NEC Grounding/Bonding October 2009
Introduction This course is designed to provide the participant with the necessary understanding of the reasons NEC code discussed in Grounding & Bonding is required on each DIRECTV this course is based off the NEC 2002 code. Satellite System installation. This course provides recommendations with respect to grounding of a DIRECTV Satellite System. The final grounding/bonding method is dictated by State and Local electrical codes. However, the electrical inspectors may require more stringent grounding methods. Important Note: Adherence to these requirements is ultimately the responsibility of the local site or office. Before starting this course, it is recommended that you identify which NEC® code is applicable for your jurisdiction or jurisdictions, if your area covers more than one. 2
Course Objectives Upon completion of this course, you will have an understanding of the following topic areas: Why We Ground “What is the NEC®” Service Reduction DIRECTV Equipment The NEC®, Application for DIRECTV Underwriters Laboratory (UL) explained NEC® Sections Defined NEC® Adoption by State Technician Grounding Scenarios 3
Why do I need this course? There are two reasons for grounding: The first, it is the law; this law is to keep us all safe as well as the customer. The second reason is DIRECTV requires it. Non-compliance causes money wasted on unnecessary truck rolls for service and/or equipment issues. You want job security… do the job right and customers will sell DIRECTV to their friends for us. 4
Why We Ground 5
Why We Ground NEC® 810. 21 (H) Bonding of Electrodes. The #10 AWG wire cannot exceed 20 feet in length. Your specific area may require other wire types as noted by state and local codes. 6
Why We Ground We will discuss in this section the top ten reasons to ground: 1. Limit voltages due to lightning Prevent lightning from striking the dish. NOT to carry the current from a lightning strike safely to ground. Lightning strike spreads energy Preferred path Bonding the ODU 7
Why We Ground 2. Line Surges Source of over-voltage is, in a properly grounded system, provided with an alternative path around the electrical system of your home or workplace by intentionally connecting the system to the earth. Proper grounding of the antenna mast and lead-in cables is somewhat effective in protecting receiving equipment from voltage transients that result from lightning. 8
Why We Ground 3. Unintentional contact with high voltage lines Tornados, high winds, and strong storms can bring power lines down. Power line insulation can wear over time and can come into contact with nearby objects. 9
Why We Ground 4. Dissipate static electricity The satellite ODU sits outside where wind will create a static charge on the dish itself and the wire attached to it. This action is similar to walking across carpet and then touching another object, which causes a difference of potential resulting in transfer of the charge. 10
Why We Ground 5. Potential Difference If the system is not bonded to the main service ground, you could experience an unbalanced ground within the system. Not grounding to the house electrical system leads to a difference in potential between two grounds. 11
Why We Ground 6. Provide a drain for signals and noise captured by the shield Bonding the shield serves to nullify the effects of stray signals by "grounding out, " or reducing to a zero potential, the voltages which are picked up by the outer shield. 12
Why We Ground 7. Ground Loops A ground loop occurs when there is more than one bond connection path between two pieces of equipment. The duplicate bonding paths form the equivalent of a loop antenna, which very efficiently picks up interference currents. Lead resistance transforms these currents into voltage fluctuations. 13
Why We Ground 8. Lawsuits Don’t expose yourself and the company to the consequences of not following the code. Ground/bond all installs in compliance with the applicable code, be it NEC®, state or local. 14
Why We Ground 9. Personal injury Article 90 of the NEC® covers personnel safeguarding of persons and property. This will be covered in the NEC® section 15
Why We Ground 9. Personal injury continued… If the ground used for the coaxial cable, which is also connected to the receiver cabinet, is a better ground than the one used for the electrical service The entire house current could potentially, at least partially, flow back through the receiver’s electrical service ground lead. 16
Why We Ground 10. 1 st and foremost – It’s the LAW 17
Technician Scenario 1: Using a Volt Meter 18
Technician Scenario 1 Using a Volt Meter Volt OHM Meter All VOMs have probes. These probes are color coded red and black and plug in the front of the VOM. The black is the ground or negative and the red is hot or positive. Connecting Leads Most VOMs have 3 plug-in locations on their face for probes. One is common for ground, one is usually marked V for voltage, and the third is marked Ohms or has a symbol Ω. 19
Technician Scenario 1 Reading Voltage The selector switch or dial on the meter should be set to read AC volts and at a setting where the meter can read 110 -125 volts AC. The test probes must be connected into the correct meter inputs, place the red and black probes into the slots identified to the right. Voltage should be approximately 110 v AC. 20
