Following the (Electrical) Code
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It is widely known that Wi-Fi gained its first foothold in the residential/consumer market and then began its transition to the workplace. With this transition began the rise of the enterprise-grade wireless local area network (WLAN). Enterprise grade WLAN hardware is specifically designed to operate in a commercial office environment. Besides being robust enough to handle enterprise level network requirements, the hardware is also designed to meet the extra electrical code requirements necessary in commercial office space. Simply put, the hardware and installation techniques used in a residential WLAN generally will not comply with the regulatory requirements of a commercially installed WLAN. The purpose of the electrical code is to prevent fire and smoke hazards.
Various regulatory bodies specify the safety requirements of electrical hardware and installation techniques. These bodies include, but are not limited to, the National Fire Protection Association (NFPA), the American National Standards Institute (ANSI), the Underwriters Laboratories (UL), and the Institute of Electrical and Electronics Engineers (IEEE, which also sets the standards for 802.11 WLANs).
The specifications from these regulatory bodies are usually just guidelines, and it is not their duty to enforce them. It is usually the responsibility of the state and local electrical code officials (inspectors) to enforce the parts of the electrical code they deem applicable to their local jurisdiction. Interpretations of the electrical code can vary greatly among jurisdictions. This is just an overview of the nationally recognized standards; check with your local electrical inspection department for detail on how the code is interpreted in your area.
Compliance with the various codes can be broken down into three areas: the access point (AP) hardware, communications cabling, and antenna installation. Each area has its own relevant code(s).
In most office environments, the access point will be mounted above an acoustical drop ceiling. Such a hung ceiling is a grid of tiles suspended from the roof or floor above. Often, the space between the acoustical ceiling and the next floor is used as an environmental air return or plenum space. This air return is part of the building's air handling system for heating and cooling. If smoke were to be produced in this area, it could easily spread throughout a building. Smoke produced by burning plastic can be extremely toxic and when this gas comes into contact with water, it can produce acid that will cause blindness. Without the ability to see, people in a fire situation will not be able to find the exit.
To minimize the hazard of toxic smoke production, all access points installed above an acoustical ceiling must be what are called 'plenum rated'. To check if an AP is plenum rated, see if it complies with UL standard #2043.
Besides the hardware being in compliance, the installation method should also comply with NFPA National Electrical Code (NEC) standards. The latest edition of the NEC was published in 2002 (NFPA document #70) and the next version will be out in 2005. It is updated every three years in order to follow technological advances. Check out section 300.22c 'Wiring in Ducts, Plenums, and Other Air-Handling Spaces' in the NEC 2002. For communications cabling guidelines, check out Article 645 'Information Technology Equipment' and Chapter 8 'Communications Systems'.
Plenum ratings apply to any communications equipment or cabling in the area above the acoustical ceiling. For the most part, consumer grade access points are not plenum rated. This is yet another reason why IT administrators should strictly forbid workers from introducing home access points into the office environment. Not only could your network security be compromised, but also you are opening yourself up to major liability in the event of fire.
Also, beware of the system integrator who promises an extra low hardware and installation cost for your WLAN project. They may be cutting costs by not using plenum rated access points and plenum cabling.
The cabling connected to the AP must also be plenum rated if it is above the ceiling. Plenum rated Category 5 Ethernet cabling should have a mark of CMP, which stands for 'Communications Plenum Cable'. Look at table 800.50 in the NEC for a listing of approved cables that can be installed in the plenum without the use of a conduit (metal raceway). Plenum cable costs more, but that is the price that must be paid to comply with the law and maintain safety.
There are very stringent rules for the routing of communications cabling covered in Chapter 8 of the NEC. Areas that you should pay careful attention to are the cable mounting (800.52) and abandoned cables (800.2). Because of the in-depth language of the code, one should read all of Chapter 8 to be familiar with the requirement of communications cabling.
Although it is done on a routine basis, using a zip tie to mount a Cat 5 cable is unacceptable and unlawful. There are specific guidelines for mounting and acceptable devices for mounting communication cables. Erico Caddy Fasteners for one has a great mounting guide for communications cabling that puts it in plain English.
With most office buildings, each new tenant installs their own communication cabling and leaves the old cabling in place. This creates what the NFPA calls a 'high fuel load' because of the excess cable capacity and increased fire and smoke hazard. In 2002 the NEC created new rules that require the latest installer to remove all abandoned cables from a building upon performing a new installation. For communications cabling the removal applies only to cable not enclosed in a metal raceway. This means that if there is unused Cat 5 in the plenum on a cable hanger it must be removed. To avoid this problem in the future, it may be a good idea to use metal conduit.
Antenna systems add yet another dimension to the electrical code, especially if the access point or antenna will be mounted outdoors. For the most part, you need to be concerned with the grounding of the outer conductor of antenna transmission line (coaxial cable) when the antenna is placed outdoors. Pay careful attention to the proper grounding distances, bonding, and soil conductivity.
This is to prevent and reduce the effect of surges produced by lightning strikes. Article 810 covers 'Radio and Television Equipment' while Article 820 covers 'CATV and Radio Distribution Systems' in the NEC. Also note the guidelines for conductors entering a building in Article 800 part II. With the rapid expansion of both consumer and enterprise grade wireless devices, the electrical code has some catching up to do and more detail on WLAN may be covered in the 2005 version.
The electrical code can be quite confusing when implementing a wireless LAN or Wi-Fi enabled network. Because a WLAN covers so many aspects of both wired and wireless technology, there are many areas where one could fail to comply with the electrical code. Compliance with the code is important for both safety and legal reasons. Whether you are planning to deploy a small scale or large-scale network, it is probably best that you seek professional help from a design firm to handle your compliance needs. Hopefully this tutorial has given you enough of an overview that you know what questions to ask your system integrator and what to look for in a properly installed system.