in.) in diameter even if concealed, or (4) in multifamily dwellings if limited to 10-mm (-in.) diameter and nonconcealed spaces.800.1. Scope. The sections of this chapter apply basically to those systems which are connected to a central station and operate as parts of a central-station system.
The paragraph titled “Code Arrangement” of the “Introduction to the Code” (90.3) states that Chap. 8, which includes Art. 800, “Communication Circuits,” is independent of the preceding chapters except as they are specifically referred to.
800.2. Definitions. A communications circuit 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 or facsimile machine.
The connection to the facilities of a serving utility is an essential component of this definition. Ethernet connections between computers or between computers and a router are not communications circuits and are covered as signaling circuits in Art. 725.
Exposed (to Accidental Contact) applies to a communications cable that is in such a position that it would be likely to become energized in the event that a support or insulation or both failed.
Point of Entrance is the point within a building at which cable emerges from an external wall, or a floor slab, or from RMC or IMC connected to a grounding electrode by a grounding conductor as covered in 800.100(B). In such cases the use of heavy-wall steel conduit artificially extends the point of entrance into a building, doing for this wiring what 230.6 does for service entrance conductors. This is an important concept, and it holds for all of Chap. 8.
800.18. Installation of Equipment. With the exception of test equipment used temporarily, all equipment electrically connected to a telecommunications network must be listed as suitable for that purpose.
800.21. Access to Electrical Equipment Behind Panels Designed to Allow Access. It is contrary to the NEC to drape endless quantities of these cables across suspended ceiling panels in a way that limits the intended access to the ceiling cavity above them.
800.24. Mechanical Execution of Work. In addition to the usual neat and workmanlike manner requirement, this section also requires exposed cabling (which includes the area above a suspended ceiling) to be supported to structure such that normal building operations will not damage the cable. In addition, if the wiring is run parallel to framing, it must meet the 32-mm (1¼-in.) spacing requirement from the leading edge of the framing. Finally, the wiring must stay off the tie wires designed to support a suspended ceiling, in accordance with 300.11.
800.25. Abandoned Cables. This has the effect of requiring that any “abandoned” conductors—as defined in 800.2 as not being terminated or identified for future use with a tag—must be removed. It is no longer permissible to leave abandoned communications cables in place when they are no longer in use, unless they have been “identified” for future use.
800.26. Spread of Fire or Products of Combustion. This is a restatement of 300.21, as applied to this article.
800.44. Overhead Communications Wires and Cables. This section divides the topic into pole wiring and over rooftops. Part (A) covers pole work and requires communications wires to run below power wiring on the same pole if practicable, and never attached to the same cross arm. The climbing space is to be as required in 225.14(D), and there must be a minimum of a 300-mm (12-in.) separation from power wiring at any point in a span, including at their point of attachment at the load end. This reduced spacing only applies if the spacing at the pole meets the required 1-m (40-in.) spacing on the pole. Part (B) covers rooftops, and the default clearance is 2.5 m (8 ft), with exceptions for auxiliary buildings such as garages, and also for mast applications and steep roof applications that exactly duplicate the comparable exceptions for service drops operating at not over 300 V.
800.47. Underground Circuits Entering Buildings. Where in manholes with power circuits, barriers must be arranged to create a separate section for the communications circuits.
800.48. Unlisted Cables and Raceways Entering Buildings. Unlisted outside plant cables may enter a building and move through general purpose spaces (not risers or plenums) up to 15 m (50 ft) from the point of entrance. This allows a transition length along which a convenient point can be provided for a transition to the listed cables required for most interior work. If such a point is unavailable, the point of entrance can be artificially extended through the use of grounded heavy-wall steel conduit.
800.50. Circuits Requiring Primary Protectors. The requirement that creates the need for this section is 800.90, discussed below. Part (A) covers the drop wire from the last outdoor support to the protector and it must be listed for this purpose, as covered in 800.173. Part (B) covers the required 100-mm (4-in.) system separation from open power wiring (not in raceways or cable assemblies) on the outside of buildings. Note that communications wiring outdoors that is exposed (see definition above) to contact with power wiring over 300 V to ground, as on most utility poles, must be separated from building woodwork by wiring on porcelain knobs, etc., unless fuseless protectors are used or where the exposed wiring has a grounded metallic sheath.
Part (C) covers circuits entering a building ahead of the primary protector. The building must be protected from the unprotected wiring through a bushing or metal raceway, unless the entry is through masonry, or uses metal sheathed cable, or qualifies for a fuseless primary protector (see 800.173 for a cable assembly that inherently meets this requirement) or is listed drop cable extending from circuits running with a metallic sheath. Raceways must slope up in the out-to-in direction or else drip loops must be provided outside. Raceways must also have a service head, and if ahead of the protector, must be grounded.
800.90. Protective Devices. Part (A) covers where primary protectors are required, which can be summarized with respect to the entering circuits as wherever there is a lightning exposure or exposure to contact by power wiring over 300 V to ground. The second note provides good information as to where a lightning exposure might be disregarded, such as in high-rise construction areas where lightning will be intercepted, or for short interbuilding cable runs not over 42 m (140 ft) apart and running as direct burial or in underground conduit with either a metallic cable shield or the conduit being metallic. Areas on the west coast and in other locations with five or fewer thunderstorm days a year are also candidates to avoid this requirement. (A)(1) gives five instances where a fuseless protector is permitted; (A)(2) covers the fused protectors that are required in the event that local conditions do not permit qualification under one of those five allowances.
Part (B) covers the location of primary protectors, which is in, on, or immediately adjacent to the building served, as near as practicable to the point of entrance. And note the definition of that term; it is possible to extend that point through the use of grounded heavy-wall conduit. The second paragraph covers mobile homes, and accepts a protector at the remote disconnecting means as long as the distance is within NEC requirements in 550.32(A).
800.93. Grounding or Interruption of Metallic Sheath Members of Communications Cables. This rule is split into a termination outside or inside a building, but the action to be taken is the same in either event: Make a grounding connection as covered in 800.100, or place an insulating joint as near as practicable to the point of entry. Here again that point of entry can be extended through the use of conduit.
800.100. Cable and Primary Protector Grounding. Both the protector and any metallic members of a cable sheath must be grounded in accordance with the rules of this section.
Part (A) requires the grounding conductor to be listed and insulated, made of copper (or other corrosion resistant material), and stranded or solid. The size must be no smaller than 14 AWG. It must run in as straight a line as practical, and be guarded from physical damage. If run in a metal raceway, both ends must be bonded even though 250.64(E) only imposes that requirement on ferrous raceways. It must be as short as practicable, and not over 6 m (20 ft) in one-and two-family dwellings. If the 6-m (20-ft) limitation can’t be met, place an additional electrode as covered in 800.100 and then bond this electrode to the power system electrode with a 6 AWG or larger copper wire.
