More colored wires can also complete an electric cable such as blue, yellow, orange, used as travelers on 3-way and 4-way switches or as switch legs when wiring ceiling fans, lights, and switched outlets. BX cabling costs more to install, and some electricians may belly-ache about using it because it is heavier and slightly more cumbersome to work with, but if I were to build a new home, it would consider essential. There are several types of these cables that you can install in exposed locations, including outdoors and indoors. It is the opposite of NM cables that you can install in enclosed environments.
One final distinction is that MC cables don’t have a limited number of conductors they can contain, while AC cable can contain no more than four insulated conductors. What MC and BX have in common is their basic armored structure, which means that its individual conductors are better protected than NM and similar cable. Both are sometimes simpler to install that wire in conduits, which reduces the cost. BX cable can, by some estimates, be 35-40% more expensive than NM (via Healthy Building Science), yet still be cheaper to install overall. BX cable comprises plastic-coated insulated wires of about 12- or 14-gauge rolled up together and protected using a ribbon-like metal sheathing.
Forums General Topics of the Trade General Discussion Area Romex vs. BX or MC cable
This is a major advantage for BX, but the savings probably mostly apply to MC cable as well. Typical residential MC and AC installations start after wall-framing with careful planning and layout, beginning with home-runs from the load center (circuit breaker box), says the National Armored Cable Manufacturers Association. The average residential installation is basically similar to standard Romex, except that obviously the support fittings, connectors, etc. are different. Cable may be routed through wall studs and certain dry structural spaces, such as within masonry air space gaps.
- Warshauer Electric Supply hosts a very thorough lexicon of electrical industry jargon and slang, from which you learn that electricians are a colorful lot and that they seem to have a tenuous grasp on human anatomy.
- For instance, if you want to strip insulation from a 12-gauge wire, you should select the hole that is labeled ’12’.
- Finally, AC cable is limited to four conductors, while MC is not limited.
- Perhaps your home still contains knob and tube, or you are considering remodeling or planning new construction.
Your choice of cable depends on the requirements of your project and your skill level and experience. The flexible metal sheathing is easy to install, about as easy as NM cable. It resists puncture by nails and screws, and, as I will describe later, is more resistant to being chewed through by rodents and other pests than NM cable and knob and tube. Southwire’s MCAP product, a metal-clad cable which uses its armor for grounding, is $238 for the same specs at Home Depot. Southwire offers a calculator to demonstrate the supposed labor savings that justify the simpler installation of MCAP versus standard MC wire, which involves one fewer termination per electrical box. Assuming a home uses 10 circuits (via D&F Liquidators) and 10 outlets, plus another five terminations for switches and light fixtures (via REthority), the calculator estimates $625 in savings for all 150 termination points.
An example of this is the use of the grounding conductor (and therefore the armor itself) as a neutral conductor rather than a ground — an inexpressibly dangerous mistake. McCurdy says that the insulation, wraps, anti-short bushings, bonding wire, and galvanizing process of the early BX cable have all been improved and are as safe today as other approved cables. The wire is protected by 2 layers of insulation, with each individual conductor being insulated and the entire bundle also being insulated. This makes insulation failure a rare occurrence and reduces the risk of accidental electrocution and arcing.
What Does NM (Non-Metallic) Electrical Cables Involve?
The city only started allowing Romex use a few years back and I think I’ve done 1 job with it. It’s tough to teach an old dog new tricks and there is still a prejudice against Romex here among electricians and homeowners alike. I’ve been considering it’s use and figured I’d look for opinions from guys who have been using it a long time about it’s advantages and disadvantages to BX.
Finally, you can add cable supports such as brackets, clamps, and staples.
BX wire has a metallic protective covering used mainly in areas where the wire is outside a finished wall and acts as an electrical conduit. In addition, both Romex and BX have plastic-coated insulated copper wires. Modern BX cable has a plastic-covered ground wire, while Romex has a bare copper ground wire. BX is as good as NM cable from a Magnetic Field (MF) standpoint but has the added benefit of shielding Electric Fields (EF). The metal sheathing absorbs the electric fields romex vs bx emitted by the wires and shunts it to ground.
