You’ve got equipment that needs a field evaluation, and somewhere inside the machine looms an unlisted component. It may not necessarily be hiding in the shadows twirling a mustache, but close enough. It hasn’t been formally certified by a Nationally Recognized Testing Laboratory (NRTL) such as UL or CSA, and now you’re wondering whether you’ve accidentally built a monument to paperwork. 

https://productsafetyinc.com/how-are-unlisted-components-accepted-during-field-evaluations/