Clarifying NEC Articles 725 and 800

Electrical engineers should understand the differences between NEC Article 725 and Article 800, and how to apply them in low-voltage telecom projects.

07/17/2013


Learning objectives

  • Understand NEC Articles 725 and 800, and how they affect network cabling for electrical engineers.
  • Determine which Article to start from, depending on the circuit type being installed.
  • Identify how the circuits from the two Articles support each other in installation requirements, shared pathways, and cable type substitution. 

Figure 1: This is a typical telecom horizontal cable segment. Courtesy: CH2M HILLWhy is there so much confusion among professionals in the telecom, networking, and electrical cabling industries on the application of National Electrical Code (NEC) Articles 725 and 800? The confusion is apparent when you ask the question, “What section of the electrical code is applicable to a telecom cable routed from a telecommunication room to a telecom outlet?” (see Figure 1). The segment of cable described makes up almost 100% of the cabling that is designed for a network connection to a desktop computer, workstation, and telephone. Figure 1 shows cabling connected to a network switch, which in turn is connected a file server not shown in the diagram. It also shows a cable connected to a 110 block, which is cross connected to a private branch exchange, typically known as a PBX.

I have asked this question on several occasions at conferences and seminars. From a rough survey, approximately 50% of the attendees believe this segment of cable is covered under Article 800, 40% believe it is covered under Article 725, and the other 10% don’t know. I also heard it dismissed as all being “low-voltage” cable, as if knowing the applicable code section doesn’t matter.

What is low-voltage and does it matter?

First, let’s address the 10% who believe this is a not an issue because this is only a “low-voltage” cable. Is the network or telephone cable in our example really low-voltage? Yes, it is low-voltage when compared to power and lighting circuits, but the text of the NEC does not describe networking or telephone cables as low-voltage.

Article 800 does not use the term “low-voltage” to describe circuits. In Article 725, there is only one reference to the term “low-voltage” as it relates to power limited tray cable, and that does not apply to our application. The NEC does not have a formal definition of the term in Article 100: Definitions. The term is defined in a few different articles in the description of clearances and of healthcare facilities, and in Chapter 6 for special equipment. None of these terms directly applies to a network cable.

Often the authority having jurisdiction (AHJ) over the installation of this cabling type requires some form of low-voltage or limited voltage license to be held by the contractor performing the installation work. I suspect this is where the casual use of the term “low-voltage” comes from, but it does not provide an excuse for being dismissive in understanding the correct classification for this circuit. There is a good reason why the NEC covers network cabling. Even though a network cable does not present harmful voltages, there are a variety of safety issues to be considered such as separation from power circuits, the correct classification of the cable for the environment, cable support, and routing, to name a few.

As more network cabling is installed, the more important it becomes to understand the proper classification of the circuit types. It is not hard to see in the telecommunications industry a steady pace of converging technologies. It started with data and telephone systems and has evolved to security, access control, closed-circuit TV, radio, and control systems.

If you have seen terms such as VoIP, RoIP, or SoIP (voice over Internet protocol, radio over Internet protocol, and storage over Internet protocol, respectively), then you are a witness to the convergence of other technologies with telecommunication systems. The continued convergence of systems using network cabling reinforces the need to properly understand the section of the code that applies to network cabling. As professionals in this industry, whether inspector, designer, or installer, we have an obligation to know how to properly classify the circuits in the NEC to ensure their safe design and installation.

Defining a communication circuit

Let’s consider the 50% of the folks who believe the circuit described in Figure 1 is covered under Article 800. They have a pretty good argument. The circuit described is commonly called a “communications circuit,” and aren’t the terms “telecommunications” and “communications” interchangeable? The cabling installed for a network connection in our example is an unshielded twisted-pair cable, which is very similar to the construction of cable used for legacy telephone cabling. To this day we commonly use the same cable and cabling components for both networks and telephones. The best argument supporting the application of Article 800 is that the cable installed for networking will be marked CM, CMR, or CMP per the NEC, and the NEC defines these in Article 800. If you were to take a moment to look at the network cable connected to your laptop or workstation, you would most likely see one of these cable markings.

All of these arguments would lead you to the wrong conclusion. Unfortunately, I have seen manufacturers in our industry enforce this belief by mentioning only Article 800 in their design guides and other informative literature. I suspect some of this is due to the forefathers of our network cabling technologies coming out of the telephone industry where Article 800 is rightfully applied. To see why Article 800 does not apply to the segment of cable described in Figure 1, it is important to understand the scope and definition of Article 800.