Part (B) covers electrode terminations. If there is an intersystem bonding termination, then the termination is to that point. If the intersystem bonding point is lacking but there is one or more grounding electrodes, the connection must be made to that grounding system through one of the optional methods listed. If the premises served have no intersystem bonding termination and no grounding electrode system, then the bonding connection is to the nearest traditional building electrode (water pipe, building steel, concrete-encased electrode, ground ring), and if all those are missing then to a 1.5-m (5-ft) ground rod, driven into permanently damp soil to the extent practicable, using connections that comply with 250.70.
Part (D) requires that this electrode, although required to be at least 1.8 m (6 ft) distant from other electrodes, must be bonded to the power system grounding electrode system with a conductor no smaller than 6 AWG copper. The power system bonding requirement is presumably waived at mobile homes for which the connection would be impractical. This is the apparent result of the wording of an exception that, in violation of the Style Manual, is not in the form of a complete sentence and therefore unclear as to effect. Refer to the discussion at 800.106 for more information.
800.106. Grounding of Entrance Cables at Mobile Homes. This is very difficult to follow, because there is no straightforward explanation of what happens when the mobile home has an electrical supply that complies with the NEC. Specifically, mobile homes are supposed to have a bonding terminal on their chassis at an accessible location, as required in 550.16(C)(1). They are also supposed to have either service equipment or a feeder disconnect located within 9.0 m (30 ft), per 550.32(A). If they have actual service equipment at that location, or if they have a feeder disconnect with a regrounded neutral at that point, there will be a grounding electrode system connected at that disconnect. In fact, even if the disconnect does not include a regrounded neutral, 250.32(A) still requires a grounding electrode connection at this point. Assuming the communications entry comes from this location, a bonding connection between the conductive elements in the communications cable jacket and the grounding system at the disconnect will meet all requirements and no further action needs to be taken at the mobile home. If, and only if, the disconnect is located at an excessive distance or grounded incorrectly does the necessity of creating a local electrode at the mobile home kick in. The context for this rule is at 800.90(B), second paragraph.
This brings up the separate question of bonding. If the mobile home is permanently connected to a code compliant disconnect, then the permanent equipment grounding system connecting the mobile home and the disconnect is sufficient for these purposes. However, if the mobile home is cord- and plug-connected, removing the plug would disrupt this continuity. Article 800 systems have primary protectors that will not exist on most other systems. That leaves only one option, a grounding electrode, and therefore, through this back door, a local grounding electrode becomes required in the event of a cord- and plug-connection. The grounding electrode must be connected to the conductive elements of the communications cable, and also to the mobile home bonding terminal as previously mentioned.
800.110. Raceways for Communications Wires and Cables. Raceways can be Chap. 3 methods or communications raceways as covered later. These raceways are very close to ENT in construction and this section even mandates the use of the installation provisions in Art. 362 having to do with bends, supports, joints, and perhaps most intriguingly, 362.56 which invokes the box-at-termination rules in 300.15. However, no raceway fill limitations apply.
800.133. Installation of Communications Wires, Cables, and Equipment. Part (A) sets forth the system separation rules, which are comparable to Art. 725 provisions. Part (A)(1) covers raceways, cable trays, boxes, and cable assemblies, in three headings, the first being uses with other power-limited circuits in raceways. The context for these rules is that communications circuits have a voltage exposure that is comparable to power-limited fire alarm or Class 3 signaling circuits. Therefore, the following systems can share an enclosure with communications cables: (1) Class 2 and Class 3 cabling—Art. 725; (2) Power-limited fire alarm wiring—Art. 760; (3) Optical fiber cabling both conductive and nonconductive—Art. 770; (4) CATV systems—Art. 820; and (5) Low-power network-powered broadband communications—Art. 830.
The second heading addresses communications circuits sharing a cable assembly with Class 2 and Class 3 circuits. In such cases the combination is allowed but the entire assembly becomes reclassified as a communications cable; and the Class 2 or Class 3 circuit is now an Art. 800 circuit and must meet the listing requirements of this article. On the other hand, there are composite cables comprised of jacketed signaling cables alongside of jacketed communications cables, all within a common overall jacket, and in this case the signaling circuit is permitted, but not required, to be reclassified as a communications circuit. Note that even though this rule does not expressly cover the topic, Type NMS cable relies on this concept, and UL has listed this sort of hybrid cable for many years, as expressly covered in 334.116(C). Such cable assemblies do not depend on conductor insulation alone to establish the required system separation, squarely in accordance with the spirit of these rules; however, the literal text of this wording is in direct conflict with the Chap. 3 permission.
The third heading addresses sharing space with non-power-limited circuits, for which the rule is no common locations allowed, but there are three exceptions. The first recognizes a permanent barrier or listed divider. The second exception allows a common enclosure where the power-limited and non-power-limited wiring must terminate on the same equipment, as in the case of some powered equipment with a communications interface. In this case there is a general solution and a limited alternative. The general solution is to restrain the wiring with duct, tie-downs, or other methods such that a 6-mm (¼-in.) air separation is maintained between systems. Note that this provision is for dead-end wiring only, not daisy chains (“solely for power supply to” does not mean to connect and then to feed another piece of equipment). The third exception correlates with 620.36 with respect to the traveling cable.
Part (A)(2) requires a 50-mm (2-in.) separation from open power wiring and other open, non-power-limited circuit conductors. Two exceptions apply, the first where a raceway on either system provides separation, or where the non-power limited wiring uses Chap. 3 cabled wiring methods. The second applies where fixed barriers such as porcelain tubes or flexible tubing are installed.
Part (B) covers conductor support and states that cables must not be tie-wrapped to or otherwise supported by electrical raceways, as also disallowed in 300.11(B). However, there is an exception for communications cables to run up a mast on its outside if it is “intended for the attachment and support of such cables.” This can never include a service mast, for which 230.28 absolutely disallows any connections thereto except the service drop conductors. Part (C) brings in the prohibition against ductwork locations subject to loose stock and vapor removal in 300.22(A). This may seem odd and commonsensical, unworthy of mention here, but Chap. 8 articles carry no baggage from the first seven chapters, except only that which they go back to get. So, this is necessary.
800.154. Applications of Listed Communications Wires and Cables and Communications Raceways. Part (A) covers plenum cavity applications, and requires Type CMP cabling. Included here are listed plenum signaling raceways, provided only the plenum grade cabling is pulled in to them. Listed wires and cabling that comply with 300.22(C) are also permitted on the reasonable supposition that power wiring acceptable by right in these areas can also be used for power-limited applications.
Part (B) covers riser applications, defined as penetrating runs of more than one floor (floor to floor can be a lesser grade). This requires Type CMR cabling at a minimum. Listed riser signaling raceways containing only CMR cabling are also permitted. In accordance with the general hierarchy discussion in Chap. 7 at 725.154, plenum cavity methods in (A) can also be used. Other listed wiring from lower levels in the hierarchy, or Chap. 3 wiring, is permitted if installed in metal raceways, or in a fireproof chase with firestops at every floor. Lower levels in the hierarchy are also permitted, including those with the “X” suffix, in one- and two-family dwellings.
