Must wirenut connection be wrapped??

I had a little argument with a friend of mine that I need a clarification per code. After wirenuts are used for connection, must it be wrapped with a black tape?? After I verify the tight connection, I usually do not wrap it. My buddy tells me I'm doing an illegal thing.

Am I right or is he right??

 

No,, you need not tape it,,, I dont like to twist the wires before installing nuts,, let the wire nut do the twisting.

 

Simple argument solvable.
Ask him "Show Me the code ref."
Using a standard wingnut. Then the answer is no.

 

No, ordinairly, but if one were wiring a motor and there might be some vibration there, then it would be a good idea to go ahead and wrap the wirenuts real good. All electrical components should be installed per the manufacturers instructions, and you most likley won't find a wirenut manufacturer specifying tape with their product. Some however in the past have recommended that you don't need to pretwist the conductors when using their product. Just insert the wires and let the metal portion of the wirenut cut into and twist the wires, ans check to see that it worked. It takes a while to get real comfortable doing it without pretwisting.