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Three Types of Electrical Wire: THHN, UFB, and Romex Wire Revealed

There are many types of electrical wire available for consumers, however, it’s easy to get confused by the different types. The most common types of electrical wire are THHN, Romex, and UFB wire. However, in order to understand which electrical wire will do the best job for a specific project, it’s best to know the capabilities of each kind of wire.

  • THHN Wire

THHN wire is covered with a PVC jacket and nylon coating. This wire is a bare one conductor copper wire and is often used indoors or in conduit. The most popular sizes for THHN wire are 12 and 4/0, though other sizes are available for nonstandard projects. The PVC jacket is one of the cheapest forms of insulation for this type of wire and the nylon coating provides waterproofing and slight lubrication for placing in a conduit. Because of the ‘bare essential’ nature of this wire however, it isn’t recommended for outside use.

  • Romex Wire

Romex wire is made out of two or three THHN wires combined with a grounding bare copper wire. Like the THHN wires, Romex wire can’t be used outside because of its minimal PVC jacket protection. However, these wires come in larger sizes than the thinner THHN wires; 14/2 and 6/3 are used widely as electrical wire, despite the fact that it can’t be used in conduit at all. The primary use for this type of wire is to run more than one conductor at a time through a separate grounding wire.

  • UFB Wire

UFB wire is one of the most popular and versatile brands of wire available, though it’s also the most expensive. It can be used in conduit, outdoors, underground, you name it. Because it deals with tougher terrains than THHN or Romex, UFB wire comes in larger sizes, most commonly 6/3 and 8/3 and is often called ‘underground cable’.

The more jobs that an electrical wire does, the more expensive it is. It’s important to know what the different electrical wires do before committing. Frequently, that added expense can save a lot of costly replacements and time-consuming repairs.