Part (C) covers general (“other”) wiring in buildings not covered in (A), (B), (D), and (G). The basic method is the cabling without a suffix, as in Type CM (or CMG). The lesser residential grade CMX is permitted where (1) in raceways or other Chap. 3 wiring, or (2) in nonconcealed spaces not over 3 m (10 ft), or (3) in one- or two-family dwellings if not over 6 mm (¼ in.) in diameter even if concealed, or (4) in multifamily dwellings if limited to 6-mm (¼-in.) diameter and nonconcealed spaces. Type CMUC undercarpet communications cabling is permitted for these circuits beneath carpets.
Part (D) covers cable tray applications. Type CMP, CMR, CMG, and CM are available for this use. General purpose signaling raceways, likewise with the higher grades available for substitution, are also permitted in cable trays.
Part (E) presents graphically the cable hierarchy.
Part (F) correlates with 800.179(I) on hybrid power and communications cabling.
Part (G) requires CMP, CMR, CMG, and CM and also listed communications wire to be used in distribution frames and in cross-connect arrays. Because this wiring substitutes for CL2 and CL3 per 725.154(G), there is no conflict with 725.154(F).
800.156. Dwelling Unit Communications Outlet. In new construction, at least one communications outlet must be provided within all dwelling units and cabled to the service demarcation point of the communications utility. This is true regardless of plans to rely on cellular phone service.
800.170. Equipment. Reiterating 800.18, all communications equipment, even a lowly RJ-11 jack that will be field installed, must be listed as suitable for connection to a telecommunications network.
800.173. Drop Wire and Cable. Communications wires without a metallic shield that run from the last outdoor support to the primary protector must be listed as being suitable for the purpose, and shall have the current carrying capacity as covered in 800.90(A)(1)(b) or (c). The last condition means that they will “safely fuse on all currents greater than the current carrying capacity of the primary protector” and thereby qualify the installation as not requiring a fused protector.
800.179. Communications Wires and Cables. This section covers the listing requirements for the cables used in the applications just covered, as follows:
Part (A) covers Types CMP for plenum cavity applications.
Part (B) covers Type CMR for riser applications.
Part (C) covers Type CMG for general purpose applications.
Part (D) covers Type CM for general purpose applications. The presence or absence of a “G” suffix depends on the test protocol used. A “no suffix” cable may not have been tested to a certain Canadian standard and could be restricted in certain applications within the Canadian market.
Part (E) covers Type CMX for limited use in residential applications.
Part (F) covers Type CMUC undercarpet wires and cables.
Part (G) covers communications circuit integrity (CI) cables. These are additionally marked with the designation “CI.”
Part (H) covers communications wires, as opposed to cables, as used in cross-connect arrays and distributing frames.
Part (I) covers hybrid power and communications wire, typically cross-listed as a composite of both Type NM and Type CM.
800.182. Communications Raceways. Parts (A), (B), and (C) cover communications raceways, one for each basic level of the hierarchy. As previously noted, the use of one of these raceways does not relieve the installer of the responsibility to pull in communications cables with equivalent fire resistance into the raceway. For example, a plenum communications raceway in an air-handling plenum cavity per 300.22(C) must have CMP cabling pulled into it.
810.1. Scope. This article covers antenna systems for radio and television reception, and amateur radio transmission. The article does not cover equipment that couples signaling impulses to power line conductors.
810.4. Community Television Antenna. The antenna of such a system is covered here. Any coaxial distribution is covered under Art. 820.
810.5. Radio Noise Suppressors. This equipment must be listed and in a protected location.
810.11. Material. Except as used for a short lead-in (under 11 m or 35 ft), antenna and lead-in conductors must be hard drawn copper or other high-strength, corrosion-resistant material.
810.12. Supports. Outdoor antennas must be securely supported and not attached to a service mast, or any pole or similar structure carrying power circuits over 250 V line-to-line. Insulators must be strong enough to secure the antenna and the lead-in must be securely attached to the antenna.
810.13. Avoidance of Contacts with Conductors of Other Systems. For service drops and conductors on the exteriors of buildings, the requirements for insulating covering and methods of installation depend on the likelihood of crosses occurring between signal conductors and light or power conductors. Antenna wiring must be kept where it will not come into contact with power wiring, and a 600-mm (2-ft) minimum spacing is required.
810.14. Splices. The antenna may unavoidably be so located that in case of a break in the wire, it may come in contact with electric light or power wires. For this reason, the wire should be of sufficient size to have considerable mechanical strength. Splices must be made so the conductors are not appreciably weakened.
810.15. Grounding. Masts and metal structures supporting antennas must be grounded as covered in 810.21. This includes antennas for satellite TV reception.
810.16. Size of Wire-Strung Antenna—Receiving Stations. For wire-strung antennas, Table 810.16(A) gives the minimum AWG sizes based on span. Part (B) covers self-supporting antennas, including the ones for satellite TV reception. Here again they must be located away from overhead power drops.
810.17. Size of Lead-In—Receiving Station. The tensile strength of a lead-in must at least equal to that of the antenna in 810.16.
810.18. Clearances—Receiving Station. Lead-ins must not swing closer than 600 mm (2 ft) to power circuits up to 250 V wire-to-wire, and not within 3 m (10 ft) of higher voltage wiring. If the wiring is tied down on insulators or otherwise secured and not over 150 V between conductors, the spacing can come down to 100 mm (4 in.). A lead-in must never be closer than 1.8 m (6 ft) to a lightning down conductor. Underground lead-ins must be at least 300 mm (12 in.) from power, lighting, or Class 1 circuits, unless either the power side or the lead-in side is run in a raceway or metal cable armor.
Part (B) covers the lead-ins where they run indoors. In this case the separation is 50 mm (2 in.), also allowed closer if the systems are permanently separated through the use of fixed nonconductors or the power side is using metal raceways or cable armor. The wiring can enter the same box as long as a permanently installed barrier keeps the systems apart.
810.19. Electrical Supply Circuits Used in Lieu of Antenna—Receiving Stations. The coupling device between the supply circuit wiring and the antenna leads must be listed.
810.20. Antenna Discharge Units—Receiving Stations. Every lead-in conductor from an outdoor antenna must be provided with a listed antenna discharge unit, unless it is enclosed in a continuous metallic shield that is grounded per 810.21, or protected with its own antenna discharge unit. Antenna discharge units must be located as near as practicable to the point of entrance into the building they protect, and ahead of any radio set. They must be grounded in accordance with 810.21.
810.21. Grounding Conductors—Receiving Stations. Grounding conductors must comply with (A) through (K).
The NEC requires the grounding conductor to be made of copper (or other corrosion resistant material), and stranded or solid. Insulation is not required and it can run inside or outside the building. The size must be no smaller than 10 AWG (or 8 AWG aluminum, or 17 AWG bronze or copper-clad steel). It must run in as straight a line as practical, securely fastened in place, and be guarded from physical damage. If run in a metal raceway, both ends must be bonded even though 250.64(E) only imposes that requirement on ferrous raceways. The grounding electrode can also be used as an operating ground station activity.
