What Is Romex Wire?
Romex is the widely recognized brand name for Type NM-B (Non-Metallic Sheathed) cable, the standard electrical wire used in residential construction throughout the United States. Manufactured by Southwire, the Romex brand has become so ubiquitous that electricians and homeowners use the name generically to refer to any NM-B cable, similar to how “Band-Aid” refers to adhesive bandages regardless of brand. NM-B cable from any manufacturer serves the same purpose and meets the same code requirements.
What Romex Looks Like
Romex cable consists of two or three insulated copper conductors (typically with black, white, and red insulation) plus a bare copper ground wire, all wrapped inside a flat or oval plastic outer jacket. The jacket color indicates the wire gauge inside. White jacket contains 14 AWG conductors (rated for 15-amp circuits). Yellow jacket contains 12 AWG conductors (rated for 20-amp circuits). Orange jacket contains 10 AWG conductors (rated for 30-amp circuits). Black jacket typically contains 8 AWG or 6 AWG conductors (rated for 40-amp or 50-amp circuits).
The cable is labeled with its specifications printed on the outer jacket. For example, “14/2 WITH GROUND NM-B” indicates 14 AWG wire, 2 insulated conductors plus a ground, Non-Metallic sheathed type B cable.
Common Uses for Romex
General Outlet and Lighting Circuits
The most common Romex application is wiring outlets and light fixtures throughout a home. 14/2 NM-B on 15-amp circuits handles general lighting and bedroom outlets. 12/2 NM-B on 20-amp circuits is required for kitchen countertop outlets, bathroom outlets, garage circuits, laundry circuits, and outdoor receptacles.
Three-Way Switch Circuits
When a light fixture is controlled by two switches (such as at both ends of a hallway), 14/3 or 12/3 NM-B cable provides the extra conductor (red) needed for three-way switch wiring.
Dedicated Appliance Circuits
Larger Romex sizes serve dedicated appliance circuits. 10/3 NM-B is standard for electric dryer circuits (30A/240V). 10/2 NM-B is used for electric water heaters (30A/240V). 8/3 or 6/3 NM-B serves electric ranges and cooktops (40A or 50A/240V).
Where Romex Cannot Be Used
NM-B cable is restricted to dry, interior locations that are protected from physical damage. Romex cannot be used outdoors or in any location exposed to weather. It is not permitted in wet or damp locations including most basements in some jurisdictions. NM-B cannot be installed in conduit in most cases (individual THHN conductors are used in conduit instead). It is not permitted for exposed runs in commercial buildings. Romex cannot be used for direct burial underground (UF-B cable is required for underground installations). Some jurisdictions, most notably Chicago, prohibit NM-B entirely and require all residential wiring to be run in conduit.
Romex vs. Other Wire Types
Romex (NM-B) is one of several wire types used in construction. THHN/THWN is used for individual conductors in conduit. UF-B is the underground-rated version of residential cable. SER/SEU is used for service entrance feeds. MC (Metal Clad) cable is an armored alternative to NM-B that provides physical protection and is permitted in more locations. Each type serves specific applications defined by the NEC.
IB Lighting carries Romex (NM-B) cable in all standard sizes from 14/2 through 6/3, in spool lengths from 25 feet to 1,000 feet. Call (800) 674-9019 for pricing and bulk availability, or browse our electrical wire inventory online.