Article 800 is titled “Communication Circuits.” Within the NEC it goes on to define the scope of the article in 800.1 as: “This article covers communication circuits and equipment.” Therefore, to understand the scope of this article, it is necessary to understand the definition of a communication circuit. Depending on the text, design guide, or industry standard you look at, you will probably see something that describes our circuit in Figure 1. In this case, these other sources that define this term are irrelevant. When interpreting the code, the perspective that matters is how the NEC defines a communication circuit. The NEC in 800.2 states:

Communications Circuit: The circuit that extends voice, audio, video, data, interactive services, telegraph (except radio), outside wiring for fire alarm, and burglar alarm from the communications utility to the customer’s communications equipment up to and including terminal equipment such as a telephone, fax machine, or answering machine.

In typical NEC language, this definition is not written in a form that would make it easy to understand. Without changing the meaning of the definition, consider the same sentence in a different form.

Communications Circuit:

The circuit that extends:

  • Voice
  • Audio
  • Video
  • Data
  • Interactive services
  • Telegraph (except radio)
  • Outside wiring for fire alarm
  • Burglar alarm, from the communications utility to the customer’s communications equipment up to and including terminal equipment, such as a:
    • Telephone
    • Fax machine
    • Answering machine. 

The first eight bullets are types of circuits being extended from a communication utility. The bottom three bullets describe the type of customer terminal equipment the utility is connecting to. Therefore, what the NEC is defining as a “communication circuit” is that which extends a communication utility circuit to a customer’s terminal equipment.

This is important to understanding the scope of Article 800. Article 800 applies only to those circuits being extended by the communication utility, with “communications utility” being the key term. In our example in Figure 1, the network cable is not extending a service from the communications utility. What is shown is a privately owned network circuit, and it is being extended in the building from a customer-owned network switch to a customer owned workstation.

Therefore, what the NEC is defining as a “communication circuit” is that which extends a communication utility circuit to a customer’s terminal equipment.

Within Article 800 there is no definition of a communications utility. There is, however, an informational note under section 800.1: Scope that refers you to section 90.2(B)(4) for the installation of circuits that are not covered by Article 800. Paragraph 90.2(B)(4) says that the “installations of communications equipment under the exclusive control of communications utilities located outdoors or in building spaces used exclusively for such installations” is not covered by the NEC. The informational notes at the end of 90.2(B)(4) define a “utility” as an entity that is typically recognized by public regulation such as in the case of electrical supply generation, telephone, and cable television services. Therefore, when Article 800 is referring to a communication utility in the communication circuit definition, it is referring to a circuit from a utility company.

From this we can tell the NEC does not apply to utility company buildings or the services outside that are controlled by a utility company. There are times when the telephone utility service needs to extend services (or circuits) inside a privately owned building—for example, in the case where T1 lines, digital subscriber lines (DSL), or plain old telephone system (POTS) lines need to be extended into a building to a customer’s telephone switch or network equipment. Article 800 provides the code requirements for this cabling. In modern telecommunication networks, the cabling of this type is a fraction of the cabling covered by NEC 800, but this wasn’t always the case. Since the privatization of telephone systems and the emergence of network computing, the services of the telephone companies’ equipment and cabling in the private enterprise have been diminishing.


<< First < Previous 1 2 Next > Last >>

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
Control Engineering Leaders Under 40 identifies and gives recognition to young engineers who...
Learn more about methods used to ensure that the integration between the safety system and the process control...
Adding industrial toughness and reliability to Ethernet eGuide
Technological advances like multiple-in-multiple-out (MIMO) transmitting and receiving
Virtualization advice: 4 ways splitting servers can help manufacturing; Efficient motion controls; Fill the brain drain; Learn from the HART Plant of the Year
Two sides to process safety: Combining human and technical factors in your program; Preparing HMI graphics for migrations; Mechatronics and safety; Engineers' Choice Awards
Detecting security breaches: Forensic invenstigations depend on knowing your networks inside and out; Wireless workers; Opening robotic control; Product exclusive: Robust encoders
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
News and comments from Control Engineering process industries editor, Peter Welander.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
Anthony Baker is a fictitious aggregation of experts from Callisto Integration, providing manufacturing consulting and systems integration.
Integrator Guide

Integrator Guide

Search the online Automation Integrator Guide
 

Create New Listing

Visit the System Integrators page to view past winners of Control Engineering's System Integrator of the Year Award and learn how to enter the competition. You will also find more information on system integrators and Control System Integrators Association.

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.