Can THHN cable be run without a sheath or conduit? We need to install a new residential sub-panel from a crawl space to a new full basement. The branch circuits currently going to the old sub-panel need to be junctioned and relocated to the new sub-panel. We would like to get a cable assembly made of 15 #12 THHN wires, and two #6THHN (for the neutral and ground), then attach the assembly to the overhead joists in the crawl space where they will run to and into the new panel in the basement. I think this meets the requirement of being physically protected since the crawl space is not accessable for storage. We have also, on occasion run a single #14 THHN for smoke detector interface wire. Do these applications meet code?