590.4(G) Splices.
A box, conduit body, or other enclosure, with a cover installed, shall be required for all splices.
Exception No. 1: On construction sites, a box, conduit body, or other enclosure shall not be required for either of the following conditions:
(1) The circuit conductors being spliced are all from nonmetallic multiconductor cord or cable assemblies, provided that the equipment grounding continuity is maintained with or without the box.
(2) The circuit conductors being spliced are all from metal-sheathed cable assemblies terminated in listed fittings that mechanically secure the cable sheath to maintain effective electrical continuity.