WesBell Electronics
Wire and Cable Blog

NM-B Electrical Wire Information

NMB Electrical WireNM-B electrical wire is a very popular type of cable used throughout homes and buildings to bring power from the electrical box to the lights, outlets and appliances. The 14, 12 and 10 AWG circuit sizes are the most common household electrical cables because of the amount of AMPS they offer. Different manufacturers engineer different types of NM-B cable but all types must still meet a certain standard noted in the NEC or National Electric Code.

NM-B Circuit Sizes

NM-B electrical wire circuit sizes are the smallest 3 sizes which are 14, 12 and 10 AWG. The 14 AWG NM-B cables have a white outer jacket, the 12 AWG cables have a yellow jacket and the 10 AWG cables have an orange jacket to set them apart. These three cables run from the electrical box in your home, through the walls to your lights, outlets and appliance outlets. All you will see is an outlet or a light assembly instead of any wiring. Once you pull off the outlet casing you will see the wiring behind it.

Southwire Brand Romex® NM-B Cable

Romex® is a brand name of NM-B cable that Southwire manufactures. It’s similar to buying the brand name of Kleenex® instead of another brand of tissues. It needs to be manufactured to the same specifications per the NEC code but it can be enhanced. Therefore, buying another brand should suffice but buying a premium brand can sometimes lengthen the life of your electrical cable.

Larger Sizes of NM-B Electrical Wire

Larger sizes of NM-B cable refer to 8 AWG through 2 AWG with two or three possible conductors. The bare copper ground wire is additional and not noted when you see: NM-B 6/3. A 6/3 electrical wire will have 3 insulated conductors that are color coded and an additional ground wire without insulation. These cables are more often used to hook up an indoor hot tub, a large appliance or indoor shop equipment. They aren’t flexible at all and cannot be used outdoors either. Therefore, the entire connection must remain indoors if you plan on using NM-B cable or Romex® cable.

Knowledge is power in nearly every industry. Having the knowledge of a subject will allow you to buy and sell in an educated fashion. For instance, understanding that NM-B cables are priced based on the value of copper as a commodity, will allow a savvy buyer to purchase their copper cables at the correct time rather than just replacing a cable when the time comes up.

Written by: Chris Bell

Copper MC Cable Information

MC CableMC stands for Metal Clad which is derived from the aluminum armor that wraps around the conductors. Copper strands are used to conduct electricity, THHN insulation is used to protect the copper and aluminum armor is used as a jacket instead of duct for indoor applications. Copper MC cables also have industry approvals that allow it to pass inspection per the NEC code.

Copper Strands

Electrical cables are those used in homes and buildings either bringing power to the building or supplying smaller amounts of power throughout the building. Electrical cables are typically manufactured with stiff copper strands because it helps during the installation process. Pushing flexible cables through conduit and duct is difficult because it will bunch and get stuck. Stiff MC cable can be used indoors without conduit, outdoors and underground when in conduit or raceway. The only environmental application not safe for MC cables is directly underground because they don’t have enough protection.

In order to install a copper MC cable underground you will need to get the additional PVC jacket. The construction is exactly the same with an additional PVC jacket to create a water tight jacket and a cable available for direct burial applications.

THHN THWN Insulation

The term “insulation” is used to describe what covers the copper strands and the term “jacket” is used to describe the outer wrapping that covers all of the wires inside the cable. The MC cable conductors are covered with THHN THWN approved insulation. THHN stands for Thermoplastic High Heat Nylon which describes the materials used and protection it’s exerting. So, depending on the amount of conductors your cable has, 2, 3 or 4 THHN wires are bundled together and wrapped with aluminum interlocked armor.

Aluminum Interlocked Armor

The metal clad jacket, named aluminum interlocked armor, is very different compared to standard types of electrical cable jackets. It was designed to be used indoors for applications that require a cable and conduit together. MC cable is approved as a “cable and conduit” in one for indoor applications. It will pass inspection with approved THHN THWN wires and an approved metal clad jacket. MC cables can also be used outdoors and in conduit underground when necessary.

Please speak to your wire and cable supplier before making an electrical cable purchase. They can help match the most cost effective cable for your installation based on the environment it will be placed in. Getting an approved cable at the right price is what most contractors, electricians and installers want when they’re in search for copper cables.

Written by: Chris Bell
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600 Volt Unshielded Electronic Cables

Unshielded Electronic CableUnshielded electronic cables are those with multiple lead wires bundled together and wrapped with an overall jacket. A shielded electronic cable will also have a foil or braid shield between the lead wires and the jacket to block EMI (Electromagnetic Interference) when cables run side by side in an installation. The biggest difference between the various 600 volt unshielded cables lies in the type of protection the jacket offers which, in turn, describes where it can be installed without being damaged by its environment.

600 Volt PVC Electronic Cables

PVC (Polyvinyl Chloride) lead wires inside of a PVC insulated jacket is the most basic, low cost, electronic cable that you can purchase. Common applications for PVC cables are intercoms, public address systems, remote control circuits and related environmental applications. These types of electronic cables are most likely used indoors because the outdoor environmental conditions will be too tough for the basic PVC jacket.

600 Volt Fire Alarm Cable

Fire Alarm CableFire alarm cables typically come with a red jacket but there are various colors available depending on our inventory levels. They are commonly used to install fire alarms, security systems and other similar communication applications. These are manufactured with a PVC jacket or a Plenum jacket. The plenum jacket is used when the installation is in plenum or any type of above head duct for fire protection reasons.



600 Volt STJ PTFE Cables

Unfortunately, STJ cables only come in a shielded version because the amount of heat used to wrap the jacket around the conductors would melt the insulation of the lead wires during the process. Therefore, a shield is placed between the lead wires and the jacket to limit the amount of heat hitting the insulation of the wires. STJ stands for Shielded Tape Jacket and it’s an upgrade from PVC cables because it can handle applications with a temperature rating of up to 200ºC compared to 105ºC. STJ PTFE cables usually have a white tape wrapped jacket but also have the option of FEP extruded insulation which is not wrapped.

There are many different types of 600 volt unshielded electronic cables available in multi conductor, multi pair, higher voltage and higher temperature for each different type of installation. There are also jackets that are manufactured with more protection for severe weather and severe impact. Standard cables have been known to end up with cracked insulation and damaged conductors quicker than expected so it’s worth it to purchase a heavy duty cable when necessary for the application.

Written by: Chris Bell
ISO 9001 Certified