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If you're installing or maintaining technology wiring systems, you'd better understand the Code rules that govern their installation, as well as the individuals involved in their enforcement.
We all know the National Electrical Code (NEC) was developed to protect persons and property from the risks associated with the use of electricity - and that its rules cover all kinds of installations. What you might not know is that the Code also applies to audio, video, Cat 5, control, data, signal and telephone systems - with the exception of railway signaling and communications wiring, and communications equipment and wiring under the exclusive control of a communications utility.
Where can you find the Code rules that apply to technology wiring? Let's start by reviewing the NEC, the arrangement of its content, and the means by which local jurisdictions enforce it.
The Code consists of an introduction and nine chapters, divided as follows:
General rules. The Introduction and Chapters 1 through 4 apply to all electrical installations, including low-voltage or limited-energy wiring (i.e., what I refer to as technology wiring) discussed in Chapters 6 and 7.
Special rules. Chapters 5 through 7 apply to special occupancies, equipment, or conditions. It is important to note that the requirements noted in Chapters 5, 6, or 7 could modify the requirements noted in Chapters 1 through 4.
For example, Sec. 300-3(c)(1) permits conductors of circuits rated 600V nominal (or less), AC circuits, and DC circuits to occupy the same equipment wiring enclosure or raceway, if all conductors have an insulation rating equal to the maximum circuit voltage applied to any conductor. However, Sec. 725-3 states that Sec. 300-3(c)(1) does not apply to Class 2 and 3 wiring. Therefore, the NEC does not permit Class 2 and 3 wiring with power conductors because of the requirements set forth in Sec. 725-54(a)(1).
Communications systems. Chapter 8 contains the requirements for communication circuits, such as telephones, satellite dishes, TV antennas, Cat. 5, and broadband systems. The requirements within Chapter 8 are independent of the requirements contained in Chapters 1 through 7 - unless a specific reference in Chapter 8 is made to a requirement in those earlier chapters.
Tables. Chapter 9 consists of tables used for sizing raceway, calculating conductor fill, and determining limited-energy systems.
Code enforcement. Although the NEC is purely advisory, it is intended to be adopted by governmental bodies and other inspection departments. However, it is up to these bodies (states, counties, cities, etc.) to adopt the NEC as a legal requirement for electrical installations.
The enforcement of the NEC falls under the authority having jurisdiction (AHJ). Generally, the AHJ is an electrical inspector employed by a government agency. He or she is responsible to an advisory council or board for decisions or rulings, including:
Interpretation of rules. The AHJ is responsible for interpreting the rules found in the NEC. This means the inspector must base his or her interpretation on a specific rule. If an inspector rejects an installation, you have the right to know the specific NEC rule you violated. The AHJ does not have the authority to require an installation to exceed the requirements of the NEC.
Approval of equipment and materials. The Code requires some equipment to be listed for its use. The AHJ determines the suitability of equipment and approves its use. The basis of equipment approval is often the listing by National Recognized Testing Laboratories (NRTL) (see Secs. 90-7 and 110-2).
Here's an example. The NEC requires low-voltage and limited-energy cables installed indoors to be listed (see Secs. 725-71, 770-50, 800-49, 820-49, 830-54, and 830-55). As a result, there are no low-voltage or limited-energy cables listed for installations underground, outdoors, or in wet locations. Therefore, inspectors permit you to install non-listed cables (identified by the manufacturer as suitable for direct burial and/or wet locations) in these locations.
Waiver of rules. When an installation does not comply with the NEC, the inspector may waive the requirement or permit alternate methods. The Code permits this only in situations where you are sure you can achieve equivalent electrical safety.
Waiver of new Code requirements. If the Code requires materials, products, or construction methods that are not yet available, the inspector may allow you to substitute materials, products, and construction methods that were acceptable in the previous Code.
Equipment installation. It is the inspector's responsibility to ensure you install the electrical equipment according to the equipment listing or labeling instructions. The inspector is also responsible for detecting any field modification of equipment that might void the listing and make the installation unsafe.
NRTL performs safety evaluations of products and publishes a list of equipment that meets nationally recognized test standards. Product listing and labeling decreases the need for inspectors to re-inspect or evaluate the electrical equipment at the time of installation. Listing and labeling by NRTL is the primary basis for equipment approval by electrical inspectors (see Secs. 90-4 and 110-2).
The AHJ doesn't need to inspect listed factory-installed internal wiring or the construction of the equipment at the time of installation - except to detect alterations or damage (Sec. 90-7).