BX wiring emerged in the early 20th century for residential and commercial applications. Homeowners renovating their properties may still encounter these early forms of BX cable. The origin of the term “BX” remains uncertain, but it might be related to the product’s initial production in the Bronx borough of New York. This metal-clad cable is contrasted with newer non-metallic (NM) cables, such as the popular Romex brand, which has a slick vinyl covering, making it easier to rip and pull through holes in studs. BX is sheathed in a flexible metal spiral made either from aluminum or galvanized steel.
NM (Non-Metallic) Cables
It would be best to start by cutting across the armor, excluding the spiral. This is why I always use BX on my own jobs and recommend it on any project in which I am consulting. See the earlier blog on knob-and-tube common Residential Wiring Errors here. If the conduit used is PVC, the benefits are the same as NM cable, low Magnetic Fields (MF) but no Electric Field (EF) shielding.
After ripping, you can cut the remaining sheathing using scissors, a wire stripper, or a utility knife. Or click the button below, tell us a little about your project and let our environmental consultants help you create a healthier building. NM cable is flexible, heat & fire resistant, easy to install, and relatively inexpensive. Although NM cables are better suited for general wiring than BX, there are certain situations where some cables cannot benefit from the wall enclosure to protect them resulting in partial or total exposure to potential hazards. In such situations, the Bx can offer one of the best available solutions.
Even if you don’t have a BX cutting tool, it’s still possible to rip and cut the BX armor. Then, you can proceed to cut the outer BX armor using a hacksaw and a strong pair of pliers or wire snippers. A BX cutting tool is essential if you expect to carry out a lot of cutting.
The home was recently framed and paneled, but the electrical was not yet installed. For those prioritizing long-term safety and robustness, especially in commercial or industrial settings, BX cable is worth the extra investment. For instance, if you want to strip insulation from a 12-gauge wire, you should select the hole that is labeled ’12’. If you want to connect any devices, you must first strip the wire insulation from copper wire using manual wire strippers. The National Electrical Code puts the required minimum amount of cable that should extend past the junction box. However, not all these cables are available for application in all circumstances.
One major hangup I have is that it seems like it would be possible to nick the hot conductor with a screw, bolt, nail, etc. and not trip a breaker if the ground wire was not also contacted. This would or could lead to energizing whatever pierced the wire as well as possibly creating a slight arcing situation in the wall building heat and leading to a fire. With Bx the armor is the ground so if its pierced and the hot conductor is compromised a short will always occur indicating a problem. Like I said I’m looking to educate myself on the benefits/drawbacks of Romex since I have not used much at all. The main difference between BX and Romex is the outer protective covering. Otherwise, modern BX and Romex have positive, neutral, and ground wires.
Forums General Topics of the Trade General Discussion Area Romex vs. BX or MC cable
- Since the metal edges are always sharp, you should caution while cutting.
- For example, the earliest versions didn’t include a bonding wire (they used only the armor for a ground path), so its armor could get dangerously hot in a fault condition.
- If construction, remodels and renovations are done with BX, the electric field exposure is significantly reduced.
- The main difference between BX and Romex is the outer protective covering.
- This is why I always use BX on my own jobs and recommend it on any project in which I am consulting.
BX is among the earliest electrical cables designed for commercial and residential uses in the early 20th century. We also offer other types of electrical solutions including electrical panel replacement, whole-house generator configuration, ceiling fan replacement, safety inspections, and lighting installation. By partnering with our team, you can rest assured that we will thoroughly inspect the electrical wiring in your house, identify the materials used, and perform any necessary installation or replacement services. Similar to MC cables, BX wires offer various pros and cons due to their shared characteristics and usage restrictions compared to non-metallic (NM) cables like Romex.
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The NM (Non-metallic) naming refers to the out sheathing that covers individual wires being non-metallic. It is different from conduit wiring or metallic sheathed cables, which involve individual conductors being protected and surrounded by a metal conduit or metal coil. Romex wire has a non-metallic plastic protective covering that is easy to handle.
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In BX, the ground wire has a plastic protective sheathing, whereas Romex, the copper wire, is bare. For instance, a cable labeled ’14-2 with ground’ has 14-gauge wires, a copper grounding wire, and two insulated conductors. Before you settle on buying BX cables, it’s essential to understand that these wires have a corrugated surface and are heavy, thus making it hard to pull through stud holes. In addition, without severing or cutting the inner wire, it would be hard to cut the BX metal sheathing. Many homeowners prefer non-metallic (NM) electrical cables, such as the widely known Romex, because they are lightweight, easy to handle, and affordable.
