Which wiring method is commonly used for residential branch circuits?

Non-metallic sheath cable, commonly referred to as NM cable or Romex, is the standard wiring method used in residential branch circuits due to its versatility, ease of installation, and cost-effectiveness. It consists of insulated conductors enclosed in a non-metallic sheath, which protects the wires while allowing for flexibility in routing through walls, attics, and other spaces. This type of cable is specifically designed for indoor use in residential applications and is suitable for various residential loads, including lighting and general-purpose outlets.

The design of NM cable also facilitates quick installation, as it can be run without the need for conduit in most circumstances, reducing labor time and expense. Additionally, its non-metallic covering helps to protect against moisture and physical abrasion, making it suitable for residential environments.

In contrast, other wiring methods like single-conductor cables and flexible armored cables have specific uses where wire exposure or additional durability is needed, while metal conduit is more commonly used in commercial settings or areas requiring additional protection from physical damage and environmental conditions. Therefore, NM cable remains the preferred choice for residential branch circuits.