Technician Scenario 1 Caution should always be used when testing the output voltage of an electrical outlet. If you make contact with the exposed ends of the leads an electric shock could occur that could cause injury. Insert the Red and Black probes into the Neutral and Ground positions. The volt meter should register less than 1 v AC, voltage higher than this could indicate improper wiring. 21
Grounding Requirements The length of the #10 AWG grounding wire placed between our ground block and the house grounding electrode system must not exceed 20 feet in length. If the ground block is farther than 20 feet from any part of the grounding electrode system, consider rewiring the cables from the ODU to a new ground block location that is within 20 feet of the ground source. 22
Grounding Requirements Allows for the connection to a grounding electrode system that is more than 20 feet from the ground block, but more equipment is required. An additional ground rod or grounding electrode would need to be installed at the ground block location, and a heavy wire would need to be installed between the additional ground rod and the home’s main electrical system electrode. 23
Grounding Requirements Ground rods installed in addition to the primary ground rod must be bonded to the existing ground rod with a #6 AWG bonding wire Electrical system ground rods must be installed by a licensed electrician 24
Technician Scenario 2: AC Voltage at Ground Block 25
AC Voltage at Ground Block Technician arrives at a service call to find AC voltage on the coaxial cable at the ground block. Suggestions: Disconnect all DIRECTV receivers within the installation Test ALL electrical outlets and consider using a non-contact voltage detector Notify the customer and your supervisor of all electrical issue Follow your company specific SAFETY guidelines! 26
AC Voltage at Ground Block Consider the following items when working around or near any electrical system on any installation inside, outside, attic and the crawl space of any building: Exposed electrical lines or lighting terminals Electrical wiring with deteriorated insulation Electrical fencing 27
AC Voltage at Ground Block Effects of Electric Current in the Human Body Current Reaction Below 1 milliamp Generally not perceptible. 1 milliamp Faint Tingle. 5 milliamps Slight shock felt; not painful but disturbing. Average individual can let go. Involuntary reactions can lead to other injuries. 6 -25 milliamps (women) Painful shock, loss of muscle control. 9 -30 milliamps (men) The freezing current or “let-go” range. 50 -150 milliamps Extreme pain, respiratory arrest, severe muscular contractions. Death is possible 1, 000 -4300 milliamps (1. 0 – 4. 3 amps) Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely. 10, 000 milliamps (10 amps) Cardiac arrest, sever burns; death probable. Information source: W. B. Kouwenhoven, “Human Safety and Electric Shock”, November 1968 28
“What is the NEC®” 29
What is the NEC Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. The NEC® is prepared by the National Electrical Code Committee, which consists of a Technical Correlating Committee and 20 code-making panels. The code-making panels have specific subject responsibility within the Code. The NEC® Code covers the installation of electric conductors, electric equipment, signaling and communications conductors and equipment and fiber optic cables and raceways for the following: Public and private premises, including buildings, structures, mobile homes, recreational vehicles and floating buildings. Yards, lots, parking lots, carnivals and industrial substations. State & Local authorities adopt the NEC® code based on year of release as a guideline; in turn, these authorities can exceed the requirements as dictated by the NEC® code that is adopted for use. The NEC® code may be adopted as an enforceable standard or set of requirements by states, counties and / or municipalities. 30
How does it apply NEC 90. 4 Enforcement This Code is intended to be suitable for mandatory application by governmental bodies that exercise legal jurisdiction over electrical installations, including signaling and communications systems, and for use by insurance inspectors. The authority having jurisdiction for enforcement of the Code has the responsibility for making interpretations of the rules, for deciding on the approval of equipment and materials, and for granting the special permission contemplated in a number of the rules. 31 NEC® Codes are updated every three years Sections are updated, then referenced throughout the code. Current code in effect as deemed by the local authority having jurisdiction. Emphasis is on grounding & bonding. State, county or municipal codes may supersede the NEC®, these are typically more stringent in nature and may outline fees and penalties. Interpretation Many people claim to know the code. There is conjecture among licensed individuals, states, and municipalities. Every reference must be studied to find the true meaning of the code. Rules change from NEC® revision to NEC® revision State and local assertions supersede the NEC®, but are required to be written into law. AHJ is defined as “Authority Having Jurisdiction”, this could be the state or local inspector, who in turn has the final say regarding requirements.