Part (F) covers electrode terminations. If there is an intersystem bonding termination, then the termination is to that point. If the intersystem bonding point is lacking but there are one or more grounding electrodes, the connection must be made to that grounding system through one of the optional methods listed. If the premises served have no intersystem bonding termination and no grounding electrode system, then the bonding connection is to the nearest traditional building electrode (water pipe, building steel, concrete-encased electrode, ground ring), and if all those are missing then to a 1.5 m (5 ft) ground rod, driven into permanently damp soil to the extent practicable, using connections that comply with 250.70.
810.52. Size of Antenna. The minimum size of antenna conductors for ham radio transmission/reception operations is given in Table 810.52, which is also the size of the lead-in as specified in 810.53.
810.54. Clearance on Building. Antenna conductors must be firmly mounted at least 75 mm (3 in.) clear of the surface wired over, and the lead-in conductors must observe the same clearance. If, however, coaxial cable (“continuous metal shield”) is used for the lead-in, the clearance rule disappears provided the coaxial cable shield is grounded to the station grounding conductor as covered in 810.58.
810.55. Entrance to Building. If a coaxial cable with a 810.58 grounding connection is not used for the lead-in wire, the lead-in conductor must enter through an insulating nonabsorbent tube or bushing, or through an opening arranged so the entrance wires can be firmly secured with a 50-mm (2-in.) clearance, or through a drilled hole in a pane of glass.
810.56. Protection Against Accidental Contact. Antenna lead-ins must be positioned so inadvertent contact with them would be difficult.
810.57. Antenna Discharge Units—Transmitting Stations. Every lead-in must have an antenna discharge unit, or other suitable method to drain off static charge. This could be as simple as a connection to the station ground when the station is not operating.
810.58. Grounding Conductors—Amateur Transmitting and Receiving Stations. The grounding conductors must comply with the minimum provisions of 810.21, with the size no smaller than as in 810.21(H), but also no smaller than the lead-in. The operating grounding conductor must not be smaller than 14 AWG.
810.70. Clearance from Other Conductors. All station conductor wires must be at least 100 mm (4 in.) from power or signaling wiring, unless separated from them with a securely fastened insulator such as a porcelain tube or loom. This section also has an exception, not in the form of a complete sentence and therefore of uncertain meaning, pointing to Art. 640. This exception is probably obsolete. It was in the NEC over 50 years ago when Art. 640 was firmly rooted in the vacuum tube era, and it is unlikely to have any meaning with today’s technology.
810.71. General. Transmitters must be enclosed in a grounded metal enclosure, and any external controls must have their operating handles connected to an equipment grounding conductor as well, if the controls are accessible to operating personnel, assuming the transmitter is powered from the premises wiring system, or grounded using the 810.21 system if otherwise. The transmitter enclosure doors must have interlocks that will shut down any voltages above 350 between conductors when any access door opens.
820.2. Definitions. A coaxial cable is a cylindrical assembly comprising a central signaling conductor surrounded by a dielectric and then set within a metallic tube or shield, and usually covered by an insulating jacket.
Exposed (to Accidental Contact) applies to a CATV cable that is in such a position that it would be likely to become energized in the event that a support or insulation or both failed.
Point of Entrance is the point within a building at which cable emerges from an external wall, or a floor slab, or from RMC or IMC connected to a grounding electrode by a grounding conductor as covered in 820.100(B). In such cases the use of heavy-wall steel conduit artificially extends the point of entrance into a building, doing for this wiring what 230.6 does for service entrance conductors. This is an important concept, and as previously noted in Art. 800, it holds for all of Chap. 8.
820.15. Power Limitations. Coaxial cable on systems within the scope of this article is permitted to provide up to 60 V in the process of providing limited power to some equipment directly associated with the system.
820.21. Access to Electrical Equipment Behind Panels Designed to Allow Access. It is contrary to the NEC to drape endless quantities of these cables across suspended ceiling panels in a way that limits the intended access to the ceiling cavity above them.
820.24. Mechanical Execution of Work. In addition to the usual neat and work-manlike manner requirement, this section also requires exposed cabling (which includes the area above a suspended ceiling) to be supported to structure such that normal building operations will not damage the cable. In addition, if the wiring is run parallel to framing, it must meet the 32-mm (1¼-in.) spacing requirement from the leading edge of the framing. Finally, the wiring must stay off the tie wires designed to support a suspended ceiling, in accordance with 300.11.
820.25. Abandoned Cables. This has the effect of requiring that any “abandoned” conductors—as defined in 820.2 as not being terminated or identified for future use with a tag—must be removed. It is no longer permissible to leave abandoned CATV cables in place when they are no longer in use, unless they have been “identified” for future use.
820.26. Spread of Fire or Products of Combustion. This is a restatement of 300.21, as applied to this article.
820.44. Overhead Communications Wires and Cables. Parts (A) and (B) cover pole and drop work and require CATV wires to run below power wiring on the same pole if practicable, and never attached to the same cross arm. The climbing space is to be as required in 225.14(D), and there must be a minimum of 300 mm (12 in.) separation from power wiring at any point in a span, including at their point of attachment at the load end. This reduced spacing only applies if the spacing at the pole meets the required 1 m (40 in.) spacing on the pole.
Part (C) covers coaxial cables to run up a mast on its outside if it is “intended for the attachment and support of such cables.” This can never include a service mast, for which 230.28 absolutely disallows any connections thereto except the service drop conductors. This prohibition is accurately conveyed in the statement of the rule.
Part (D) covers rooftops, and the default clearance is 2.5 m (8 ft), with exceptions for auxiliary buildings such as garages, and also for mast applications and steep roof applications that exactly duplicate the comparable exceptions for service drops operating at not over 300 V.
Part (E) covers interbuilding runs, and requires secure supports at the points of attachment. The exception following provides for messenger in the event the span is too much for the CATV on its own.
Part (F) covers wiring on the outside of buildings. The CATV cabling must be not less than 100 mm (4 in.) from non-power-limited circuits, or else separated with some fixed nonconductive barrier. In addition, the CATV wiring must be routed to avoid interference with adjacent communications wiring. Finally, cables on buildings must avoid separations of less than 1.8 m (6 ft) from lightning protection system conductors wherever practicable.
820.47. Underground Circuits Entering Buildings. Where in manholes with power circuits, barriers must be arranged to create a separate section for the communications circuits. Direct-buried cables must be separated not less than 300 mm (12 in.) from direct-buried non-power-limited circuits, such as service laterals run as single-conductor Type USE. If the power circuits are in a recognized wiring method, either raceway or recognized cable assembly including multi-conductor Type USE or jacketed Type MC listed for direct burial, then the spacing rule does not apply.
