- Is pretwisting conductors required when using wirenuts?
This question is not answered in the NEC, it is a product listing question. Products are required to be used in accordance with their listing by 110.3(B).
Most (if not all) wirenuts are listed for use as follows: Pretwisting the conductors is not necessary, but not prohibited - as long as the conductors are twisted once the wirenut is in place, then the manufacturer's instructions have been followed and the code is satisfied. If the connection is not twisted, then there is a 110.3(B) violation when using most (if not all) brands of wirenuts.
That said, most electricians will agree that a pretwisted connection is the most professional method, as it allows the installer to see without a doubt that the connection is tight before installing the wirenut.
But pre-twisters and post-twisters are all welcome here.