UL & Grounding 32
How does it apply UL stands for Underwriters Laboratories, and is a well-known testing laboratory that develops standards and test procedures for materials. 33
Grounding and Bonding Equipment UL 467 Scope 1. 1 a. This Standard applies to grounding and bonding equipment for use in accordance with the National Electrical Code, NFPA 70 (NEC). b. 1. 2 This Standard applies to the following grounding and bonding equipment: i. ground clamps, bonding devices, grounding bushings, watermeter shunts, grounding electrodes, and the like used in a grounding system; ii. equipment for making electrical connections between the grounding conductors used in electrical power systems, noncurrent-carrying metal parts of electrical equipment, armored grounding wires, metal raceways, and the like; and iii. grounding electrodes; c. equipment for making electrical connections between i. the grounding conductors used in telecommunications systems such as telephone, radio, CATV, network power broadband, and the like; and ii. grounding electrodes; and d. hospital grounding jacks and mating grounding cord assemblies 34
Service Reduction 35
Service Reduction Impact Equipment failure is the number one service reason in the network; typically accounting for more than 31% of all service calls outlined in the Weekly Service Report. 36
Service Reduction Impact Almost 20% of the time the receiver is replaced The information in the graphic above basically translates to: Sites with lower grounding pass rates have higher occurrences of IRD failures. 37 Effective grounding methods have been shown to significantly reduce equipment failure rates.
DIRECTV Equipment 38
The IRD & Voltage The IRD power supply knows it will receive 110 vac with a variance of +/- 5 vac from a typical residential electrical power grid. There is a Schematic for the power supply which shows specific output voltages supplied for electronics inside each receiver. Example of a typical Power Supply. 39
The IRD & Voltage The power supply supplies specific dc voltages for powering of the connected LNB, internal hard drive (for DVR models only) internal tuner(s) and other internal components specific to the receiver. The power supply is designed to dissipate heat generated by the power supply itself. This heat is a factor when the receiver is placed into an area that does not provide for adequate movement of air. Inadequate movement of air then allows premature failure of a receiver. 40
The IRD & Voltage Issues What happens when voltages do not reach the receiver as designed? What happens when unexpected voltages reach the receiver by way of the coaxial cable? Can small voltage fluctuations cause electronic components to fail prematurely overtime? 41
The IRD & Voltage Issues Greater resistance in the installation components, LNB, cabling, etc. can cause the power supply to run at a higher current output mode, which leads to an excessive creation of heat and lower voltage. A typical residential 110 vac power supply runs at 60 Hz. In some instances, faulty electrical equipment can induce harmonics onto the residential power supply, which in turn cause the receiver to loose functionality resulting in pixelization and or signal loss. 42
The IRD & Voltage Issues 43 Harmonics are comparable to resonance that produces overcurrent surges, and is equivalent to continuous audio feedback through a PA system. This can result in destroyed capacitors, fuses, and damaged surge suppressors. Household items such as microwaves, freezer motors, well motors, arc welders and dimmers can induce harmonics onto the power supply for the residence. Approximately 1/3 of the receivers returned are found to have no problems or the problems reported cannot be duplicated, and leads to unneeded costly service calls.
