Home » FAQs » Type NM-B (Romex) Cable

Table of Contents

  1. Introduction
  2. Overview of Type NM-B Cable
  3. Features and Specifications
  4. Installation Guidelines
  5. Advantages of Type NM-B Cable
  6. Applications of Type NM-B Cable
  7. Safety Considerations
  8. Maintenance Tips
  9. Conclusion


Type NM-B (Romex) cable is one of the most commonly used electrical cables in residential and commercial buildings.
Its popularity stems from its ease of installation, versatility, and cost-effectiveness. In this comprehensive guide,
we will explore the features, installation guidelines, advantages, applications, safety considerations, and maintenance
tips for Type NM-B cable.

Type NM-B (Romex) Cable

Overview of Type NM-B Cable

Type NM-B cable, also known as Romex cable, is a non-metallic sheathed cable primarily used for indoor electrical wiring.
It consists of two or more insulated conductors, usually color-coded, and a bare copper grounding conductor. The conductors
are encased in a moisture-resistant PVC jacket, providing protection and insulation. NM-B cable is available in various
gauges to accommodate different electrical loads.

Features and Specifications

Type NM-B cable offers several notable features and specifications, including:

  • Non-metallic sheathing for flexibility and ease of installation.
  • Color-coded insulated conductors for easy identification.
  • Bare copper grounding conductor for safety.
  • Moisture-resistant PVC jacket for protection against environmental factors.
  • Rated for specific amperage and voltage requirements.
  • Available in different gauges, such as 14, 12, and 10 AWG, to support various electrical loads.

Installation Guidelines

Proper installation of Type NM-B cable is crucial to ensure electrical safety and code compliance. Here are some general
installation guidelines to follow:

  1. Plan the electrical circuit and determine the cable length required.
  2. Turn off the power supply to the area where the installation will take place.
  3. Choose the appropriate cable gauge based on the electrical load.
  4. Route the cable through the designated path, ensuring it is not exposed to potential physical damage or excessive heat.
  5. Secure the cable using appropriate staples or straps, maintaining the required spacing.
  6. Strip the cable sheathing and strip the insulation of the individual conductors.
  7. Connect the conductors to their respective terminals or devices, following the appropriate wiring diagrams or instructions.
  8. Properly ground the cable by connecting the bare copper grounding conductor to grounding points or devices.
  9. Use approved connectors or termination methods to ensure secure and reliable connections.
  10. Test the installed circuit using appropriate testing equipment to verify proper functionality.
  11. Finally, restore the power supply and conduct a final inspection to ensure compliance with electrical codes and regulations.

Advantages of Type NM-B Cable

Type NM-B cable offers several advantages that contribute to its widespread use in electrical installations:

  • Easy installation: The non-metallic sheathing of NM-B cable makes it flexible and easy to work with, simplifying the installation process.
  • Versatility: NM-B cable is suitable for various residential and commercial applications, including lighting, outlets, and appliances.
  • Cost-effective: Compared to other wiring options, NM-B cable is relatively affordable, making it a budget-friendly choice.
  • Time-saving: The ease of installation and simplified wiring process can save significant time during electrical projects.
  • Code compliance: Type NM-B cable meets the requirements of electrical codes and regulations when installed correctly, ensuring safety and adherence to standards.

Applications of Type NM-B Cable

Type NM-B cable finds extensive use in various electrical applications, including:

  • Residential wiring: NM-B cable is commonly used for residential electrical wiring, providing power to outlets, lighting fixtures, and appliances throughout the house.
  • Commercial buildings: From small offices to large commercial spaces, NM-B cable is suitable for powering electrical systems in commercial establishments.
  • Renovations and additions: Whether it’s a home renovation or an additional room, NM-B cable can efficiently supply electricity to new circuits or extend existing ones.
  • Outdoor installations: While NM-B cable is primarily intended for indoor use, it can also be used for certain outdoor applications where the cable is protected within conduit or buried underground.

Safety Considerations

When working with Type NM-B cable, it is essential to prioritize safety. Consider the following safety guidelines:

  • Ensure the power supply is turned off before starting any installation or maintenance work.
  • Handle the cable carefully to avoid damaging the insulation or conductors.
  • Follow proper grounding procedures to minimize the risk of electrical shocks and provide protection against faults.
  • Use appropriate protective equipment, such as gloves and safety glasses, when handling and working with the cable.
  • Adhere to local electrical codes and regulations to ensure compliance and safety.
  • If unsure about any aspect of the installation, consult a qualified electrician or seek professional advice.

Maintenance Tips

To ensure the longevity and reliability of Type NM-B cable installations, consider the following maintenance tips:

  • Regularly inspect the cable for any signs of damage, such as fraying, cuts, or exposed conductors.
  • Check the cable connections periodically to ensure they are secure and free from corrosion or loosening.
  • Keep the cable free from excessive heat sources or direct sunlight, as prolonged exposure can degrade the insulation.
  • Prevent the cable from being pinched, crushed, or subjected to excessive bending, as this can damage the conductors.
  • Avoid overloading circuits beyond their rated capacity to prevent overheating and potential hazards.
  • In case of any electrical issues or abnormalities, promptly address them to prevent further damage or safety risks.
  • Consider periodic professional inspections to ensure the integrity and safety of the NM-B cable installations.


Type NM-B (Romex) cable is a versatile and cost-effective solution for electrical wiring in residential and commercial buildings.
Its ease of installation, flexibility, and adherence to electrical codes make it a popular choice among electricians and homeowners.
By understanding the features, installation guidelines, advantages, applications, safety considerations, and maintenance tips of
Type NM-B cable, you can ensure safe and reliable electrical installations in your projects. Always prioritize safety and consult
professionals when needed to ensure code compliance and optimal performance of your electrical systems.

Published On: 2023年7月4日Categories: ,