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Consequently, it’s a common wiring method for residential and commercial branch circuits. Because it provides minimal physical protection for the conductors, the installation restrictions are strict. Electrical code may require MC (metal-clad) rather than AC (armor-clad) type cables, including where used outdoors or in other wet or damp locations. Often small pieces of metal will break off and they can be very sharp. BX is as good as NM cable from a Magnetic Field standpoint but has the added benefit of shielding Electric Fields . The metal sheathing absorbs the electric fields emitted by the wires and shunts it to ground. The plastic sheathing of NM cable does not shield electric fields.
I understand the code language, but even at my local suppliers there is confusion as what product is what. If I ask for armor cable, I will virtually always get a roll of MC cable. The National Electrical Code prohibits use of BX ( technically named Armored Cable/AC ) in wet locations. Use metal-clad with a metal bx cable definition sheath specifically listed as impervious to water, or underground feeder/branch circuit cable , either by itself or in a conduit system approved for use in wet locations . Electrical cable encased in metal sheathing is often used in basements and other areas where the wire is not encased in a finished wall.
These cables can be installed either indoors oroutdoors and in exposed and concealed locations. AC90 is a flexible interlocked aluminum armoured cable approved for use in open and concealed wiring in dry locations. This type of MC Cable will have a continuous PVC outer jacket. These cables are used as lift cables bx cable definition and trailing cables in railways, ship wiring and many others. In our range of Armoured Electric Cables, we also provide multi core flexible screen cables and multi core flexible instrumentation armoured cables. An electrical cable also has different types, color and application as its determining factors.
Here’s a brief about cables that you need to understand to determine the correct cable for your home. I’ve been in many attics where the armor was glowing red because the insulation had failed on a couple of conductors in different places. The short doesn’t draw enough current to trip a breaker but does heat the armor, sometimes to a bright red, but more often to a red you can see only in the dark. This situation, when present, also causes faster deterioration of any “good” insulation present between the fault points.
How To Use Armored (bx) Electrical Cable
Cut a 20 centimeter (7.9 in) length of the armor using either a hacksaw or a rotary cutter designed for the purpose. When the cut is nearly through, grab the cable jacket above and below the cut and twist sharply – this should break the remaining armor without the need for the saw to contact the wires inside. Use caution – the bx cable definition metal edges are sharp.Carefully inspect the interior insulation to make sure none of the conductors have been exposed by nicks or gashes. If there is damage, you may need to try again by moving back and redoing another cut. BX CableNM CableRippingBX is difficult to rip back without a special tool.NM is far easier to rip back.
Early NM cable had their individual conductor insulation wrapped in a cotton braid that was impregnated with either a varnish or tar-like substance for moisture protection. Around 1950, synthetic spun rayon was being permitted to replace the cotton thread in the jacket braid. Then in the early 1960’s, thermoplastic began replacing the braided jacket altogether, and by about 1970, most all NM cable had a compounded PVC outer jacket, even though a braid was still permitted until 1984. Also in 1984, NM-B cable was developed and required to have 90°C rated individual conductors, and a 75°C outer jacket. Now AC cable cannot be used in exterior or damp locations. Where MC Cable may be used in exterior applications but must be suitable for exterior or direct burial.
Nec Revisions For Cable
How long does Romex last?
Today’s romex should last at least 400 years.
Just another of the many reasons why it is so important to consider the precision of code language when describing a condition, method, citation, etc. So to answer your question – Yes just have them install a grounding tail from the metal box to the devcie. Following the proper bending radius may bx cable definition change the enclosure sizing or layout for the project, so be sure to read the entire cable article. Identify the type of cable under consideration by its Chapter 3 Article name . A new Informational Note in 338.10 alerts Code users to Table 310.15 for SE cables used as a main power feeder.
The informational note does direct the NEC user to ANSI Z535.4 2011, Product Safety Signs and Labels, which provides guidance for suitable font sizes, words, colors, symbols and location requirements for labels. The text size in a warning label and the location are based on many factors including, but not limited to, the intended viewer and to ensure a safe viewing distance. These colors, while not specifically addressed in the NEC, are universally understood and must be adhered to for field-applied warning labels. Making labels on your own without following these guidelines could subject the label-maker to future liability concerns.
Is Mc Cable Considered Conduit?
Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code , Jim will help you solve it. Questions can be sent to https://personal-accounting.org/ Answers are based on the 2014 NEC. So “BX” is defined as “AC” cable and “MC” is defined as Metal Clad cable. These two cable assemblies are very similar in construction.
Here is another reason to use BX over NM cable that can save you well over $1,000. BX is resistant to nails and screws and rodents and other pests. If you have to tear out a wall to replace a wire that has been punctured by a nail, supposing you were hanging a picture, this repair could cost well over $1,000. If the conduit used is PVC, the benefits are the same as NM cable, low Magnetic Fields but no Electric Field shielding. If the conduit used is galvanized steel, the benefits are the same as BX, good resistance to puncture, low MF emittance, and good EF shielding.
The original AC cable, AC-90® is designed for most commercial, industrial and multi-residential branch circuits, services for power, lighting, control and signal circuits. An additional AC cable that AFC developed was introduced and called AC-Lite®.