Technician Scenario 3: Intermittent Pixelization 44
Intermittent Pixelization Technician arrives at the service call with a customer complaint of intermittent pixilation. What is the first thing to check? Do you use a circuit tester frequently? Do you use a volt / ohm meter? Do you know how to use the volt / ohm meter correctly? Can you isolate the IRD to another electrical circuit? Do electrical appliances within the customer’s home affect the IRD? Microwaves Freezers Rural homes may have the following: Well Pumps Arc Welders 45
Intermittent Pixelization Focus on IRD Failure Installers and service techs can have an overwhelming impact on service call volume from IRD failures. There are multiple systems at work at the customer’s residence. The first system is the homes electrical system. It is represented by the electrical service line, the power meter, the conduit to the breaker panel, the internal house wiring and the ground wiring. The second system is the DIRECTV system. It is represented by the LNB, the outside wires, ground block, switch, internal house wiring and the ground wiring. Other systems include phone, cable TV and data networks. All of these systems potentially can have different points of ground bonding within the same electrical system. Note: Article 810. 21 (I) Common Ground Reference Common Ground. A single grounding conductor shall be permitted for both protectiveand operating purposes. 46
Intermittent Pixelization Focus on IRD Failure The currents and signals carried by these two separate systems come together at one point; the receiver. Without any grounding at all, the only place these two systems have in common is the receiver. Unexpected voltages on either system will want the same thing; to go to ground. If the electrical system has its own ground source (e. g. an eight foot ground rod), and the DIRECTV system has a separate ground source, unexpected voltages on either system will have a choice of two ground sources. The unexpected voltages will choose whichever source has the least resistance to ground. It could be either one. These voltages can get to either of the two ground sources through the point at which both systems are connected; THE RECIEVER! The transfer of voltage from one system to the other can and will burn the receiver out. This is why it is extremely important to use one common house ground. Note: Article 810. 21 (I) Common Ground Reference Common Ground. A single grounding conductor shall be permitted for both protective and operating purposes. 47
Intermittent Pixelization Focus on IRD Failure If both the home electrical system and the DIRECTV system are grounded to the same point, the unexpected voltages will find that there is only one choice of ground path. This directs all transient voltages through the ground wires, and NOT through the receiver. Correctly grounding our installations to a common ground source will reduce service calls caused by burned out receivers, and increase our customer satisfaction. Our understanding of this basic principle and our ability to ensure its practice in the field is just one example of what sets DIRECTV apart from its competitors, and makes us the industry leader. Note: Article 810. 21 (I) Common Ground Reference Common Ground. A single grounding conductor shall be permitted for both protective and operating purposes. 48
Technician Scenario 4: Tracing a Power Surge through Multiple Grounds 49
Tracing a Power Surge through Multiple Grounds In the event lightening strikes the reflector, the power surge travels along the coaxial cable shielding to the ground block. At the ground block, the potential difference to ground is determined to be less by the power surge if it travels to the receiver and then to the household ground. 50
Technician Scenario 5: Tracing a Power Surge through Multiple Grounds 51
Tracing a Power Surge through Multiple Grounds In the event lightening strikes the main power line, the power surge travels along the main power line to the main meter panel. At the main panel, the potential difference to ground is determined to be less by the power surge if it travels to the receiver by way of the internal household wiring and then to the coaxial cable ground block. 52
Technician Scenario 6: Tracing a Power Surge through a Single Ground 53
Tracing a Power Surge through a Single Ground In the event lightening strikes to the main power line, the power surge travels along the main power line to the main meter panel. At the main panel, the power surge is diverted to the household ground rod. 54
Technician Scenario 7: Tracing Static 55
Tracing Static electricity is the result of an imbalance between negative and positive charges in an object. These charges can build up on the surface of an object until they find a way to be released or discharged. One way to discharge them in a satellite dish installation is to bond the ODU mount/mast to a ground source. 56
NEC® Sections 57
NEC Sections Defined In this topic, we will discuss the NEC® codes sections that are applicable to the satellite DBS service. NEC Articles Article 100 Definitions Article 250 Grounding & Bonding Article 300 Wiring Methods Article 800 Communications Circuits Article 810 Radio and Television Equipment Article 820 Community Antenna Television and Radio Distribution Systems (CATV) 58
Article 100 Definitions 59
Article 100 Definitions Article 100 contains only those definitions essential to the proper application of this Code. It is not intended to include commonly defined general terms or commonly defined technical terms from related codes and standards. In general, only those terms that are used in two or more articles are defined in Article 100. Other definitions are included in the article in which they are used but may be referenced in Article 100. 60