The wire sheathing, in this case, won’t degrade or turn gummy over time. Additionally, MC cables do not have a limit on the number of conductors they can contain, whereas BX cables can hold up to four insulated conductors. NM cable is by far the most common type of wire used in single-family residential applications today and been used extensively for the past 40 years. Since the 1960s, Knob and Tube has not met current electrical code thus any renovations or new construction built in the last 50 years should contain more modern wiring. The fact that BX cables have a metal shield makes them that much more durable than other types of cables. Although it has some flexibility, it is not nearly as flexible as a vinyl cable, and therefore more difficult to work with.
At its core, BX cable is made up of several insulated wires and one ground wire which may or may not be insulated and held together with strips of paper wrapped around them in a spiral fashion. I want to install fiber-optic cable in the walls to future-proof our home. Fiber-optic is much faster, can handle more information, and ensures less latency than either wireless or ethernet cable. Years ago, we went “wireless-free” by hard-wiring all stationary electronics and communication devices in our home and office.
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The cable jackets are color-coded to permit identifying the cable sizes quickly—black jacket for #6 and # 8 AWG, orange jacket for # 10 AWG, yellow jacket and red jacket for # 12 AWG, and white jacket for # 14 AWG. NMD90 Red sheathing is only used for wiring baseboard or convection heaters. If you are thinking of running wiring in your home, you will have several options for the type of wire to use and how to protect it; however, two of the most common and popular choices are NM cable and armored cable. The individual conductors in the cable are metallic with about 65-percent copper.
BX can also be embedded in plaster on masonry and run in the air voids of masonry walls, under raised floors, and in air-handling spaces. And, again, take note that these allowances don’t apply if any of those spaces are prone to getting wet. WesBell Electronics, for example, basically says AC, BX, and MC are all equivalent. This matters because MC cable can be used outdoors in certain circumstances, but BX/AC never can be, contrary to many online sources.
The tool will cost you about $20 to $50 and make the task of ripping and splitting back BX cable safer and easier than using hands. It’s therefore vital that you check with the local building and electrical codes whether or not BX cables are left exposed. If old BX wires are in good condition and capable of handling today’s increased power demands, there is typically no need to replace them. The time spent diagnosing the problem, locating the short, cutting the wall, replacing the wire, patching the wall, and painting was well over $2,500. If the architect, owner, or contractor had insisted on BX instead of NM cable, this repair would likely not have been necessary.
- 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.
- The tool will cost you about $20 to $50 and make the task of ripping and splitting back BX cable safer and easier than using hands.
- BX wiring emerged in the early 20th century for residential and commercial applications.
- Both are sometimes simpler to install that wire in conduits, which reduces the cost.
The very mention of “BX” produces alarm in the eyes and heart of many romex vs bx older electricians and home inspectors, because early versions of BX were deeply flawed. Those flaws have been corrected in the modern product, which is allowed by the NEC as AC cable, while old-style BX is not. According to JP McCurdy Electrical Services, a lot of the negativity surrounding BX cable comes from both the shortcomings of the old-style cable and the misuse or misunderstanding of the cable in the first place.
You calculate its properties as a conductor by stretching it out to its uncoiled (and much greater) full length, because the interlocking edges aren’t considered a strong enough electrical link. One added benefit of NM cable over knob and tube is that knob and tube emits fairly high levels of low frequency alternating current magnetic fields, due to the separation of the hot and neutral conductors. The magnetic field strength around knob and tube carries a good distance from the wires and is proportional to the distance between the hot and neutral conductors. Inside NM cable, the hot and neutral conductors are side by side, thus NM emits a much smaller, more localized and weaker magnetic field. The magnetic field strength drops very quickly with distance from the NM cable. Cable manufacturer Southwire claims BX can reduce installation costs by 50%, as compared to conduit and wire.
The unique downsides of BX are that it cannot be used in wet, damp, or exterior locations, and obviously it cannot therefore be direct-buried or used as aerial cable. It turns out there are versions of MC that share all of the potential major pros of BX and none of the cons (via North Central Washington Home Inspections). Less EMI translates into a better function for all electronic devices, reduces the electric field size, and causes a minimal EMI coupled to the indoor E and B fields. Yesterday, I mentioned that my dream is to build our family’s home someday and install BX cable and fiber-optic light pipe into the walls.
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