How to Identify the Types of Household Electrical Wires

How to Identify the Types of Household Electrical Wires

Identifying the types of electrical wires in your home is an important skill for any homeowner to have. Knowing the specifics of your home's wiring allows you to complete electrical projects safely and choose compatible devices and components. In this article, I will provide an in-depth guide on how to identify common types of household electrical wires.

Non-Metallic Sheathed Cable (NM, NMC)

Non-metallic sheathed cable, commonly abbreviated NM or NMC, is the most common type of electrical wire found in modern homes. Here are some ways to identify it:

Metallic Sheathed Cable (MC, AC)

Metallic sheathed cables, or MC and AC, are armored cables protected by an outer metal covering and waterproof coating. They are found in old homes built before the 1960s:

Knob and Tube Wiring

Knob and tube wiring consists of individual rubber insulated wires run through ceramic knobs, tubes, and flexible conduit:

Bundled Service Entrance Cables

The service entrance cables that provide power to your home have multiple insulated wires bundled together in a thick protective sheathing:

Identifying Wire Size and Type

In addition to the cable jacket, you can examine the individual wire insulation to determine size and type:

When in Doubt, Call an Electrician

Identifying wires is a useful DIY skill. But if you cannot determine the type of wiring in your home, the safe option is to call a licensed electrician to inspect. Professionals have the tools, testing equipment and experience to safely and correctly identify wiring. They can ensure your home's electrical system is up to code.

In summary, the type of cable, jacket markings, sheathing materials, insulation colors, wire count and size all provide clues to identifying common residential electrical wires. Match your home's wires to these descriptions to decipher which is which. Being able to identify electrical systems allows you to better understand your home and make informed upgrades.