Umair Gaines
In electrical wiring, NM stands for non-metallic and refers to a type of cable with a vinyl or PVC outer sheathing. It is used for residential electrical devices and is the most common wiring used when wiring a house. NM cables are made of copper and are individually coated in plastic. They are typically used for GFCI outlets, lights, and wall outlets. NM cables are also known as Romex wire, which is the brand name of one type of NM wire.
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What You'll Learn
NM stands for non-metallic
Non-metallic wiring is typically made up of three parts: an outer cable sheathing, wire insulation, and individual wires (conductors). The outer sheathing is made of a tough 30 mil-thick PVC jacket that serves to protect the bundle of individual wire conductors. The wires within the sheathing are made of soft, uncoated copper and are individually coated in plastic. A strip of paper is often woven between the individual wires to act as a separator.
NM cable comes in various wire gauges, with 12-gauge and 14-gauge wires being the most common for standard household circuits. The size of the conductors and their number are used to identify the type of NM cable. For example, the commonly used Type NM 12-2 cable contains two 12 American Wire Gauge (AWG) insulated conductors.
NM cable is permitted for use in one and two-family dwellings, including their attached or detached garages and storage buildings. However, it is not suitable for services, outdoor use, underground installation, embedding in concrete, or as data or fire alarm cable. NM cable should be secured at intervals not exceeding 4.5 feet and within 12 inches of junction boxes and panels to prevent sagging and vulnerability to damage.
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NM cables have vinyl/PVC outer sheathing
NM stands for non-metallic, referring to the outer sheathing of the cable. NM cables are electrical wires with an outer sheathing made of PVC. The sheathing bundles the individual wires into a cable. The wires within the sheathing are typically made of copper and are individually coated in plastic.
NM cables are commonly used for residential wiring of lighting fixtures, outlets, and appliances. They are suitable for use in dry areas like walls and ceilings. The cable's outer sheathing is made of a tough 30 mil-thick PVC jacket that protects the bundle of individual wire conductors. The PVC material is resistant to wear and tear and provides a protective layer that prevents electrical currents from leaking out and making contact with other objects.
The colour of the NM cable sheath can indicate the gauge of the current-carrying conductors within it or special properties of the sheathing itself. For example, an NM cable containing 14-gauge conductors uses a white outer jacket, while a cable with 12-gauge conductors uses a yellow outer jacket.
NM cables are available in various types, each tailored to specific uses such as linking devices for computer networks, data transfer, cable TV, and telephone systems. They are popular for residential and light commercial applications due to their durability, longevity, and high performance.
It is important to note that NM cables are not suitable for heavy-duty applications as extreme temperatures can easily damage them.
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NM cables are used for residential wiring
NM stands for non-metallic, and it refers to a type of electrical wiring with a non-metallic outer sheathing. This outer coating is made of PVC and is typically 30 mil thick. NM cables are frequently used in residential wiring for lighting and outlets. They are suitable for indoor applications in dry areas like walls and ceilings.
NM cables are commonly used in homes to wire circuits for lighting fixtures and wall outlets. They are also used for residential electrical devices such as GFCI outlets and lights. NM cables are suitable for use in normally dry locations and can be installed in air voids, joints, and masonry block or tile walls that are not exposed to excessive moisture or dampness.
NM cables are available in various types, each tailored to specific uses. For example, they can be used for linking devices for computer networks, data transfer, cable TV, and telephone systems. NM cables are also suitable for low-voltage tasks, such as connecting a router to a printer.
NM cables are a popular choice for residential wiring due to their ease of installation and flexibility. They are also cost-effective and widely available. However, it's important to note that NM cables have weak moisture resistance and are not suitable for heavy-duty applications or extreme temperatures.
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NM cables are rated 600-volt for exposed and concealed work
NM stands for non-metallic cable, also known as Romex wire or cable. It is a type of electrical wire or cable with an outer sheathing made of PVC that bundles together the individual wires inside. These wires are typically made of copper and are individually coated in plastic.
NM cables are commonly used for residential wiring of luminaries, devices, and appliances. They are suitable for dry locations and are rated for 600 volts for both exposed and concealed work. This means that NM cables can be used in areas that are not completely enclosed or hidden, as well as in walls or other concealed spaces.
The specific type of NM cable used for 600-volt applications is typically NM-B. This type of cable is designed for use in normally dry locations and has an ampacity limitation that must be followed in accordance with the 60ºC conductor temperature rating specified in the NEC (National Electrical Code).
It is important to note that NM cables are not suitable for all applications. They are prohibited from use in hazardous locations and should not be embedded in concrete. Additionally, older NM cables that used aluminum or copper-jacketed aluminum are no longer allowed by code, and only pure copper wires are now used in residential wiring.
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NM cables are secured at intervals not exceeding 4.5 feet
NM, or non-metallic cable, is a type of electrical wiring commonly used in residential buildings. It is composed of individual copper wires, each coated in plastic, which are bundled together within an outer sheathing made of PVC. This outer sheathing is typically 30 mil-thick and serves to protect the individual wire conductors.
When installing NM cables, it is important to secure and support them adequately to prevent sagging and potential damage. According to the National Electrical Code (NEC), specifically NEC 334.30, NM cables must be secured and supported at intervals not exceeding 4.5 feet (1.4 meters) and within 12 inches (300 mm) of every cable entry into enclosures such as outlet boxes, junction boxes, cabinets, or fittings. This rule ensures that the cable does not put strain on terminations and joints, reducing the risk of electrical failures or hazards.
The NEC provides specific guidelines for securing and supporting NM cables to ensure compliance and safety. Installers may use staples, cable ties, or straps that are designed and installed in a way that does not damage the cable. It is important to note that flat cables, such as 12/2 and 14/2 NM-B, should not be stapled on edge to prevent crushing the conductors together.
Additionally, when installing NM cables horizontally through holes or notches in framing members, it is considered supported and is not required to be secured. Similarly, when NM cables are fished within walls, they do not need additional support or fastening. However, in accessible ceiling dwelling units, support for the cable should be within 4.5 feet of the last point of support to a connection with a luminaire or other electrical equipment.
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Frequently asked questions
NM stands for non-metallic and refers to a type of electrical cable.
An NM cable is a non-metallic sheathed cable. It is made up of insulated conductors within a non-metallic jacket. NM cables are used for residential wiring of luminaries, devices and appliances.
There are three main types of NM cables: NM, NMC, and NMS. NMC has a corrosion-resistant outer covering, while NMS contains communications (signaling) wires in addition to the usual power conductors.
NM cables should be secured and clamped to device boxes, junction boxes, and fixtures. They should not be left unsupported as this can cause them to sag and become vulnerable to damage. NM cables are also not permitted in residential construction higher than three stories or in any commercial construction.
