THHN is a heat resistant thermoplastic insulated conductor, usually a single conductor. Romex is a brand name for a nonmetallic sheathed cable, it has multiple conductors inside, the insulated ones are insulated with THHN insulation.
Romex is a manufacturer's wire cable trade name and not a wire size.
many wires are. such as 14-2 Romex. 12-2 Romex. Any THHN wire of any size. This list is very long. If you have a speific application then you need to check the NEC 2005 Table 310.13 Conductor Applications and Insulations.
UF cable(underground Feeder) Looks like romex, gray jacket. usually approved for direct burial. Check local electrical codes for burial depths, or if conduit is required. if conduit is required use THHN or THHN-2
n you run thhn wire in a cable tray
No, do not mix aluminum wire with copper wire.
No, you can feed it with a 2 wire Romex + ground. It depends on what is mounted on the ceiling. If it is just a light all you need is 2 wire + ground Romex. However if it is a fan/light and you want to control each one independant of the other you will need to use 3 wire Romex + ground. This is of course if you have 2 seperate switches. You would then connect the red wire to the blue light wire and the black wire to the black fan wire. If you use 2 wire Romex just connect the blue and black fan/light wire to the black wire in the ceiling box.
The exact year that Romex Wire came out is not listed on their website. However, they do say that they have been selling the wire for over 88 years. I have found the year 1926
ROMEX® is a federally registered trademarked brand of non-metallic sheathed electrical cable originally developed by the former Rome Wire Company in 1922. The ROMEX Brand is now owned and produced by Southwire Company.
NEC 310.16 #1 THHN Copper
The key is that you don't want to cause over-heating in wire. The answer is you can probably do what you want unless it involves high current and a small cross section in wire mold such that the Romex could generate too much heat. You could always strip out the wires inside the Romex and just run them in the wire mold.