Right, Greg ... but it's quite possible for a dairy to find itself in a conflict between different inspectors. If the USDA guy says "I want it welded, smooth, with no place for germs to collect," that's what will happen.
I said nothing about hard-wiring. Any appliance is, by definition, beyond the scope of the NEC. Open up nearly any appliance - UL listed included - and you'll easily find all manner of 'violations' in wire sizing, overcurrent protection, bend radius, and conduit fill. FWIW, you'll also see wires routed through all manner of raceways that are not recognized by the NEC.
Perhaps the simplest example is the ordinary table lamp. The cord certainly isn't #12 gauge, even though we plug it into a 20 amp circuit. That bored hole through the base isn't a recognized raceway. Yet, UL has no trouble listing it (to a non-NEC standard) because it's an appliance.
Further, as a general principle, there is no requirement that appliances be listed or approved by anyone. That many -especially consumer ones- are is the result of marketing, not regulation. Step away from the consumer marketplace, and listing marks, especially for complete assemblies, become pretty rare.
Or, as I like to point out .... Apollo 11 was NOT UL listed. Nor are the Abrams tank, the Boeing 747, the USS Enterprise, or even the family car. It just happens that we, as electricians, happen to work in the market that is most heavily penetrated by UL.
Now ... lest anyone think I'm being cavalier ... there have been times when I, or my employer, was forced to act contrary to the NEC's (or other codes') specific requirements. Such should not be done carelessly; in the instances that I participated in, there were specific reasons, and other documents (UL, NEMA standards, for instance) were referenced to identify important requirements. In short, we were able to reasonably state that the 'work around' would meet every requirement the listed product would, as well as some the listed product could not.
