Section 310.2 requires that all conductors be insulated (A). The exemption, however, notes that bare conductors are acceptable where other portions of the code allow it, such as 250.119, which indicates that egc can be bare, covered, or insulated. Click to enlarge...
Thus, a cable assembly consisting only of an aluminum conductor without any insulation around it would be considered a metal-clad cable under 310.2(A). This means that it must comply with the requirements of this section regardless of whether it is also covered by another material, such as rubber or plastic. A cable assembly that contains both insulated and non-insulated conductors would require both types of conductors to be marked with their respective codes to determine what the overall rating of the cable is.
The term "metal-clad" was not defined by the original version of the code but was added later by ANSI as a definition for its purposes. Both the American Wire Gauge Association (AWGA) and the International Electrotechnical Commission (IEC) include metal-clad cables in their definitions of "aluminum cable". However, neither organization has defined "metal-clad" nor does the term appear in the code text itself. Thus, it is recommended that you refer to the specific requirements set out in individual sections when determining which type of cable is required.
Senior staff member Re: Is There Any Bare Ground in the Conduit? This would include conduit wiring.
If you look at the picture below you can see the black conductor is not insulated. It goes from house to house via an underground conduit system. This is allowed under 310.2 because there are other parts of the code that allow it - in this case 250.119.
As long as other portions of the code allow it, a ground conductor can be bare in a conduit installation. It's important to remember that without insulation, these wires can cause serious injury if they get hooked up to equipment that generates electricity, such as a power tool. Without proper protection, anyone could be hurt by touching these wires.
The best way to protect yourself and others from electrical hazards is through education. Make sure everyone who works on your project knows how to identify and treat live and dead electrical work. If you're not sure about any part of the process, ask questions until you understand everything that needs to be done.
Electrical safety is one of the most important factors when working on any project. If you aren't sure about any aspect of electrical work, don't do it yourself.
Installations with one hot conductor and one return conductor, such as those found in a 120-volt single phase, two-wire system, do not match the requirements. Sections 250.20 (B) and 250.26 (1) continue to require the grounding-electrode connection, while section 200.6 continues to require the conductor to be white or gray "neutral."
In installations like these, if a fault occurs on the white conductor, it will not be detected by a voltage meter installed on the neutral conductor. But the Code does allow for other types of voltage meters to be used on neutrals. For example, a thermal-type voltage meter can be used on the neutral conductor to detect heat from any source that would indicate a problem with the wiring system.
Electric utilities often use aluminum wire for their power distribution networks because it is more flexible than copper wire of equal size. However, aluminum has a tendency to become a hot surface through which current will find its way into anything it comes in contact with, including other aluminum wires. This can cause damage to other parts of the network or even start fires if enough aluminum wires come in contact with each other or something else that will conduct electricity.
To prevent this from happening, all metal parts of electrical systems should be connected together with steel cable or metal straps. These are called ground bonds and they provide a direct path to ground for electrical energy. Grounding cables may include copper or aluminum wire depending on what type of system they are connecting together.