One of the most commonly encountered voltage ratings in residential and commercial wiring is 600 volt wire. But what is it used for and what are some of the most common types? This short post will explore that very question. 

What Is 600 Volt Wire and What Is It Used for? 

To keep things as brief as possible, 600 volt wire is wire that is rated to safely carry current at a potential of up to 600 volts. Common residential line service in the United States is either 120 volts or 240 volts, split phase. This gives 600 volt wire a fair buffer to protect it against overheating and other issues associated with exceeding the voltage rating. 

It also makes 600 volt wire among the most commonly encountered types of building wire in the United States, used for a wide range of applications. There are grades of wire at this rating that are used for lighting, powering appliances, and general purpose power distribution. In addition to their residential and commercial applications, they can also be used for some light industrial applications. 

Common conductor materials in 600 volt wire include copper and aluminum, with copper likely being the most commonly used because of its higher conductivity. However, because of its low cost, low weight, high conductivity to weight ratio, and some other factors, quadruplex and triplex wire used for power service entry are commonly made from aluminum, especially for aerial installations.

While 600 volt cable and wire have a wide range of potential applications and use cases, it is important to remember that they are not suitable for every installation, and that only wire or cable specifically designed for a certain type of installation or application should be used, based on the standards it meets. 

That being said, it remains the case that 600 volt wire enjoys a wide range of applications in residential, commercial and some industrial applications. So what are some of the common types you’re likely to encounter?

Common Types

There are many different common types of 600V wire and cable. Some of the more common are as follows. 

• THHW wire. This type of 600 volt wire is so named because the THHW stands for “thermoplastic, high-heat, wet”, indicating that it is protected by a thermoplastic sheath, and that the insulation is also resistant to both high heat conditions and wet environments. This can potentially make it useful in installations wherein it will be subjected to high heat or moisture. 

• THHN wire. In this case, the THHN stands for “thermoplastic, high-heat, nylon”. The main difference here is that this cable, while it is resistant to high-heat conditions, is not necessarily suitable for installation in environments in which it will be subjected to exposure to moisture. 

• NMB cable. The NM in NM and NMB cable stands for non-metallic, indicating that the sheath used to protect the cable is non-metallic. The “B” signifies that the insulation is resistant to relatively high temperatures of up to 90℃. One similar type of NM cable is NMC cable, which is more corrosion and moisture resistant than NM and NMB cable. NMC cable is also resistant to fungus. The insulation used protects the conductors without paper fillers, which effectively prevents not only moisture from intruding under the jacket, but which also prevents it from wicking. 

• Romex cable. Romex is simply a brand name for a specific type of NM cable that is commonly used to wire residential settings and in some light commercial applications. The brand has become so ubiquitous that sometimes NM cable is simply referred to as “Romex” cable, in the same way that most bandages are referred to as “band-aids” despite the fact that that is a brand and not specifically a type of product.

• VNTC tray cable. The VNTC is VNTC tray cable stands for “vinyl nylon tray cable” making the “tray cable” designator somewhat redundant. It is commonly used in industrial power distribution and control, as well as in lighting. An important aspect of VNTC cable is that it is rated as tray cable, which means it can be used in cable tray rather than in conduit, saving time and effort with installation and improving inspection down the line. 

• MC cable. MC, or metal-clad cable, is a special type of electrical cable that is protected by a flexible metal outer sheath. Metal clad, also sometimes referred to as armored cable, is commonly used in harsh industrial environments in which an outer metal sheath is needed to protect the wire and cable underneath. It is commonly used in mining, agriculture, and other similar demanding industries. 

Still Have Questions About 600 Volt Wire?

While we covered some of the more common types of 600 volt wire here, there are many others. If you still have questions about them or other types of electrical wire and cable, get in touch with us and we will be more than happy to assist.