What Type of Cable Is Used in Residential Wiring?

Introduction

When homeowners ask, “What type of cable is used in residential wiring?” they’re really asking how electricity safely travels from the panel to outlets, lights, and appliances throughout a house. Choosing the correct cable isn’t just a matter of convenience — it’s about safety, durability, and meeting electrical code requirements. For those looking to ensure high-speed network performance, Cat6 & Cat6a Cabling Installation Santa Clara has become a popular choice in modern homes. In this guide, we’ll break down the most common residential wiring cables, how they’re used, and what makes each one unique. By the end, you’ll clearly understand what kind of cable is installed inside modern homes and when each type is appropriate.

What Is Residential Wiring?
The Most Common Types of Cables
2.1 Non‑Metallic Sheathed Cable (NM / NM‑B / Romex)
2.2 Underground Feeder Cable (UF / UF‑B)
2.3 Armored Cable (AC / BX)
2.4 Metal‑Clad Cable (MC)
2.5 Conduit Wiring & Individual Wires (THHN/THWN)
Cable Selection by Location and Use
Cable Gauge, Color Coding & Ampacity
Safety, Codes & Best Practices
Common Misconceptions About Residential Wiring
Conclusion: What Cable Should You Use?
Frequently Asked Questions
References

1. What Is Residential Wiring?

Residential wiring refers to the electrical system that distributes power throughout a house — from the main panel to switches, outlets, lighting fixtures, and appliances. Unlike commercial wiring, residential circuits are usually simpler, but safety remains paramount. To comply with the U.S. National Electrical Code (NEC), specific cable types and installation methods are required for different parts of the home.

2. The Most Common Types of Cables

2.1 Non‑Metallic Sheathed Cable (NM / NM‑B / Romex)

Overview:
Non‑metallic sheathed cable — most commonly referred to as NM cable or Romex — is the dominant type used in modern residential wiring.

Key Features:

Flexible cable with two or more insulated copper conductors plus a bare ground wire.
Outer jacket of thermoplastic material (often PVC).
Most NM cables are labeled NM‑B, rated for dry indoor use.

Uses:
NM cable is used for general circuitry inside walls and ceilings — powering outlets, lights, switches, and branches from the panel.

Why It’s Popular:

Easy to install and inexpensive
Available in common gauges (e.g., 14‑2, 12‑2) for typical circuits

Limitations:
Not suitable for damp or wet locations unless installed inside conduit.

2.2 Underground Feeder Cable (UF / UF‑B)

Overview:
Underground Feeder cable (UF) is similar in appearance to NM but is designed for wet locations and direct burial without conduit.

Key Features:

Each internal conductor is individually surrounded by solid thermoplastic.
Entire cable is moisture‑resistant, making UF suitable for outdoors.

Uses:

Outdoor lighting circuits
Pool and shed power feeders
Underground runs to detached structures

Note:
While UF can be underground, specific NEC³ standards must be followed for burial depth and protection.

2.3 Armored Cable (AC / BX)

Overview:
Armored cable — often called AC or BX — has a flexible metal sheath around insulated conductors and is one of the three types of networking cables commonly used in structured cabling systems.

Key Benefits:

Added mechanical protection
Useful where NM is impractical or prohibited

Use Cases:
Often in basements, garages, or exposed ceiling areas where physical protection is desired.

2.4 Metal‑Clad Cable (MC)

Overview:
Similar to armored cable but typically with sturdier metal cladding and a separate grounding conductor.

Uses:
Residential areas where NM cable is too fragile and conduit is not desired.

2.5 Conduit Wiring & Individual Wires (THHN/THWN)

In some applications (e.g., exposed or high‑risk areas), electrical conductors are not inside cable at all but run individually inside conduit (metal or plastic) using THHN or THWN insulated wires.

THHN: Thermoplastic High Heat‑resistant Nylon‑coated
THWN: Thermoplastic Heat and Water‑resistant Nylon‑coated

The type of cable used for most modern installations is more common in commercial wiring — but sometimes used in residential garages, basements, and outdoor runs.

3. Cable Selection by Location and Use

Location	Cable Type Typical Use
Dry interior walls	NM‑B (Romex)
Outdoor wiring	UF‑B or conduit with THWN/THHN
Exposed areas	Armored (AC/BX) or MC
Underground burial	UF‑B
Garage ceilings	Conduit with THHN/THWN

Safety Tip: Always check local electrical codes and permit requirements — your municipality may have specific standards.

4. Cable Gauge, Color Coding & Ampacity

Residential circuits use specific wire gauges based on the load:

14‑gauge NM‑B → 15‑amp circuits
12‑gauge NM‑B → 20‑amp circuits
10‑gauge or larger → appliances and dedicated circuits

NM cable jacket colors commonly indicate gauge:

White: 14‑gauge
Yellow: 12‑gauge
Orange/Black: Larger circuits

5. Safety, Codes & Best Practices

The National Electrical Code (NEC) sets standards for residential wiring — including what cable types are permitted in specific locations.

Key Safety Practices:

Never use NM cable outdoors or in wet locations without protection
Use correct gauge to match breaker rating
Avoid DIY wiring beyond basic maintenance

Professional Tip: Improper cable selection or installation is a leading cause of electrical fires and code violations.

6. Common Misconceptions About Residential Wiring

“Romex is only a brand name.”
True — Romex is a trademark for NM cable, but the term is widely used in everyday speech to mean any non‑metallic sheathed cable.
“Armored cable is bullet‑proof.”
It’s tougher than NM but still must meet code and can be harder to install.
“All cables can be buried.”
Only specifically rated cables (like UF) can be buried directly without conduit.

7. Conclusion: What Cable Should You Use?

For most residential interior wiring, NM‑B (Romex) is the standard choice due to its ease and cost‑effectiveness. Outdoor or wet locations require UF‑B or conduit with THWN, while exposed areas may need armored or metal‑clad cable. Always prioritize safety and consult licensed electricians when in doubt.