820.48. Unlisted Cables and Raceways Entering Buildings. Unlisted outside plant cables may enter a building and move through general purpose spaces (not risers or plenums) up to 15 m (50 ft) from the point of entrance. This allows a transition length along which a convenient point can be provided for a transition to the listed cables required for most interior work. If such a point is unavailable, the point of entrance can be artificially extended through the use of grounded heavy-wall steel conduit.
820.93. Grounding of the Outer Conductive Shield of Coaxial Cables. This rule is split into a termination outside or inside a building, but the action to be taken is the same in either event: Make a grounding connection as covered in 820.100 as near as practicable to the point of entry. Here again that point of entry can be extended through the use of conduit. Part (C) covers a primary protector, should one be installed (not required as of this Code). If used, it must be listed and applied at the point of entrance. And, per (D), it must not be located in a hazardous (classified) location.
820.100. Cable and Primary Protector Grounding. Both the protector and any metallic members of a cable sheath must be grounded in accordance with the rules of this section.
Part (A) requires the grounding conductor to be listed and insulated, made of copper (or other corrosion resistant material), and stranded or solid. The size must be no smaller than 14 AWG. It must run in as straight a line as practical, and be guarded from physical damage. If run in a metal raceway, both ends must be bonded even though 250.64(E) only imposes that requirement on ferrous raceways. It must be as short as practicable and not over 6 m (20 ft) in one-and two-family dwellings. If the 6-m (20-ft) limitation can’t be met, place an additional electrode as covered in 820.100 and then bond this electrode to the power system electrode with a 6 AWG or larger copper wire.
Part (B) covers electrode terminations. If there is an intersystem bonding termination, then the termination is to that point. If the intersystem bonding point is lacking but there is one or more grounding electrodes, the connection must be made to that grounding system through one of the optional methods listed. If the premises served have no intersystem bonding termination and no grounding electrode system, then the bonding connection is to the nearest traditional building electrode (water pipe, building steel, concrete-encased electrode, ground ring), and if all those are missing then to a 1.5-m (5-ft) ground rod, driven into permanently damp soil to the extent practicable, using connections that comply with 250.70.
Part (D) requires that this electrode, although required to be at least 1.8 m (6 ft) distant from other electrodes, must be bonded to the power system grounding electrode system with a conductor no smaller than 6 AWG copper. The power system bonding requirement is presumably waived at mobile homes for which the connection would be impractical. This is the apparent result of the wording of an exception that, in violation of the Style Manual, is not in the form of a complete sentence and therefore unclear as to effect. Refer to the discussion at 820.106 for more information.
Part (E) correlates with 820.93(C) and opens the door to protective devices that are being developed to shunt excessive shield currents so the shields do not incinerate in response to current imposed by a failure in a power system neutral with the coaxial shield running in parallel and fully accessible through the electrode bonding rules. These devices divert 60 Hz current while blocking high frequency current, thereby keeping the principal function of the cable shielding in operation.
820.103. Equipment Grounding. This section specifically recognizes that the coaxial shield is an equipment grounding conductor when connected to the equipment being supplied by it.
820.106. Grounding of Entrance Cables at Mobile Homes. This is very difficult to follow, unless you factor in the wording in the first paragraph of 820.93. Specifically, mobile homes are supposed to have a bonding terminal on their chassis at an accessible location, as required in 550.16(C)(1). They are also supposed to have either service equipment or a feeder disconnect located within 9.0 m (30 ft), per 550.32(A). If they have actual service equipment at that location, or if they have a feeder disconnect with a regrounded neutral at that point, there will be a grounding electrode system connected at that disconnect. In fact, even if the disconnect does not include a regrounded neutral, 250.32(A) still requires a grounding electrode connection at this point. Assuming the communications cable entry comes from this location, a bonding connection between the conductive elements in the communications cable and the grounding system at the disconnect will meet all requirements and no further action needs to be taken at the mobile home. If, and only if, the disconnect is located at an excessive distance or grounded incorrectly does the necessity of creating a local electrode at the mobile home kick in. The philosophical context for this rule is at 800.90(B), second paragraph.
This brings up the separate question of bonding. If the mobile home is permanently connected to a code compliant disconnect, then the permanent equipment grounding system connecting the mobile home and the disconnect is sufficient for these purposes. However, if the mobile home is cord- and plug-connected, removing the plug would disrupt this continuity. In this case there is a conundrum because this wording was brought over from 800.106. Article 800 (telephone) systems have primary protectors that will not exist on these systems. That leaves only one option, a grounding electrode, and therefore, through this back door, a local grounding electrode becomes required in the event of a cord- and plug-connection. The grounding electrode must be connected to the conductive elements of the CATV cable, and also to the mobile home bonding terminal as previously mentioned.
820.110. Raceways for Communications Wires and Cables. Raceways can be Chap. 3 methods or CATV raceways as covered later. These raceways are very close to ENT in construction and this section even mandates the use of the installation provisions in Art. 362 having to do with bends, supports, joints, and perhaps most intriguingly, 362.56 which invokes the box-at-termination rules in 300.15. On the other hand, conduit fill limitations do not apply.
820.133. Installation of Communications Wires, Cables, and Equipment. Part (A) sets forth the system separation rules, which are comparable to Art. 725 provisions. Part (A)(1) covers raceways, cable trays, boxes, and cable assemblies, in two headings, the first being uses with other power-limited circuits in race-ways. The context for these rules is that CATV circuits have a voltage exposure that is comparable to power-limited fire alarm or Class 3 signaling circuits. Therefore, the following systems can share an enclosure with communications cables: (1) Class 2 and Class 3 cabling—Art. 725; (2) Power-limited fire alarm wiring—Art. 760; (3) Optical fiber cabling both conductive and nonconductive—Art. 770; (4) Communications systems—Art. 800; and (5) Low-power network-powered broadband communications—Art. 830.
The second heading addresses sharing space with non-power-limited circuits, for which the rule is no common locations allowed, but there are two exceptions. The first recognizes a permanent barrier or listed divider. The second exception allows a common enclosure where the power limited and non-power-limited wiring must terminate on the same equipment, as in the case of some powered equipment with a CATV interface. The general solution is to restrain the wiring with duct, tie-downs, or other methods such that a 6-mm (¼-in.) air separation is maintained between systems. Note that this provision is for dead-end wiring only, not daisy chains (“solely for power supply to” does not mean to connect and then to feed another piece of equipment).
Part (A)(2) requires a 50-mm (2-in.) separation from open power wiring and other open, non-power-limited circuit conductors. Two exceptions apply, the first where a raceway on either system provides separation, or where the non-power limited wiring uses Chap. 3 cabled wiring methods. The second applies where fixed barriers such as porcelain tubes or flexible tubing are installed.
Note that even though this rule does not expressly cover the topic, Type NMS cable relies on this concept, and UL has listed this sort of hybrid cable for many years, as expressly covered in 334.116(C). Such cable assemblies do not depend on conductor insulation alone to establish the required system separation, squarely in accordance with the spirit of these rules; however, the literal text of this wording is in direct conflict with the Chap. 3 permission.
