Cables and Their Uses
To understand cables, we’re going to start with a definition. The 2020 National Electrical Code (NEC), which is the current electrical code in North Dakota as of this writing, actually does not give a general definition of cable, but gives a definition for each cable type. But generally, the definition of a cable is “an assembly of one or more insulated conductors enclosed within an overall protective sheath”. This is different from a cord in the sense that cords are generally portable and made to be moved over and over, whereas a cable is meant to be installed once and stay put. Now let’s explore some different common types of cables.
1. NM Cable (Non-Metallic Sheathed Cable)
NM cable consists of two or more insulated conductors (wires) wrapped in a non-metallic sheath, usually made of PVC (polyvinyl chloride). The trade name for NM Cable is “Romex”, which is just a brand name like Kleenex. This is the cable that you see if you ever go to a new house being built. The different jacket colors signify different wire gauges and different number of ungrounded (hot) conductors. If you see, for example, “10/3” printed on the jacket, that means it is 10 AWG (American wire gauge) and there are 3 ungrounded conductors, a grounded/neutral conductor, and a gounding/bare conductor. White is 14/2, yellow is (usually) 12/2, orange is 10/2 or 10/3, purple is 12/3, blue is 14/3, and anything other than these are usually black.
2. UF Cable (Underground Feeder Cable)
UF cable is similar to NM cable but is designed for underground use or where it may be exposed to moisture or corrosion. It's used for outdoor applications like powering landscape lighting, underground wiring for outbuildings, and other applications where protection against moisture is necessary. UF cable is dark gray, and can be installed anywhere NM cable is installed, and I personally recommend it for any unfinished building even if it’s indoors. For example a pole barn.
3. AC Cable (Armored Cable)
AC cable has multiple insulated conductors wrapped in a flexible metal sheath (usually aluminum or steel). It is used in environments where mechanical protection and grounding are required, such as in commercial and industrial buildings.
4. MC Cable (Metal-Clad Cable)
MC cable also has multiple insulated conductors, but they are surrounded by a smooth or corrugated metallic sheath. It's used in commercial and industrial applications where additional protection against physical damage and moisture is needed.
5. SE Cable (Service Entrance Cable)
SE cable consists of insulated conductors with a bare neutral conductor and an overall PVC or rubber-jacketed covering. It's used primarily for outdoor overhead service entrances to residential or commercial buildings, where it connects the electrical service from the utility company to the building. It is also useful to supply a sub-panel in a building instead of running multiple smaller circuits. SE cable is not commonly seen in Minnesota or North Dakota, but it’s perfectly safe and legal to use.
6. USE Cable (Underground Service Entrance Cable)
USE cable is similar to SE cable but is specifically designed for underground installations, with a tougher sheathing material to withstand burial directly in the ground. Here is a nuance in calling USE a “cable” because instead of a jacket, it usually comes as three wires twisted together for its entire length. This is the wire you see going into your house at the weather head.
Each type of cable serves specific purposes based on its construction and intended use, ensuring safety, durability, and compliance with electrical codes and regulations. Beyond these there are many other types of cables. MI, DER, FC, FCC, IGS, and Type P cables are just a few of the other available options. If you need an electrician in Grand Forks to handle these details, call Prosperity Electric at (701) 335-6336 to get started today!
