I did not intend to overemphasize the importance of the degree to which something is secured into place. That is not a key issue, in my view of the limits of the NEC?s applicability.
The ?scope? paragraph of Article 100 essentially tells us that if the NEC does not have a specific definition of a term that it uses, then we must rely on our common understanding of that term. But the English language often offers many, many meanings for the same word. If you go to one dictionary, and find one definition that suits your interpretation of the code, you don?t get to say that THAT is the definition that the code makers intended this word to mean.
I saw the same terms in the definition of ?install,? when I looked in the dictionary on my desk. I still submit (and yes, this is only my own opinion) that the NEC?s use of ?installation? has a higher and more technically oriented meaning. Nothing requires a homeowner to buy a copy of the NEC, nor to conform to anything written within it. The NEC is not an ?operator?s manual.? If the HO buys a window AC unit, and secures it in place using two screws, and then plugs it into a nearby receptacle, then (1) The HO is ?installing? the unit, in the context of common English usage, and in the context of the definition in your dictionary and in mine, and (2) The HO is not ?installing? the unit, in the context of NEC article 90.2(A). No electrical permit is needed, nor should one be. The HO does not need, and should not need, the advice or assistance of an electrician, in order to plug in the unit.
If the unit requires a 220 volt outlet, and if there is none nearby, then it is an electrical installation task to put one there. In that case, the premises wiring system is being modified, and a new outlet is created. It is within the scope of the NEC, and it is a task best left to a professional electrician. But the act of plugging the A/C unit cord into that new outlet is not an electrical installation task. It does not modify the premises wiring system. It is not within the scope of the NEC, and the HO is not going to pay an electrician to do that task.