Part (B) covers conductor support and states that cables must not be tie-wrapped to or otherwise supported by electrical raceways, as also disallowed in 300.11(B). However, there is an exception for coaxial cables to run up a mast on its outside if it is “intended for the attachment and support of such cables.” This can never include a service mast, for which 230.28 absolutely disallows any connections thereto except the service drop conductors. The correct statement of this rule is found at 820.44(C).
820.154. Applications of Listed Communications Wires and Cables and Communications Raceways. Part (A) covers plenum cavity applications, and requires Type CATVP cabling. Included here are listed plenum signaling raceways, provided only the plenum grade cabling is pulled in to them. Listed wires and cabling that comply with 300.22(C) are also permitted on the reasonable supposition that power wiring acceptable by right in these areas can also be used for power-limited applications.
Part (B) covers riser applications, defined as penetrating runs of more than one floor (floor to floor can be a lesser grade). This requires Type CATVR cabling at a minimum. Listed riser signaling raceways containing only CATVR cabling are also permitted. In accordance with the general hierarchy discussion in Chap. 7 at 725.154, plenum cavity methods in (A) can also be used. Other listed wiring from lower levels in the hierarchy, or Chap. 3 wiring, is permitted if installed in metal raceways, or in a fireproof chase with firestops at every floor. Lower levels in the hierarchy are also permitted, including those with the “X” suffix, in one- and two-family dwellings.
Part (C) covers general (“other”) wiring in buildings not covered in (A) and (B). The basic method is the cabling without a suffix, as in Type CATV. The lesser residential grade CATVX is permitted where (1) in raceways or other Chap. 3 wiring, or (2) in nonconcealed spaces not over 3 m (10 ft), or (3) in one-or two-family dwellings if not over 10 mm ( in.) in diameter even if concealed, or (4) in multifamily dwellings if limited to 10-mm (-in.) diameter and nonconcealed spaces.
Part (D) covers cable tray applications. Type CATV, CATVR, CATVP, are available for this use. General purpose signaling raceways, likewise with the higher grades available for substitution, are also permitted in cable trays.
Part (E) presents graphically the cable hierarchy.
820.179. Coaxial Cables. This section covers the listing requirements for the cables used in the applications just covered, as follows:
Part (A) covers Types CATVP for plenum cavity applications.
Part (B) covers Type CATVR for riser applications.
Part (C) covers Type CATV for general purpose applications.
Part (D) covers Type CATVX for limited use in residential applications.
820.182. CATV Raceways. Parts (A), (B), and (C) cover CATV raceways, one for each basic level of the hierarchy. As previously noted, the use of one of these raceways does not relieve the installer of the responsibility to pull in CATV cables with equivalent fire resistance into the raceway. For example, a plenum grade CATV raceway in an air-handling plenum cavity per 300.22(C) must have CATVP cabling pulled into it.
830.1. Scope. These systems are being designed and implemented to provide a combination of voice, audio, video, data, and interactive services. Powering, grounding, bonding, and electrical protection issues for these new systems had not been adequately addressed in the NEC articles that heretofore covered communications systems. As explained in the fine print note, the systems typically involve a cable that supplies some power from the network as well as signal to a network interface unit, which converts the broadband signal to their components, such as voice, data, video, etc. The second fine print note calls attention to the exclusions in 90.2(B)(4) that apply to some facilities of communications utilities
Exposed to Accidental Contact with Electrical Light or Power Conductors. This is a similar definition to that in Art. 800, but there are differences. The defined term is much more specific than the general term “Exposed” in Art. 830, and the possibility of contact could occur through a failure of a support or of insulation; Art. 830 requires both elements to fail.
Fault Protection Device. This is an electronic device intended for personnel protection. It is used with low power network-powered broadband communications circuits, and in the event of a fault such as a cable short or open condition, it limits the current and/or voltage and provides acceptable protection from shock.
Network Interface Unit (NIU). This is the device that breaks the broadband signal into its component parts, such as voice, data, and video. It also isolates the network power from the premises signal circuits. It may, but does not necessarily, contain primary and secondary protectors. See Fig. 830-1 for application.
Fig. 830-1. Network Interface Units are where the component signals are separated. (Sec. 830.2).
Network-Powered Broadband Communications Circuit. The circuit extending from the communications utility’s serving terminal or tap up to and including the NIU. A power system analogy might be a service drop or lateral, plus the associated service entrance conductors and ending at the service disconnect. There are important differences, however, in terms of how far and under what conditions the respective circuits can enter a building, based on the relative degree of risk posed by the different systems. A note describes how a typical single-family circuit would fit into the requirements.
830.3. Other Articles. This section covers the application of other articles, and incorporates a generic hazardous (classified) location reference. Section 300-22, and specific references to other material as appropriate for specific circuits derived from the NIU. The two items in Chap. 8 include Art. 800 for communications, and Art. 820 for CATV and for radio distributions, unless protection has been arranged in accordance with Sec. 830.90(B)(3) in the output side of the NIU. Three items apply in Chap. 7, including Art. 770 for optical fiber cables, Art. 760 for power-limited fire alarm circuits, and Art, 725 for Class 2 and Class 3 signaling circuits.
830.15. Power Limitations. This sets the allowable power limitations for low and medium power circuits. Both systems share a 100 VA maximum power rating, but the medium power source can be up to 150 V, as opposed to the 100 V limitation on the low power source. In addition to the table, a dc source as high as 200 V is permitted within the medium power classification, provided its maximum current to ground is 10 mA.
The table limitations for this circuit are identical to those for a Class 3 “Not Inherently Limited” circuit except there isn’t any maximum current nameplate rating specified for the power source, due to the potential drop that normally occurs along a service transmission line. To accommodate this variation in potential, the Network Interface Units (NIUs), amplifiers, and other utility equipment are designed to operate over a wide range of supply voltages. The supply current to the equipment varies inversely as the voltage.
For example, an NIU connected at a point on the transmission line where the potential is 50 V would require twice the current of an NIU connected at a point where the potential is 100 V, but the input volt ampere rating of both would be the same and is not to exceed 100 VA. In addition to the 100 VA rating, the required 100 ÷ V overcurrent protection (or equivalent) limits the current to 100 ÷ V.
The low power source is figured as the likely source for a single-family dwelling, perhaps for an existing CATV subscriber, and the medium power source for similar occupancies with greater functionality or for multiple NIUs or for greater distances from the transmission lines. As proposed, there was originally a high power source option with a 150-V limit (same as medium power) but a 2250-VA power limit. High power cable is a coaxial construction with a grounded shield and 600-V insulation on the center conductor which provide a high level of mechanical protection and electrical isolation of the center conductor. During the comment period there were serious technical issues raised regarding some of the details and the panel elected to proceed with the new article (1999 NEC) but only after stripping out the high power provisions.
