The B in NM-B wire stands for “binder,” a designation that specifies the type of wire commonly used in residential buildings. NM-B wire is a type of non-metallic sheathed cable that is commonly used for indoor electrical wiring. This type of wire is specifically designed for use in dry locations and is commonly used in residential construction. The B designation indicates that the wire has a heat-resistant binder separating the conductors. This binder helps to protect the wires from damage and ensures safe and efficient electrical connections. When selecting wiring for your home, it is important to choose the appropriate type for the specific application to ensure safety and compliance with building codes.

Non–metallic sheathed cable used for electrical wiring.

Commonly used in residential and commercial buildings.

The “B” stands for Building in NM-B wire.

Has thermoplastic insulation for protection.

Rated for use in dry and damp locations.

• B stands for Building in NM-B wire.
• Non–metallic sheathed cable.
• Used in residential and commercial buildings.
• Has thermoplastic insulation for protection.
• Rated for dry and damp locations.

What Does The B Stand For In Nm-B Wire?

Why is it called NM-B wire?

NM-B wire stands for Non-Metallic Sheathed cable with a B rating. It is commonly used for residential wiring and is designed for indoor use in dry locations. The “B” designation indicates that the wire is suitable for use in dry locations.

• NM-B wire is commonly used for wiring outlets, switches, and light fixtures in homes.
• The “B” rating signifies that the wire has a temperature rating of 90 degrees Celsius.
• It is important to follow local building codes and regulations when using NM-B wire.

What is the difference between NM and NM-B wire?

NM-B wire is an updated version of NM wire that includes a B rating. The B rating indicates that the wire is suitable for use in dry locations and has a higher temperature rating.

NM Wire	NM-B Wire
Not suitable for dry locations	Suitable for dry locations
Temperature rating of 60 degrees Celsius	Temperature rating of 90 degrees Celsius

Where can NM-B wire be used?

NM-B wire can be used in various residential applications, including wiring outlets, switches, and light fixtures in dry locations. It is commonly used in new construction and renovation projects where wiring needs to be installed.

• It is important to consult local building codes to ensure compliance with regulations when using NM-B wire.
• NM-B wire should not be used in areas where it may be exposed to moisture or wet conditions.

When should NM-B wire be used?

NM-B wire should be used when wiring is required in dry locations, such as interior walls and ceilings. It is suitable for use in residential applications where wiring needs to be concealed within the structure.

Use in dry locations	Avoid use in wet or damp areas
Interior walls and ceilings	Avoid direct exposure to sunlight

Who determines the standards for NM-B wire?

The standards for NM-B wire are determined by organizations such as the National Electrical Code (NEC) and the Underwriters Laboratories (UL). These organizations set guidelines and requirements for the safe installation and use of electrical wiring.

• Compliance with NEC and UL standards is essential to ensure the safety and reliability of electrical systems.
• Manufacturers of NM-B wire must meet these standards to obtain certification for their products.

How is NM-B wire different from THHN wire?

NM-B wire is designed for use in residential applications and is suitable for dry locations. In contrast, THHN wire is primarily used in commercial and industrial settings and is suitable for both dry and wet locations.

NM-B Wire	THHN Wire
Residential applications	Commercial and industrial settings
Dry locations	Dry and wet locations

Which gauge sizes are available for NM-B wire?

NM-B wire is available in a range of gauge sizes to accommodate different electrical requirements. Common sizes include 14, 12, and 10 gauge, with larger gauges indicating thicker wire.

• Smaller gauge sizes, such as 14 gauge, are suitable for lighting circuits and general outlets.
• Larger gauge sizes, such as 10 gauge, are used for appliances and high-power devices.

What are the color codes for NM-B wire?

NM-B wire follows specific color codes to indicate the purpose of each wire within the cable. The most common color codes for NM-B wire are white, black, and red, which signify neutral, hot, and switched hot wires, respectively.

Color	Purpose
White	Neutral
Black	Hot
Red	Switched Hot

Can NM-B wire be used in outdoor applications?

NM-B wire is not suitable for use in outdoor applications where it may be exposed to moisture or wet conditions. It is designed for indoor use in dry locations and should not be used outside without adequate protection.

• For outdoor wiring, consider using UF-B wire, which is specifically designed for underground and outdoor applications.
• Always consult local building codes and regulations before installing electrical wiring outdoors.

Is NM-B wire suitable for use in conduit?

NM-B wire is not designed to be used in conduit due to its rigid and insulated nature. Conduit is typically used with THHN wire in commercial and industrial applications where additional protection is required.

NM-B Wire	THHN Wire
Not suitable for conduit	Commonly used in conduit
Rigid and insulated	Flexible and durable