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For EC&M Magazine
By Mike Holt, NEC® Consultant
Do you know the requirements for wiring antenna systems and connecting them to equipment with coax?
Article 810 contains the requirements for wiring television and radio receiving equipment. Article 820 contains the requirements for installing the coaxial cables that connect this equipment [810.3 and 4]. Article 820 doesn't apply to communications utility equipment [90.2(B)(4), 820.1 Informational Note].‚Figure 01
For Articles 800, 810, and 820, the difference between a bonding conductor and a grounding electrode conductor is shown in NEC Informational Note Figures 800(a) and 800(b). A similar Note is located before the Scope of Article 820 as well..
Antenna systems for receiving equipment
Outdoor antennas and lead-in conductors must be securely supported, and the lead-in conductor must be securely attached to the antenna. Don't attach antennas or lead-in conductors to the electric service mast [810.12].
Lead-in conductors must be at least:
- 6 ft from the lightning protection system. Underground antenna lead-in conductors must maintain a separation of at least 12 in. from electric power conductors [810.18(A)].
- 2 in. from electrical power conductors, if they are indoor conductors [810.18(B)].
But separation isn't required where the antenna lead-in conductors or the electric power conductors are in raceways or cable armor.
A lead-in conductor:
- (If from an outdoor antenna) must have a listed antenna discharge unit 810.20(A)]. This unit must be near the point of entrance, but not near combustible material or in a hazardous (classified) location.
- (If indoors) can be in the same enclosure with electric power conductors where separated by an effective, permanently installed barrier [820.18(C)].
- (If attached to a building) must be installed so it can't swing closer than 2 ft to the conductors of circuits of 250V or less, or closer than 10 ft to the conductors of circuits of over 250V [810.18(A)].
Bonding conductors and grounding electrode conductors must meet the requirements of 810.21(A) through 810.21(K). For example, the conductor must be run in as straight a line as practicable [810.21(E)].
Transceiver antennas
The requirements for antenna systems for amateur and citizen band transmitting/receiving stations are in Part III of Article 810 [810.51]. But these systems must also comply with three Part II requirements:
- Antennas and lead-in conductors must be securely supported, and the lead-in conductor must be securely attached to the antenna [810.12].
- Outdoor antennas and lead-in conductors must be kept at least 2 ft from exposed electric power conductors [810.13].
- Outdoor masts and metal structures that support antennas must be grounded per 810.21 [810.15].
Antenna lead-in conductors must be firmly mounted at least 3 in. away from the surface of the building [810.54].
Each lead-in conductor from an outdoor antenna must have a listed antenna discharge unit or other suitable means to drain static charges from the antenna system [810.57], unless:
- The lead-in is protected by a continuous metallic shield grounded per 810.58, or
- The antenna is grounded per 810.58.
The operating bonding conductor or grounding electrode conductor for transmitting stations must be at least 14 AWG copper or its equivalent 810.58(C)].
Coaxial cables
Article 820 focuses on the distribution of television and radio signals via cable, rather than their transmission or reception via antenna. These signals are limited energy, but they're high frequency.
Coaxial cable can deliver power at a maximum of 60V to equipment that's directly associated with the radio frequency distribution system [820.15].
Ensure cables don't prevent removing suspended-ceiling panels for access to equipment [820.21]. This is part of installing coaxial cables in a neat and workmanlike manner, as required by 820.24. Secure coaxial cables to structural components of the building using straps, staples, cable ties, hangers, or similar fittings designed and installed so as not to damage the coaxial cable.
Coaxial cables installed through or parallel to framing members or furring strips must be protected where they're likely to be penetrated by nails or screws. To protect them, install the cables at least 1¼ in. from the nearest edge of the framing member or furring strips. Or protect the cables with a 116 in. thick steel plate or the equivalent [300.4(D)].
Raceways that contain coaxial cables must be securely fastened [820.24, 300.11(A)]. Where above a suspended ceiling, the ceiling support wires or the ceiling grid can't be used for support but adding independent support wires secured at both ends can per 300.11(B) is permitted for securing both coaxial cable and raceways containing coaxial cable.
The accessible portion of coaxial cable not terminated at equipment, and not identified for future use with a tag, must be removed [820.25]. Cables in concealed raceways aren't considered accessible.
Coaxial cables and communications raceways and equipment must be installed in a way that does not substantially increase the spread of fire or products of combustion [820.26]. Openings in fire-rated walls, floors, and ceilings for coaxial cables and communications raceways must be firestopped to maintain the fire resistance rating of the fire-rated assembly. Firestop material is listed for the specific types of wiring methods and construction structures.
Coaxial cables entering buildings
Underground coaxial cables in a duct, pedestal, handhole enclosure, or manhole that contains electric light, power, or Class 1 or nonpower-limited fire alarm circuit conductors must be in a section permanently separated from such conductors by means of a suitable barrier [820.47(A)].
Direct-buried coaxial cable must be separated at least 12 in. from conductors for light or power [820.47(B)], unless electric light or power conductors or coaxial cables are in a Chapter 3 wiring method.
Coaxial cables supplied to a building must have the metallic sheath members bonded and/or grounded as close as practicable to the point of entrance per 820.100 [820.93(A)].
Grounding
For systems using coaxial cables that don't exit the building and are isolated from outside cable systems, the shield can be grounded by a connection to an equipment grounding conductor per 250.118. This connection can be made through a grounded receptacle using a dedicated bonding jumper and a permanently connected listed device [820.100 Ex].
For all other systems, the outer conductive shield of a coaxial cable must be bonded or grounded and the bonding conductor or grounding electrode conductor must be [820.100]:
- Listed.
- Copper or other corrosion resistant conductive material.
- As short as practicable. For one and two family dwellings, the bonding conductor or grounding electrode conductor must not exceed 20 ft.
- Run in as straight a line as practicable.
- Mechanically protected where subject to physical damage; where installed in a metal raceway, each end of the raceway must be bonded to the bonding conductor or grounding electrode conductor.
And the bonding conductor or grounding electrode conductor must be at least 14 AWG. Connect the bonding conductor or grounding electrode conductor per 820.100(B)(1), (B)(2), or (B)(3). For example, if it's in a building with an intersystem bonding termination it must terminate to that termination.
If a separate grounding electrode is installed for the CATV system, bond it to the building's power grounding electrode system with a 6 AWG or larger conductor [820.100(D)].
Installing within buildings
Any coaxial cable longer than 50 ft from its point of entrance must be listed [820.113(A) Ex, 820.48].
Plenum rated coaxial cables can be installed within ducts specifically fabricated for environmental air spaces per 300.22(B) if the cable is directly associated with the air distribution system. But the cable must be plenum rated with a length as short as practical to perform the required function, or in a raceway per 300.22(B) [820.113(B)].
Only specific kinds of wires, cables, raceways, and cable routing assemblies are permitted in other spaces used for environmental air as described in 300.22(C). These are identified in 820.113(C)(1) through (7).
Only specific kinds of cables can be:
- Supported by cable trays; those are identified in 820.113(H).
- Installed in building locations other than the locations covered in 820.113(B) through (I); those are identified in 820.113(J).
- Installed in one- and two-family, and multifamily dwellings in locations other than the locations covered in 820.113(B) through (I); those are identified in 820.113(K).
Reducing cost
Articles 810 and 820 are often used as a pair, because the person installing the antenna system often installs the coaxial cable that connects it to the equipment. It's best to review both articles before starting any phase of the installation. Considering not just equipment and antenna location but how you are going connect the two can save considerable money on the installation.
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