830.21. Access to Electrical Equipment Behind Panels Designed to Allow Access. It is contrary to the NEC to drape endless quantities of these cables across suspended ceiling panels in a way that limits the intended access to the ceiling cavity above them.
830.24. Mechanical Execution of Work. In addition to the usual neat and work-manlike manner requirement, this section also requires exposed cabling (which includes the area above a suspended ceiling) to be supported to structure such that normal building operations will not damage the cable. In addition, if the wiring is run parallel to framing, it must meet the 32-mm (1¼-in.) spacing requirement from the leading edge of the framing. Finally, the wiring must stay off the tie wires designed to support a suspended ceiling, in accordance with 300.11.
830.25. Abandoned Cables. This has the effect of requiring that any “abandoned” conductors—as defined in 830.2 as not being terminated or identified for future use with a tag—must be removed. It is no longer permissible to leave abandoned network-powered broadband communications cables in place when they are no longer in use, unless they have been “identified” for future use.
830.26. Spread of Fire or Products of Combustion. This is a restatement of 300.21, as applied to this article.
830.40. Entrance Cables. Both the equipment and the cables used on these systems need to be listed for the purpose, although there is the usual cable substitution table (Table 830.154) that allows a better cable to substitute for a lesser one. The first exception, however, grandfathers all CATV system coaxial cables installed per Art. 820 before Jan. 1, 2000 for low power usage.
Although the subsections following essentially cover the usual four-tier hierarchy for this type of cabling (-P, -R, -, -X), there are some interesting gaps. There isn’t a BMP cable, for example, so medium-power cabling installed in plenum cavities would go back to Sec. 300-22(c) wiring methods. In addition, there isn’t a BLR cable, so running low power systems in a riser would require the better grade BMR cable normally identified with medium power applications.
Part (A) covers running cable on poles and the wording follows 820.44(A). Where practicable, these cables should run below any non-power-limited circuits, and they are forbidden to run on a common crossarm.
Part (B) gives the climbing space requirement, which follows Sec. 800-44(A)(3).
Part (C) rule and its exception corresponds to 820.44(B). Note that the exception includes the 40-in. separation at the pole unlike 800.44(A)(4) where it is in regular text.
Part (D) provides a set of grade clearances based on NESC dimensions. Neither Art. 800 nor Art. 820 have any required clearances from grade. They run somewhat lower than similar dimensions in. 225.18, which is appropriate because they are supposed to run below power conductors where practicable.
Part (E) points to Table 680.8 for its pool clearances.
Part (F) gets its clearances over roofs straight out of 820.44(D) for similar applications.
Part (G) covers the final span requirement, which came directly from the 1996 version of 230.9. It needs to be correlated with important changes to that section subsequently that added what is now 230.9(B).
Part (H) covers runs between buildings; the wording comes directly from 820.44(E).
Fig. 830-2. Higher power levels leads to enhanced protection rules [Sec. 830.44(I)(4); 830.47].
Part (I) covers cabling routed on buildings. The first three paragraphs come directly from 820.44(F), and the fourth paragraph was added. It requires protecting network-powered broadband communications cables from damage, to a height of 8 ft from grade, as shown in Fig. 830-2. The exception (another incomplete sentence) recognizes that the use of a listed fault protection device to the circuit provides an acceptable level of protection from electric shock. With this level of protection on a low power network-powered broadband communications circuit, the mechanical protection requirements can be relaxed without sacrificing safety.
830.47. Underground Circuits Entering Buildings. Due to somewhat greater power levels on these systems, this section includes an additional set of requirements based on the 1996 NEC version (uncorrelated with 1999 and subsequent changes) of 300.5 for physical protection of underground power circuits, including a requirement to protect direct-buried cables that make a transition to above grade by using raceway or equal to the point of entrance (or at least to a height of 8 ft).
The section comes with a burial depth table similar to Table 300.5 but greatly simplified and with many burial depths reduced. There is an exception here, like the one in 830.44(I)(4), that waives the mechanical protection requirements if there is a fault protection device on a low-power circuit. The last subsection, Part (D), picks up what is now the second sentence of 680.10 for underground clearances to swimming pools. Since the rule points to the entire section in Art. 680, the entire rule in 680.10 applies, including the 2008 modification requiring the raceway system to be complete and not just a sleeve.
830.90. Primary Electrical Protection
Part (A) includes the requirements for installing primary protectors for broadband circuits run as unprotected aerial circuits. This is a simplified version of 800.90(A), although without the requirement for protection at each end of an interbuilding circuit with a lightning exposure. This presumably reflects an expectation that these circuits principally involve utility-to-customer connections under the control of utilities, given the “network powered” nature of these systems, and not premises-wired PBX equivalents. However, the section does go on to capture both fine print notes (unenforceable, of course) from 800.90(A), the second of which is appropriately modified by deleting the provision covering the likelihood of interbuilding exposures.
Part (B) is based on 800.90(B). The text has been revised to reflect the presence of the NIU and the options for providing primary protection, on the network side of the NIU, incorporated within the NIU, or on the derived circuits (output side of the NIU). The options help to resolve technical problems, such as signal attenuation by a protector placed on the network-side broadband cable, while providing identical electrical protection and safety. Mobile homes are protected just as they are in Sec. 800.90(B).
Part (C) works within the context of hazardous (classified) locations and limits the placement of either a primary protector or other equipment serving that function, in the same way as 800.90(C).
830.93. Grounding or Interruption of Metallic Members of Network-Powered Broadband Communications Cables. This is based on 820.93. The text has been revised to accommodate additional metallic cable members “not used for communications or powering.” These members must be either grounded or interrupted by an insulating joint or equivalent device. A coaxial cable shield is part of the signal path and cannot be interrupted. Therefore, the rule requires grounding for coaxial cable shields, and permits all other noncommunications or nonpower conductors to be either grounded or interrupted. This approach is also applied in 800.93. A paragraph addresses mobile homes to clarify the treatment of metallic members in those locations.
830.100. Cable, Network Interface Unit, and Primary Protector Grounding. These grounding rules were directly modeled on the equivalent language in what is now Sec. 800.100 and Sec. 800.106.
The only difference is that instead of just referring to primary protectors, the text also refers to NIUs with protectors and NIUs with metallic enclosures as requiring grounding according to the rules in this part. In addition, 830.100(A)(3), in addition to setting 14 AWG as the minimum size (also true in Art. 800), additionally requires that the size be such that its current-carrying capacity be approximately equal to that of the grounded metallic member(s) and protected conductor(s) of the cable, but it need not be larger than 6 AWG.
