required.
By the way, I am not an electrician; I work mostly on the mechanical ends of things. I work with pumps and electrically actuated and controlled devices. Thus, I have a keen interest in electrical and enjoy learning more about it from this site.
Phil H
