NM-B Electrical Wire vs. UF-B Electrical Cable: Are They Really Interchangeable?
If you ever shopped for an electrical cable without a specific type in mind, you know that some cables are interchangeable when it comes to particular applications. However, in some cases, the cables are compared falsely and are not that similar. NM-B electrical wire and UF-B electrical wire are an example of such false pairing. Did someone suggest that you could use one or the other for connecting indoors to outdoors? Continue reading if you wish to know whether it is the best option for you.
The Definitions of NM-B Wire and UF-B Wire
NM-B is a non-metallic electrical wire used in residential building wiring for various devices and outlets. It is mostly used in devices characterized as damp or wet, such as washing machines and dishwashers. It can also be applied in switches, tile walls, and lighting. The outer PVC jacket of the NM-B electrical cable is tough and does not need extra protection. The ground wire does not need insulating, and the strands are sheathed with paper wrappers.
UF-B stands for "underground feeder cable." UF-B electrical cable is designed to bring power from indoor to outdoor constructions. It is suitable for direct burial without an electrical conduit because of the durable rubber sheathing that protects it from damage during installation and maintenance. Each of the wires of UF-B is extra-sheathed individually.
Indoors vs. Outdoors- Critical Difference
The most crucial difference between UF and NM-B is that the latter is prohibited for outdoor use. Though UF and NM-B have many things in common, NM-B wire can quickly rot if mistakenly used outside because it does not have the extra-protection of UF-B. Despite this, NM-B wire is sometimes allowed to leave the building for a short distance. In this case, it has to be placed in an electrical conduit or another necessary type of protection. However, it is still not advised to use it outdoors unless unavoidable because weather damage is very much possible.
UF electrical wire is perfectly suitable for most NM-B applications, though it is unnecessary to use it because it is too expensive for indoor applications. When used as NM, UF-B has to comply with the standards found in NEC 2008 and NEC 2011 Article 334.
The difference in pricing between NM-B electrical wire and UF-B electrical wire happens to be drastic. Generally speaking, UF-B is about 20 percent more expensive than NM-B. Therefore, it is better to use NM-B for simple projects in the house as long as local regulations do not restrict its use.
Mind The Installation
Though we discovered that applications of NM-B and UF-B are drastically different, one thing they share is that they are not relatively easy to install. The process of installation goes beyond some basic precautions.
NM-B Wire Installation
NM-B Wire cannot be used in multifamily houses and commercial buildings that are three floors above grade. It also cannot be used as a service entrance cable in hazardous areas. The cable can be installed exposed in locations such as garages, attics, and basements, but in this case, it has to strictly follow the surface of the building and be properly fastened. It should not be installed in areas where it can be damaged or subjected to physical abuse. NM-B wire can be installed in conduit, pipe, raceways, and other types of protection. If the wire is used outdoors for a short distance, you should opt for lower ampacity.
UF-B Wire Installation
When installed underground, UF-B has to be placed 24 inches below the service so that minor movements will not damage the cable. The conduit is needed where the cable is exposed and goes into the ground outside of the house. UF-B Wire is best used for direct burial where the soil is easily diggable.
Now that you know more about the installation and applications of NM-B and UF-B, visit our website for more details.