Wire Insulation
To determine its properties as a conductor, the armor must be stretched out to its uncoiled full length, as the interlocking edges are not considered a strong enough electrical link. Whether you’re a DIY enthusiast or working with a professional electrician, understanding these differences ensures your wiring choices are both safe and cost-effective. A well-informed decision not only safeguards your home but also provides peace of mind for years to come. If you want to make a connection with any device, the cable sheathing is reaped using a cable ripper.
What Is BX Wiring?
- While NM cable is cost-effective and sufficient for most residential applications, BX cable offers superior protection and is essential in areas prone to physical or environmental stress.
- Like all the other cables, if you cut, shred or nick the armor, the wires found inside can become compromised.
- Different forms and types of BX cables can still be found by people renovating their homes.
- During that time, BX electrical cable was promoted as a modern, safe, and fireproof alternative to older cloth-sheathed wiring, contributing to its popularity and extensive use in various electrical projects.
NM cables can be effortlessly cut, stripped, and pulled through stud holes, making them a convenient option. BX wires are a type of metal-clad electrical cable that has been a popular choice for homeowners in the past due to its durability and added protection. Running electric cables from the electrical panel to devices like outlets or switches is crucial to any electrical project.
The tool is designed and calibrated to cut metals but stops getting in touch with inner wires. Records indicate that BX cable was first used around 1910, with widespread production and adoption taking off in the 1920s. During that time, BX electrical cable was promoted as a modern, safe, and fireproof alternative to older cloth-sheathed wiring, contributing to its popularity and extensive use in various electrical projects. Besides the ground wire to provide GND connection BX cables can also be grounded through the metal sheathing by tightening it inside a metal cable connector providing the junction box is metal. The label Romex comes from “Rome Cable Corp” which originally produced the cable for the first time.
Nowadays BX cables are also referred to as MC, type AC, armored cable, and Greenfield cables. Sometimes referred to as “Romex”, NM cable stands for “non-metallic” cable. Romex cables are composed of 2 or more insulated wires and one bare wire used for the ground connection. Both types of cable are very popular with DIYers because they are easy to work with and can be used in many applications without the need for metal conduit (if allowed by the building code and inspectors).
BX provides all the advantages of NM cable plus some additional benefits. Those wires are then again wrapped around with a metal interlocking ribbon spiraling around the wires to cover the full length of the now shielded cable. This type of sheathing where a specially profiled winding partly wraps over the previous one locking the two together in a loose manner gives the shield some flexibility to make it more pliable to work with. “BX cable” is the sort of term most homeowners will only hear about in passing. “What you have in there is BX cable,” a contractor might say, “so you need all new wiring, plumbing, and a new roof.” When you try to look it up, it appears to refer to at least a couple of completely different things.
BX cable shares a lot of characteristics (and, therefore, many pros and cons) with MC cable, as well as many restrictions of use with NM cables like Romex. BX cable is armored, and that obviously improves its resistance to puncture by nails and screws. Assuming its bend radius is observed carefully, an NEC-compliant install of BX is unlikely to be damaged during normal use. It can be purchased in spools and pulled directly without the added labor of cutting, bending, and installing conduit, and can be used in areas where conduit is not allowed or is not practical, according to JP McCurdy. BX can be installed in exposed interior locations, and it can include additional insulated grounding conductors, making it useful in healthcare and other situations where redundancy is required. To understand any cable, including BX, the first step is knowing what a cable is in the first place, and where better to look for definitions than a dictionary?
Pros and Cons of Romex Wiring
It’s therefore essential to only buy and use BX cables if either the task or the electrical codes require you to do so. Different forms and types of BX cables can still be found by people renovating their homes. However, some attribute it to being produced first in New York’s Bronx borough. Like all the other cables, if you cut, shred or nick the armor, the wires found inside can become compromised. Although a BX armor is more potent than NM vinyl, it can still be pierced by an ill-placed and determined screw or nail.