Your intuition that NM and THHN should be priced similarly per wire-foot (length of cable * number of conductors in cable) is indeed correct -- the copper content is the main driver of the price of the finished product.

THHN cable contains a single thermoplastic high heat-resistant nylon wire, while the former conductors of NM B are basically THHN wires. This is what creates the most confusion between the types of cables. No, it’s time that I take you through a detailed tour of both of these wires.

Oct 18, 2010 · Guys, I've been getting different answers from local electricians on the ampacity of 8 guage wire. Some say it will carry 50 amps, others (including the NEC charts) say 40 amp. Apparently, there's a difference between whether it is NM Romex or THHN.

Oct 28, 2020 · The wires inside romex aren't exactly the same as THHN -- in particular, THHN has a tough outer clear plastic coating around the main softer insulation, which makes it easier to pull through conduit without damage. A few electrical supply houses "stick it" to random walk-in consumers because they think they'll be "high maintenance".

Dec 6, 2024 · THHN wire stands for Thermoplastic High Heat-resistant Nylon-coated wire. It is a versatile electrical wire that is widely used for indoor wiring in both residential and commercial settings.

Oct 26, 2015 · The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The allowable ampacity shall not exceed that of a 60°C (140°F) rated conductor.

Nov 12, 2021 · In residential and commercial wiring, Romex (NM-B) and THHN are two of the most common types of cables used. The confusion is that the NM-B wire is not that far from THHN in terms of construction. Whereas THHN is a cable with a single thermoplastic high heat-resistant nylon wire, NM-B wire is a sheathed cable with multiple conductors.

Mar 2, 2021 · THHN and Romex® are two of the most commonly used electrical wire types. However, there are notable differences between the two. To understand which wire is best for your project, you must know the capabilities of each wire type.

Dec 29, 2024 · Yes you can install NM (Romex) cable inside of conduit, as long as it's in a dry location indoors. Once you get outside you will need to use THHN/THWN conductors. Even though its inside conduit, by code it's still considered damp location.

Understanding Ampacity: Ampacity refers to the maximum safe current a conductor can carry continuously under specific operating conditions without exceeding its designated temperature limit. Current is measured in amperes (amps).