subject: Are The Inner Conductors Of Romex Hook Up Wire? [print this page] Technically yes, but it depends on the type of hook up wire youre talking about. Hook up wire is basically defined as a single conductor wire that hooks up power to something. Standard types of hook up wire are THHN, UL1007, UL1015 and Type E PTFE wire.
The inner conductors of Romex electrical wire are THHN dual rated with THWN. THHN stands for Thermoplastic High Heat Nylon and the additional W in THWN stands for Water resistant. This type of electrical wire is included in most of the cables in the industry such as Romex (NMB cable), MC cable, UFB cable, Service Entrance cable and tray cable.
Each type of electrical cable has a different jacket that approves them to be used in different types of environments. Each new approval will make it slightly more expensive than the previous type because it will have to be tested and approved for the listed characteristics.
Using THHN THWN wire on its own will grant you the ability to use it indoors, outdoors and in conduit. Its rated for 600 volts, 90C and resists oils, gasses, chemicals and moisture without a problem. The reason that Romex is an indoor cable, even though its conductors are available to be used outdoors, is due to the bare copper ground wire. The thin PVC jacket cannot protect the bare ground wire from outdoor applications.
UFB cable is another type of electrical cable on the market that can be buried directly underground. The added protection of the UFB jacket compared to the Romex jacket approves the cable for underground use without conduit. This is another very common, but slightly more expensive, cable in the electrical industry.
Even though THHN is considered a type of hook up wire, in general, its the only one used in Romex and should not be confused with UL1007, UL1015 or Type E PTFE wire. UL1007 and UL1015 are types of appliance wire and commonly used in electronics as a wire harness or assembly. Type E PTFE wire is a high temperature wire used in applications up to 200C. The highest temperature rating between the other three types of hook up wire discussed here is 105C.
Make sure you speak to your wire and cable distributor about the approvals of the lead wire you need before trying to hook up your application. There are temperature, voltage and environmental conditions to consider that you may or may not have realized.
