Speak the Same Language and Avoid Trouble
Don't get hung up on the intricacies of Art. 800
It's probably safe to say that office workers don't spend much time thinking about the wiring that makes their phones work. As long as the cord between the base and the jack in the wall is connected, they're happy. But as anyone who's ever reviewed the requirements of Art. 800 Communications Circuits and installed a communications system can attest, it's not quite that simple.
The point of demarcation between the telephone company and premise phone wiring is the primary protector unit (Fig. 1 at right). Everything on the facility side of that point is the responsibility of the installer and is bound by the requirements of Art. 800. Of course, the word “communications” no longer just applies to the telephone, so that article also applies to wiring for other communications purposes, including local area networks (LANs) and alarm systems connected to central stations.
Of the eight definitions in 800.2, “point of entrance” may be the most important — it applies to cable grounding (800.33) and determining the length of unlisted cable inside a building (800.50, Exception No. 3). This is where the cable emerges from an external wall or a concrete floor slab, or from a rigid metal conduit or intermediate metal conduit grounded to an electrode, per 800.40(B).
Mechanical execution. Route cable so suspended-ceiling panels don't interfere with access to electrical equipment. Secure cables to structural components by straps, staples, hangers, or similar fittings designed and installed so as not to damage the cable (Fig. 2).
Attach cables exposed on the surface of ceilings and sidewalls to the structural components of the building in such a manner that normal building use won't damage them. If you install cables near framing members, protect them against physical damage from penetration by screws or nails by 1.25 in. separation from the face of the framing member, or by a suitable metal plate, per 300.4(D).
If you install cables in hazardous (classified) locations, do so per Chapter 5 requirements. Where practicable, leave a separation of at least 6 ft between communications wires and cables on buildings and lightning conductors.
Provide listed protective devices if your installation meets any of the conditions listed in 800.30(A). For example, if lightning is common in your area, be sure to install protective devices, per 110.3. You can use fuseless primary protectors under the conditions listed in 800.30(A)(1). Otherwise, you must provide fused primary protectors.
Locate fused primary protectors in, on, or immediately adjacent to the building being served and as close as you can to the point of entrance. Don't locate them in hazardous areas, except as permitted by 501.14, 502.14, and 503.12.
Ground the metallic sheath of telephone cable and primary protectors as close as practicable to the point of entrance of the phone cable to the building (800.33). Review 800.40 to determine the preferred grounding method. Keep in mind the following points concerning grounding conductors:
They must be insulated and listed as suitable for the purpose.
They must be copper or other corrosion-resistant conductive material, stranded or solid.
They can't be smaller than 14 AWG.
The primary protector-grounding conductor must be as short as practicable. In one- and two-family dwellings, the primary protector-grounding conductor must not be longer than 20 ft. The 20-ft rule isn't always possible to comply with. So you can ground the primary protector to a separate 5-ft communications ground rod (800.40). You must bond the ground rod to the power grounding electrode system with a conductor not smaller than 6 AWG.
Run them to the grounding electrode in as straight a line as practicable.
Where necessary, guard them from physical damage. Where the grounding conductor runs in a metal raceway, bond each end of the raceway to the grounding conductor or the same terminal or electrode as the grounding conductor.
Utilities were using 5-ft ground rods before the NEC began to cover communications systems. However, nothing prohibits you from using a longer rod. You must connect the grounding conductor from that rod to the nearest of the locations listed in 800.40(B). If the building or structure has a grounding means, Fig. 3 at right applies. The last FPN in 800.40 brings out an important concept: bond together all separate electrodes to limit potential differences between them and between their associated wiring systems.
Raceways are optional for communications circuits (800.48). You can install communications cables in any of the Chapter 3 raceways, if you do so per the appropriate Article for a given raceway. However, conduit fill restrictions don't apply to communications cables or conductors installed in a raceway.
You can also install communications cable in listed communications raceways, per 800.51(J), (K), or (L). Communications raceways are similar in nature to electrical nonmetallic tubing (ENT). Apply 362.24 through 362.56.
The recommendations of the BICSI Cabling Installation Manual include specific pulling tension on the cables. The generally accepted practice is to size the raceway so the cables don't exceed the percentage fill listed in Chapter 9, Table 1.
Listing and markings.
Use only communications cables listed as suitable for the purpose and marked in accordance with Table 800.50 — and install them per 800.52. However, there are exceptions. For example, listing and marking aren't required where the cable enters the building from the outside and runs in rigid metal conduit or intermediate metal conduit, and when the raceway is grounded to an electrode, per 800.40(B). If installing in plenums, risers, or other environmental air spaces, review 800.51 carefully.
Don't mark the 300V ratings on these cables — misinterpretation can suggest the cables may be suitable for Class 1, or electric light and power applications. For specific applications of cable types and what listing is appropriate, see 800.53.
Never attach communications cable to, or support it with, raceway (300.1) or the power service mast (230.28). Support via “cable tie to conduit” isn't an acceptable method.
Communications cables can be in the same raceway or enclosure with cables of any of the following (800.52):
Class 2 and Class 3, Art. 725.
Power-limited fire alarm systems, Art. 760.
Nonconductive and conductive optical fiber cables, Art. 770.
Community antenna television and radio distribution systems, Art. 820.
Low-power, network-powered broadband communications circuits, Art. 830.
Communications cables can't be bundled in the same sheath with Class 1 circuits. Class 2 and Class 3 circuit conductors can be in a sheath with communications circuits, if the Class 2 and Class 3 circuits are contained in listed communications cable or multipurpose cable.
Communications conductors can't run in any raceway, compartment, outlet box, junction box, or similar fitting with conductors of electric light, power, or Class 1 circuits, but there are exceptions.
Separate the conductors from the power or Class 1 conductors by a barrier.
Introduce power circuit conductors only to connect to the communications equipment. The power circuit conductors require at least 0.25 in. of separation from communications circuit conductors.
In other applications, you must separate communications conductors by at least 2 in. from any electric light, power, or Class 1 circuit conductors, unless you install those conductors per a Chapter 3 wiring method, such as raceway, metallic or nonmetallic sheath, or UF cable.
When you install communications wiring and equipment in hollow spaces, vertical shafts, ventilation, or air-handling ducts, do so in a way that doesn't substantially increase the possible spread of fire or products of combustion. Use approved firestops for openings made in fire-rated walls, floors, and ceilings. If there's any abandoned cable, remove the accessible portions to limit the spread of fire or products of combustion within a building. This rule doesn't require the removal of concealed cables.
Art. 800 can be dizzying if you try to memorize all of its listing requirements and other details. These things, important as they are, primarily support two concepts. One of those is that you must maintain firestop integrity. The other is you must maintain separation from higher energy levels that require more stringent wiring methods and protection. If you keep these concepts in mind as you work with Art. 800, you'll be able to ring up one job after another with no callbacks for Code violations.