Article 100 Definitions Approved: Acceptable to the authority having jurisdiction. Authority: Having Jurisdiction. The organization, office, or individual responsible for approving equipment, materials, an installation or procedure. Bonding (Bonded): The permanent joining of metallic parts to form an electrically conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed. Bonding Jumper: A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected. 61
Article 100 Definitions Bonding Jumper, Equipment: The connection between two or more portions of the equipment grounding conductor. Bonding Jumper, Main: The connection between the grounded circuit conductor and the equipment grounding conductor at the service. Conductor, Bare: A conductor having no covering or electrical insulation whatsoever. Conductor, Covered: A conductor encased within material of composition or thickness that is not recognized by this Code as electrical insulation. 62
Article 100 Definitions Conductor, Insulated: A conductor encased within material of composition and thickness that is recognized by this Code as electrical insulation. Copper-Clad Aluminum Conductors: Conductors drawn from a copper-clad aluminum rod with the copper metallurgically bonded to an aluminum core. The copper forms a minimum of 10 percent of the cross-sectional area of a solid conductor or each strand of a stranded conductor. Dwelling Unit: One or more rooms for the use of one or more persons as a housekeeping unit with space for eating, living, and sleeping, including permanent provisions for cooking and sanitation. Dwelling, One-Family: A building that consists solely of one dwelling unit. 63
Article 100 Definitions Dwelling, Two-Family: A building that consists solely of two dwelling units. Dwelling, Multifamily: A building that contains three or more dwelling units. Dwelling, MDU: The FCC defines and MDU property as an apartment, condominium or cooperative buildings. In addition, it includes gated communities, mobile home parks, garden communities and other centrally managed residential real estate developments. Enclosure: The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage. 64
Article 100 Definitions Energized: Electrically connected to a source of voltage. Ground: A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth. Grounded: Connected to earth or to some conducting body that serves in place of the earth. Grounded Effectively: Intentionally connected to earth through a ground connection or connections of sufficiently low impedance and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons. 65
Article 100 Definitions Grounded Conductor: A system or circuit conductor that is intentionally grounded. Grounding Conductor: A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes. Grounding Conductor, Equipment: The conductor used to connect the non–current-carrying metal parts of equipment, raceways, and other enclosures to the system grounded conductor, the grounding electrode conductor, or both, at the service equipment or at the source of a separately derived system. 66 Grounding Electrode Conductor: The conductor used to connect the grounding electrode(s) to the equipment grounding conductor, to the grounded conductor, or to both, at the service, at each building or structure where supplied from a common service, or at the source of a separately derived system.
Article 100 Definitions Ground-Fault Circuit Interrupter: A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device. Listed: Equipment, materials, or services included in a list published by an organization that is acceptable to the authority having jurisdiction and concerned with evaluation of products or services, that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services, and whose listing states that the equipment, material, or services either meets appropriate designated standards or has been tested and found suitable for a specified purpose. Outlet: A point on the wiring system at which current is taken to supply utilization equipment. 67 Plenum: A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system.
Article 100 Definitions Power Outlet: An enclosed assembly that may include receptacles, circuit breakers, fuse holders, fused switches, buses, and watt-hour meter mounting means; intended to supply and control power to mobile homes, recreational vehicles, or boats, or to serve as a means for distributing power required to operate mobile or temporarily installed equipment. Premises Wiring (System): That interior and exterior wiring, including power, lighting, control, and signal circuit wiring along with their associated hardware, fittings, and wiring devices, both permanently and temporarily installed, that extends from the service point or source of power. Such wiring does not include wiring internal to appliances, luminaries (fixtures), motors, controllers, motor control centers and similar equipment. 68
Article 100 Definitions Raceway: An enclosed channel of metal or nonmetallic materials designed expressly for holding wires, cables, or bus bars, with additional functions as permitted in this Code. Raceways include, but are not limited to, rigid metal conduit, intermediate metal conduit, flexible metallic tubing, flexible metal conduit, electrical metallic tubing, under floor raceways, cellular concrete floor raceways, cellular metal floor raceways and bus ways. Receptacle: A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke. Service Drop: The overhead service conductors from the last pole or other aerial support to and including the splices, if any, connecting to the service-entrance conductors at the building or other structure. 69
Article 100 Definitions Service Equipment: The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply. Service Point: The point of connection between the facilities of the serving utility and the premises wiring. Ventilated: Provided with a means to permit circulation of air sufficient to remove an excess of heat, fumes, or vapors. Voltage to Ground: For grounded circuits, the voltage between the given conductor and that point or conductor of the circuit that is grounded; for ungrounded circuits, the greatest voltage between the given conductor and any other conductor of the circuit. 70
