When planning an electrical installation, one of the first things you’ll encounter is the type of cable to use. Among the most common choices are BX and NM cables. Both are used for residential and commercial electrical wiring projects. However, each has its own benefits based on the installation needs.
BX cable is also known as metallic sheathed cable (MC cable), armored cable, or Type AC. It was a popular choice for homes and buildings.
NM (non-metallic) cable is now more popular in modern installations. However, BX cable is still useful because it is durable and has special grounding features.
In this article, we’ll break down what BX cable is, its history, how to use it, and where it stands compared to NM cable.
Key Takeaways
- BX wiring is a type of armored electrical cable with a metal sheath.
- It offers superior puncture resistance and grounding through the metal armor.
- BX cable is heavier and more expensive than NM cable, requiring special tools to work with.
- It’s more suitable for exposed installations compared to NM cable.
- While BX cable has many advantages, it requires careful handling to avoid damaging its internal wires.
What Is BX Cable?
BX cable is a type of electrical cable that consists of plastic-coated insulated wires encased in a metal sheath. The metal covering serves multiple purposes, including providing extra durability and grounding for the wire.
This metal armor is one of the defining features of BX wiring and sets it apart from NM cables, which are typically covered in vinyl. The metal sheath of BX cable offers protection against physical damage, such as punctures, making it suitable for installations in areas with high risk of damage from nails, screws, or other objects.
Unlike NM cables, which rely on separate grounding wires, BX cable grounds through the metal casing itself. This means it can be a more straightforward option in certain situations, especially in buildings where metal boxes are used.
However, the extra protection comes at a cost, as BX wiring tend to be heavier, more expensive, and harder to work with than their non-metallic counterparts.
BX Cable History
BX cable started in the early 1900s. Its origins are linked to a time of fast urban growth and industrial development. First introduced around 1910, it became a popular choice for both residential and commercial buildings, especially as cities grew and electrical systems evolved. The term “BX” is often thought to be a reference to the Bronx, New York, where the cable gained early traction.
At the time, BX cable was a significant improvement over the older cloth-sheathed wiring that had been widely used. The new armored design offered better protection against physical damage, and the metal sheath helped ground the electrical system, making it safer. Over time, it became the standard in buildings that needed a more durable, reliable option, especially in environments with high electrical demands.
Where to Use BX Cable
BX cable’s most notable advantage is its metal sheath, which not only provides physical protection but also allows it to ground through the armor itself. This makes BX a solid choice for installations where grounding via the armor is preferred or where the wiring is exposed.
For example, BX cable can be used in certain outdoor and indoor applications, such as exposed installations in warehouses or under floors, where NM cable might not meet code requirements.
It’s important to note that the suitability of BX for exposed installations can depend on local building & electrical codes, so it’s always a good idea to consult with a professional or check local regulations before beginning an installation.
In some cases, BX may not be the ideal choice for exposed areas, but its metal casing does provide a higher level of protection when compared to non-metallic cables.
BX Cable Durability
One of the biggest advantages of BX cable over NM cable is its durability. The metal sheath offers far better puncture resistance than the vinyl coating on NM cables. While NM cables can be punctured by sharp objects, such as nails or screws, BX’s armor can withstand a lot more damage.
However, this doesn’t mean BX is invincible. If the armor is compromised by sharp objects, it can still expose the inner wires to potential damage.
That being said, BX cables tend to have a longer lifespan compared to older wiring systems, such as knob-and-tube wiring, which is made of cloth and rubber insulation.
BX wiring, with its metal sheath, is far more durable and less prone to damage over time. It’s a reliable choice for electrical projects that require both physical protection and grounding.
BX Cable vs. NM Electrical Cable
When deciding between BX and NM cable, there are a few key differences to consider:
- Weight and Handling: BX is heavier and bulkier than NM cable, which makes it harder to work with. This extra weight can slow down installation time, especially in large projects.
- Cost: BX cables are more expensive than NM cables. The cost difference can add up in large projects, making NM cable the more budget-friendly option.
- Sheathing: BX cable features a ribbed metal sheath, while NM cable is coated with a vinyl sheath. The metal armor of BX offers superior protection from physical damage.
- Grounding: BX cable grounds through the metal sheath, while NM requires a separate ground wire.
- Cutting and Installation: Cutting BX cable requires specialized tools, such as BX cutters or a hacksaw, which adds to the complexity of installation. NM cable, on the other hand, is easier to cut and strip using basic tools.
How to Rip/Cut BX Cable
Cutting BX cable requires a bit more effort than working with NM cable, but with the right tools, it’s manageable. The most common method of cutting BX cable is using a BX cutting tool, like a Roto-Split. This tool makes the process safe, easy, and precise. For those without specialized tools, a hacksaw can also be used, but it comes with a risk of nicking the inner wires, which can compromise the integrity of the cable.
If you’re removing the metal sheath along the length of the cable, you’ll need tools like snippers or pliers to carefully strip away the armor. Doing this carefully ensures that the inner conductors are not damaged.
Pros and Cons of BX Cable
Pros:
- Available in spools, which can speed up installation.
- Suitable for some exposed installations, where NM cable might not be approved.
- Enhanced puncture resistance thanks to its armored design.
- Offers grounding through the metal armor, reducing the need for a separate ground wire.
- Better physical protection from damage by nails or screws.
Cons:
- Less flexible than NM cables, making it harder to work with in tight spaces.
- Requires specialized tools for cutting and stripping, increasing installation time.
- Heavier and bulkier, which may slow down the installation process.
- Typically more expensive than NM cable, making it less ideal for budget-conscious projects.
Need a Commercial Electrician?
If you need help with BX cable installation or other electrical services, Right Touch Electrical can help. With years of experience and a commitment to safety and quality, we provide electrical services that meet all industry standards. Whether you’re working on a small residential project or a large commercial installation, Right Touch Electrical is ready to assist and provide quality with a master’s touch.
FAQs
What is the difference between BX and NM cables?
BX cables have a metal sheath that provides durability and grounding through the armor, while NM cables are made of vinyl and require a separate ground wire.
Can BX wiring be used outdoors?
BX cable can be used in some exposed installations, but you should check local codes to ensure it’s approved for outdoor use in your area.
Is BX cable more expensive than NM cable?
Yes, BX cable is generally more expensive than NM cable, largely due to its metal sheathing and durability.
How do you cut BX wiring?
BX wiring requires specialized tools, such as BX cutters or a hacksaw. Always be careful when cutting to avoid damaging the inner wires.
Is BX cable more durable than NM cable?
Yes, BX’s metal sheath offers superior puncture resistance, making it more durable than NM cable, which has a vinyl covering.
Final Thoughts
BX cable remains a valuable option for electrical installations, particularly in areas where protection from physical damage and grounding through armor are important. While it may be heavier and more expensive than NM cable, its durability and ability to be used in exposed locations make it a solid choice for certain projects.
As always, when deciding between BX and NM cables, it’s essential to consider your specific needs and consult local codes. For professional installation or advice, don’t hesitate to reach out to experts like Right Touch Electrical.