Under the 2020 NEC, I'm looking to add an extra fan to a freestanding gas fireplace beyond the built in blower. The extra fan is an ordinary wall fan with a 15A/120V plug.
The existing blower uses a 120℉ on and 90℉ off temperature switch connected by magnet to the fireplace.
The existing blower uses insulated disconnect terminals for all of its connections. There's no ground on the blower's switch, and there's no ground on the analogous switches that I've been able to source. Here's a quick schematic:
My wall fan's circuit seems easy enough to build if I naively analogize to the existing blower's circuit. I anticipate, however, that I'm entering a minefield and that my bumbling will land far away from code conformance.
My first instinct was to use the blower's current draw to trigger a relay feeding the fan. The "current switches" that I found required a minimum current draw of 0.25A (for tools triggering dust collection) which is my blower's exact rating. The dang blower is obnoxiously loud at full throttle, so I rejected these "current switches." If there exists a more sensitive switch (say 0.05A or 0.10A) that's reasonably priced, then coupling the fan and the blower becomes a viable option. Without anticipating a dust collection use case (and an inline blower use case), I probably wouldn't have found any such switches. I would love to learn of any other name besides "current switch" for these trinkets.
Assuming that I install a new double gang box with a 15A receptacle in one side for the wall fan, does there exist some combination of cable plus strain relief gland that I can legally use for diverting the receptacle's hot, where the cable would integrate the temperature switch into the circuit? Both of the cable wire ends (no ground) would not technically be exposed, but the insulation of the required female disconnect terminals make me uncomfortable. The uninsulated male disconnect terminals on the switch make me uncomfortable.
Assuming that the cable with technically unexposed wires is no good, can I terminate the cable at a metal gang box? The metal box would conduct the fireplace's heat to a switch that is wholly contained within the box. Could I get away with "fastening" this box to the fireplace by magnet? If not, then could mechanical fastening make it code conformant?
Any other ideas?