Article 250 Grounding & Bonding 71
250. 1 Scope This article covers general requirements for grounding and bonding of electrical installations, and specific requirements. Systems, circuits, and equipment required, permitted, or not permitted to be grounded. Circuit conductor to be grounded on grounded systems Location of grounding connections. Types and sizes of grounding and bonding conductors and electrodes. Methods of grounding and bonding. Conditions under which guards, isolation or insulation may be substituted for grounding. 72
250. 8 Connection of Grounding and Bonding Equipment Prohibits the use of sheet metal screws as a means for attaching equipment grounding conductors to equipment. Connection means that are listed, are part of listed equipment, or are exothermically welded are required to ensure a permanent and low-resistance connection 73
250. 8 Update (A)Permitted Methods Grounding conductors and bonding jumpers shall be connected by one of the following means: 1. Listed pressure connectors 2. Terminal bars 3. Pressure connectors listed as grounding and bonding Equipment 4. Exothermic welding process 5. Machine screw-type fasteners that engage not less than two threads or are secured with a nut 6. Thread-forming machine screws that engage not less than two threads in the enclosure 7. Connections that are part of a listed assembly 74
250. 8 Update Non Permitted Methods Connection devices or fittings that depend solely on solder shall not be used. This applies to interior water piping constructed using solder. Sheet metal screws shall not be used to connect grounding conductors to enclosures. 75
250. 8 Update In this cut away example, the Ka. Ku foot plate of the ODU included grounding screw has produced almost 3 full machine type screw threads in the metal. A self-tapping sheet metal screw, which is commonly found in hardware stores, will not comply with the NEC® standard. In this example only, a single thread is formed. 76
250. 10 Protection of Ground Clamps and Fittings Ground clamps or other fittings shall be approved for general use without protection or shall be protected from physical damage as indicated in (1) or (2). 1) In installations where they are not likely to be damaged. 2) Where enclosed in metal, wood, or equivalent protective covering. 77
250. 12 Clean Surfaces Nonconductive coatings, such as paint, lacquer, and enamel, on equipment to be grounded should be removed from threads and other contact surfaces to ensure good electrical continuity or be connected by means of fittings designed so as to make such removal unnecessary. 78
250. 28 Main Bonding Jumper For a grounded system, an un-spliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure to the grounded conductor of the system within the enclosure for each service disconnect. Construction: Where a main bonding jumper is a screw only, the screw shall be identified with a green finish that shall be visible with the screw installed 79
250. 50 Grounding Electrode System Section 250. 50 introduces the important concept of a “grounding electrode system, ” in which all electrodes are bonded together, as illustrated in Exhibit 250. Rather than relying totally on a single electrode to perform its function over the life of the electrical installation, the NEC® encourages the formation of a system of electrodes “if available on the premises. ” There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time. 80
250. 50 Grounding Electrode System Example, Exhibit 250. 50 A grounding electrode system that uses the metal frame of a building, a ground ring, a concrete- encased electrode, a metal underground water pipe, and a ground rod. 81
250. 52 Grounding Electrodes (A) Electrodes Permitted for Grounding 1. 2. Metal Frame of the Building or Structure: The metal frame of the building or structure, where effectively grounded. 3. 82 Metal Underground Water Pipe: A metal underground water pipe in direct contact with the earth for 3. 0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Concrete-Encased Electrode: An electrode encased by at least 50 mm (2 in. ) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.
250. 52 Grounding Electrodes (A) Electrodes Permitted for Grounding 3. 4. 83 Ground Ring: A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6. 0 m (20 ft) of bare copper conductor not smaller than 2 AWG. Rod and Pipe Electrodes: Rod and pipe electrodes shall not be less than 2. 5 m (8 ft) in length and shall consist of the following materials. 1. Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.
Technician Scenario 8: Grounding Decision 84
Grounding Decision Your job is to draw a line representing the ground bonding wire from the ground block to the proper grounding location. Your decision is based on NEC® sections 250. 8, 250. 52 (A)(1) as well as the “ 20 ft” rule (Section 800. 40). 85
250. 52 Grounding Electrodes (A) Electrodes Permitted for Grounding 5. 6. 86 Rod and Pipe Electrodes: Rod and pipe electrodes shall not be less than 2. 5 m (8 ft) in length and shall consist of the following materials. a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of iron or steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection. Plate Electrodes: Each plate electrode shall expose not less than 0. 186 m² (2 ft 2) of surface to exterior soil. a) Electrodes of iron or steel plates shall be at least 6. 4 mm (1/4 in. ) in thickness. Electrodes of nonferrous metal shall be at least 1. 5 mm (0. 06 in. ) in thickness.
250. 52 Grounding Electrodes 6. 87 Other Local Metal Underground Systems or Structures: Other local metal underground systems or structures such as piping systems and underground tanks.