What Type Of Wire Is Used Outside?
The National Electrical Code and Local Building Codes regulate the manner of installation and the types of wires and cables for various electrical applications. Additionally, with the armor wound around the conductors, a ground fault current could create a choke coil effect on the conductors within the outer armored sheath, leading to greater problems. Individual conductors run inside conduit is used primarily in industrial and commercial applications, and is rarely used in residential wiring.
This is simply a variation of the AC-90® but instead utilizes an aluminum armor. 12/2 is used for 20-amp circuits and 14/3 wire has 2 “hot” wires and is rated for 15-amp circuits. You can easily find spools of BX cable up to 1,000 feet long. The actual gauge for your project will depend upon the length and the operating load to be fed at the far end. Insert a BX connector over the end of the newly cut armor and tighten the screw to secure it to the armor. Many inspectors will want to see the “listing label” for your cable so they can verity that it conforms to the code requirements and standards for cable construction. Be sure to obtain any necessary electrical permits, even if your jurisdiction allows the work to be done by a non-licensed electrician.
I am not trying to win anything, I am simply trying to get the man do become a productive member of this board and get his head out of that dark hole down there. Finally, in 1962 the Code was revised to require all branch circuits to include a grounding bx cable definition conductor or ground path to which the grounding contacts of the receptacle must be connected. One really has to stop and be intentionally specific to make sure one is discussing the correct wiring method so as to cite the proper provision of code.
- BX are usually ground through the sheath; this is why BX cables most often need to be buried.
- BX’s armor, while much stronger than NM’s vinyl, can still be pierced by a determined and ill-placed nail or screw.
- However, with the exception of electrical wires that run through rigid metal conduits, no other type of electrical cable has as strong an outer casing as does BX cable.
- Like any other cable, if the armor is nicked, cut, or shredded, the wires inside can be compromised.
As a do-it-yourself residential electrician, you likely will find it easier to handle, rip, and pull NM, or Romex brand, electrical cable. Unless the specifics of the job or the electrical code demand that you use BX cable, your wiring project will go faster with NM, plastic-sheathed wiring. With this method, there is the danger of nicking the insulation on the inner wires, not to mention lacerating your fingers on the sharp metal armor.
Metal-clad cables are typically galvanized steel or aluminum interlocking cable. And some companies’ armored cables, such as Mencom, use a woven flexible stainless-steel design. A variety of armored cable designs from Mencom Corp.Armored cables feature some type of metal sheath that is the first layer of armor. It is usually made of interlocking or continuous aluminum or stainless steel, or it can be covered in a smooth or corrugated metal tape. According to Mencom, which uses a stainless-steel design, the armor protects the cable inside from water damage by high-pressure washdown, cleaning agents and extreme temperatures. When transmitting data or conducting power in harsh environments, protecting your cables is crucial to safe and reliable operation.
If you require wiring for wetlocations, you must use THWN wire. It’s important tonote that now many wires in the market are dual rated bothTHHN and THWN, which means the wire can be used indry, damp, or wet locations. Type AC cable is a factory assembly of insulatedconductors protected in an overall flexible interlocked metallicarmor . Armored cable having an aluminum sheath issuitable for use in alternating current circuits only.
The ColorSpec® ID system these cables are designed with is intended to help in identifying flexible armored cable at a distance. The AC-90® steel cable comes with a black armor, AC-Lite® with plain silver armor, and HCF-90® cables come with green armor. In addition, all AFC AC cables come with phase identification painted directly onto the armor for added identification without the added step of opening up the panel to determine phase voltage. Conductors are insulated with moisture and fire retardant paper wrap that meets all applicable OSHA and HUD requirements.
The exception allowing the uninsulated conductor to be used as the neutral in pre-existing installations has also been revised to clarify that this practice is allowed only in certain existing applications. If you install multiple Type NM cables in contact with thermal insulation without maintaining spacing between cables, then you must adjust the allowable ampacity of each conductor per Table 310.15, as shown in Fig.
It was originally called “Greenfield Flexible Steel-Armored Conductors,” after one of its inventors, Harry Greenfield. FEN Learning is part of Sandbox Networks, a digital learning company that operates education services and products for the 21st century. If you expect to be doing a lot of cutting, you may wish to invest in a special BX cutter, such as the Roto-Split. This tool costs between $20 and $50 and makes the job of splitting and ripping back BX cable far easier and safer than by hand.
After you insert the cable into the tool’s groove, you turn the handle to cause the cutting wheel to cut away the metal sheathing. The tool is calibrated to cut the metal but stops short of touching the inner wires. When doing electrical projects on your home, generally you will be using NM, or non-metallic, electrical cable as it is easy to handle and inexpensive. But occasionally you might open up a wall or ceiling and encounter a type of metal-clad cable called BX.
Better yet, use a special armored cable cutting tool.NM cable can be cut with a lineman’s pliers or even with the cutter on a wire stripper.CodeBX is accepted by the National Electrical Code . Older BX cables without an internal bonding strip are not accepted by NEC.NM cable is also accepted by the NEC. BX’s metal sheathing runs in a helix-like or twisted manner around the wires.
