I am connecting a humidstat to furnace. I would normally use furnace/thermostat wire for this purpose except that I need 8 conductors and the largest furnace/thermostat wire seems to be 5 conductors. I would like to use another 18guage 8 conductor wire but not sure if there are any specifications I need to ensure it meets before I can use it inside furnace cabinet.
Standard 18 gauge wire is all you need, they do make it in 8 and 10 conductor, it just takes a little calling around to supply houses to find it. There's is nothing special about the wire specs for thermostat wire as it relates to your furnace so long as you use 18 gauge standed or solid wire. The only exception for thermostat wire is when you get into commercial buildings with an open plenum return air system, any wire used in the plenum cavity must be plenum-rated, which is almost always much more expensive.
bill this project seems to be taking you forever, may i ask why do you need 8 conductor?
they do make 8 and ten conductor stat wires but in a pinch you could run two 4 conductor wires side by side. just make sure you mark at both ends becayse you will have 2 of each color wire. mark them as red 1 and red 2, etc.