830.106. Grounding and Bonding at Mobile Homes. This is very difficult to follow, unless you factor in the wording in the second paragraph of 830.93. Specifically, mobile homes are supposed to have a bonding terminal on their chassis at an accessible location, as required in 550.16(C)(1). They are also supposed to have either service equipment or a feeder disconnect located within 9.0 m (30 ft), per 550.32(A). If they have actual service equipment at that location, or if they have a feeder disconnect with a regrounded neutral at that point, there will be a grounding electrode system connected at that disconnect. In fact, even if the disconnect does not include a regrounded neutral, 250.32(A) still requires a grounding electrode connection at this point. Assuming the network-powered broadband communications cable entry comes from this location, a bonding connection between the conductive elements in the cable and the grounding system at the disconnect will meet all requirements and no further action needs to be taken at the mobile home. If, and only if, the disconnect is located at an excessive distance or grounded incorrectly does the necessity of creating a local electrode at the mobile home kick in. The context for this rule is at 830.90(B), second full paragraph just above (C).
This brings up the separate question of bonding. If the mobile home is permanently connected to a code compliant disconnect, then the permanent equipment grounding system connecting the mobile home and the disconnect is sufficient for these purposes. However, if the mobile home is cord- and plug-connected, removing the plug would disrupt this continuity. In this case there is a conundrum because this wording was brought over from 820.106. Article 800 (telephone) systems have primary protectors that will not exist on these systems. That leaves only one option, a grounding electrode, and therefore, through this back door, a local grounding electrode becomes required in the event of a cord- and plug-connection. The grounding electrode must be connected to the conductive elements of the network-powered broadband communications cable, and also to the mobile home bonding terminal as previously mentioned.
830.110. Raceways for Low- and Medium-Power Network-Powered Broadband Communications Cables. Low- and medium-power network-powered broadband cables in a raceway must use a Chap. 3 type, installed according to its requirements in Chap. 3, however, no conduit fill limitations will apply to low-power cables.
830.133. Installation of Network-Powered Broadband Communications Cables and Equipment. Part (A)(1) includes the rules regarding separation of broadband cables from other wiring, as illustrated in Fig. 830-3.
Low power network-powered broadband communications circuits are essentially Class 3 circuits. Medium-power network-powered broadband communications circuits are not Class 3 circuits (similar in some ways but not the same; Class 3 status was denied), but they do have a 600-V jacket. With the following principles in mind, the separation rules make sense:
First, low and medium power circuits are permitted in the same raceway.
Second, low power circuits are permitted with the same circuits in raceways as Class 3 circuits in 725.139(E)(5), including power-limited fire alarm, CATV, Class 2 and 3, Art. 800 communications, and both conductive and nonconductive optical fiber.
Fig. 830-3. System separation rules are always important. [Sec. 830.133(A)(1)].
Third, medium power circuits cannot be installed in a common raceway or enclosure with any of those same systems, with the only exception being non-conductive optical fiber.
Fourth, both low power and medium power broadband circuits have to be divorced from non-power-limited wiring entirely, but with the customary exceptions for barriered separations and for entry into an enclosure housing equipment connected to both systems, with a maintained 6-mm (¼-in.) air separation.
Part (A)(2) on system separation for other applications follows the same rules as for similar CATV applications in 820.133(A)(2), with a normal 2-in. separation and allowances for routing the other circuits in independent Chap. 3 wiring methods or raceways, or for the use of raceways or for porcelain or flexible tubing in addition to the insulation on the broadband cabling.
Note that even though this rule does not expressly cover the topic, Type NMS cable relies on this concept, and UL has listed this sort of hybrid cable for many years, as expressly covered in 334.116(C). Such cable assemblies do not depend on conductor insulation alone to establish the required system separation, squarely in accordance with the spirit of these rules; however, the literal text of this wording is in direct conflict with the Chap. 3 permission.
Part (B) is the wording to keep broadband conductors off interior raceways. This wording is based on similar wording used in 820.133(B).
Part (C) invokes 110.3(B); this being Chap. 8 the reference had to be expressly inserted.
830.151. Medium-Power Network-Powered Broadband Communications System Wiring Methods. This section covers wiring methods for medium-power systems. There is no plenum cavity designation medium power cable recognized (that would normally have a “P” suffix) so in such spaces the wiring reverts to Chap. 3 methods in accordance with 300.22(C). Riser uses generally require Type BMR, except in one- and two-family dwellings, or where it ascends through a fireproof shaft with firestops on every floor, or in a metal raceway. General purposes call for Type BM. In addition, there is no limited service medium power cable either, so the usual allowance for an “X” designated cable for one- and two-family use isn’t an option here.
The underground cable (Type BMU) can only enter the building if it is run in rigid or intermediate metal conduit, which act to artificially extend the point of entrance.
830.154. Applications of Low-Power Network-Powered Broadband Communications System Cables. In this case, there is a cable type designed for each exposure. In the three instances medium power cable is available, (BMR, BM, and BMU) it can be substituted for the low-power version. However, there is no multifamily housing permission for even a limited, unconcealed use of BLX.
Part (A) covers plenum cavities, and Type BLP is available, and a lesser grade installed in a compliant raceway per 300.22(C) is also permissible.
Part (B) covers risers, and Type BLR is available, along with the higher plenum grades or higher power riser grade (thus, BLP or BMR). Metal raceways with a lesser grade such as BLX is permitted provided it, or the enclosed cable if the raceway were discontinued, only passes up through a fireproof shaft with firestops on every floor. In one- and two-family dwellings Type BMX is permitted but not over 10 mm ( in.) in diameter.
Part (C) covers general (“other”) wiring in buildings not covered in (A) and (B). The basic method is the cabling without a suffix, as in Type BL. The superior grades BLP and BLX along with the better power grades BMR and BM are also permitted. The lesser residential grade BLX is permitted where (1) in race-ways or other Chap. 3 wiring, or (2) in one- or two-family dwellings if not over 10 mm ( in.) in diameter even if concealed.
The other two paragraphs address cable entries to the building, with Type BLU (for underground use) excluded except in heavy-wall metal conduit, and type BLX allowed only up to 50 ft from the entry point.
A fine print note points out that making use of the 15-m (50-ft) distance from the point of entry for Type BLX cable could easily be problematic from the standpoint of compliance with 830.90(B), which requires a protector as near as practicable to the point of entry.
Part (D) gets you to the allowable cable substitution table, Table 830.154. All cables in the table proposed for substitution for broadband cabling must be coaxial cables.
830.157. Protection Against Physical Damage. This section incorporates the protective requirements in Sec. 300-4.
830.160. Bends. This section, a first in the communications articles, requires that any bends in the cable be made so as not to damage it. This is in Part V, so it only applies indoors.
830.179. Network-Powered Broadband Communications Equipment and Cables. Cables outside and entering buildings must be listed accordingly. Low power circuits get the usual permitted substitutions (see Fig. 830-4) plus the grandfathering in 830.179 Exception No. 1.
Fig. 830-4. Cable substitutions are incomplete for the medium power level. (Sec. 830.179).
There are just two listing sequences in this section, and they leave gaps on the medium power side. The medium power varieties include BMR for risers, BM for general purpose applications and BMU for underground use, leaving the limited residential use and the plenum cavity use without a cable type. On the other hand, the low-power list is fully populated, from the plenum cavity BLP, to the riser BLR, to general purpose BL, to residential limited application BLX, and the underground BLU.
