I have installed 9 "QuiteWarm Radiant Heat Film for under subfloor" to heat the floor above a crawl space off the the basement. The crawl space has a concrete slab and is tempered. This subfloor system is a 120v. system, with a total load of 900 watts, 7.5 amps for the 9 panels. Each radiant heat film panel comes with a separate black and white 12 ga. wire. The instructions say to run all the wires (black and white)to a junction box, wire them in parallel and run a 12/2 Romex to the Thermostat. The Thermostat gets power from a separate 15 amp breaker circuit. The thermostat has a built in GFI. My question concerns the single 12 ga. wires from the film panels to the junction box. Can the single 12 gauge wires be run exposed in the crawl space(fastened per code along joist or 2x6) or do they need to be put in conduit or something else?. Thanks
Yes a crawl space can have your 12/2 attached directly to the floor joists if going along the joist if going perpendicular a rat run is needed for smaller than 2 ea #6 or 3 ea #8 wires see exhibit 334.1 in the code , nmb in this location has been code for decades. Rat run or 1/2” plywood minimum. Note bored holes need no protection.