Can you run small amounts of romex (10-2 awg) inside schedule 40 with out worries of overheating. Which I.D would you use 1/2" or 3/4"if expectable? This is all above ground.
NM cannot be used outside, even in conduit.
Greetings Michael -
Jim is 100% correct.
I figured I would also (since I am visiting) I would answer the remainder of your question. If you are installing the Type NM-B Cable (proper name) inside of a small portion of open ended raceway in order to protect against damage to the cable assembly then it would be permitted. However, this does not translate into using Type NM-B in a complete run of a raceway without a solution to the securing requirements the boxes or enclosures.
Now, I will assume you are doing a good amount of Type NM-B inside a raceway in order to protect it which in that case I would send you to Chapter 9, Table 1 and subsequently note (9) for the explanation of the side of the Type NM-B to use, which is the major diameter (flat side) for your fill requirements which would be 53%.
Most all manufactures (at least we do) provide the diameter information on our product specification sheets as well. However, since you used the term “Romex” we will assume you are not talking about our product so I am not sure if they provide their diameter information without you actually having to measure it.
Now as Jim stated , Type NM-B is a DRY location only product so when you said “above ground” this could technically be accurate inside of a dwelling as well…but I agree with Jim as it sounds like it was an outdoor kinda question…to which is clearly a NO-GO for Type NM-B…but you always have Type UF-B as an option if that is the case.
Hope you found this helpful…and Good Luck !