250. 52 Grounding Electrodes (B) Electrodes Not Permitted for Grounding The following shall not be used as grounding electrodes: 1. Metal underground gas piping system 2. Aluminum electrodes 88
250. 70 Methods of Grounding and Bonding Conductor Connection to Electrodes. 89 The grounding or bonding conductor shall be connected to the grounding electrode by exothermic welding, listed lugs, listed pressure connectors, listed clamps, or other listed means. Connections depending on solder shall not be used. Ground clamps shall be listed for the materials of the grounding electrode and the grounding electrode conductor and, where used on pipe, rod, or other buried electrodes, shall also be listed for direct soil burial or concrete encasement. Not more than one conductor shall be connected to the grounding electrode by a single clamp or fitting unless the clamp or fitting is listed for multiple conductors One of the following methods shall be used: A pipe fitting, pipe plug, or other approved device screwed into a pipe or pipe fitting. A listed bolted clamp of cast bronze or brass, or plain or malleable iron. For indoor telecommunications purposes only, a listed sheet metal strap-type ground clamp having a rigid metal base that seats on the electrode and having a strap of such material and dimensions that it is not likely to stretch during or after installation. An equally substantial approved means.
250. 92 Services (A) Bonding of Services 1. 90 Intended to clarify where metal raceways, boxes, or enclosures contain a grounding electrode conductor. Both ends of the raceway, box, or enclosure must be bonded to the grounding electrode conductor. a) Bonding the raceway to the conductor reduces the impedance and minimizes the potential difference between the electrical equipment and ground.
250. 94 Bonding for Other Systems An accessible means external to enclosures for connecting intersystem bonding and grounding conductors shall be provided at the service equipment and at the disconnecting means for any additional buildings or structures by at least one of the following means: 1. Exposed nonflexible metallic raceways 2. Exposed grounding electrode conductor 3. Approved means for the external connection of a copper or other corrosionresistant bonding or grounding conductor to the grounded raceway or equipment 4. FPN 91
Technician Scenario 9: Potential Difference 92
Potential Difference The technician has line of sight on the east side of the house. The solitary outlet is on the east side of the house. An external service equipment enclosure is on the east side of the house and services the air conditioning unit. 93
Potential Difference Can we attach to the “service enclosure” on/for the AC unit under NEC 250. 94? Ask yourself, how is the service enclosure grounded? The AC unit service enclosure is not compliant because of what factors? 94
Article 800 Communications Circuits 95
800. 1 Scope Article 800 covers telephone, telegraph (except radio), outside wiring for fire alarm and burglar alarm, and similar central station systems; and telephone systems not connected to a central station system but using similar types of equipment, methods of installation, and maintenance. 96
800. 40 Cable and Primary Protector Grounding The metallic member (s) of the cable sheath, where required to be grounded by 800. 33, and primary protectors shall be grounded as specified in 800. 40(A) through (D). (A) Grounding Conductor Length: The primary protector grounding conductor shall be as short as practicable. In one- and two-family dwellings, the primary protector grounding conductor shall be as short as practicable, not to exceed 6. 0 m (20 ft) in length. Run in Straight Line: The grounding conductor shall be run to the grounding electrode in as straight a line as practicable. 97
800. 100 Cable and Primary Protector Grounding The primary protector and the metallic member (s) of the cable sheath shall be grounded as specified in 800. 100(A) through (D). (A) Grounding Conductor Length: The primary protector grounding conductor shall be as short as practicable. In one-and two-family dwellings, the primary protector grounding conductor shall be as short as practicable, not to exceed 6. 0 m (20 ft) in length. FPN: Similar grounding conductor length limitations applied at apartment buildings and commercial buildings help to reduce voltages that may be developed between the building’s power and communications systems during lightning events. Run in Straight Line: The grounding conductor shall be run to the grounding electrode in as straight a line as practicable. 98
Technician Scenario 10: LOS & Grounding Location 99
LOS & Grounding Location “You are driving up that country driveway toward the home where you are going to install DIRECTV. As it comes into view, what first thoughts come to mind in regards to the important job variables you must consider? ” 100
LOS & Grounding Location The number one technician response is “Line of Sight” Let’s expand on your answer. You should think of both LOS and…“Where is the grounding point? ” The cable (ground block) must come to within 20 ft of the grounding electrode system in order to make the installation compliant with the National Electric Code. So…this may ultimately change our choice of ODU mounting location. 101
Article 810 Radio and Television Equipment 102
810. 1 Scope Article 810 covers antenna systems for radio and television receiving equipment, amateur radio transmitting and receiving equipment, and certain features of transmitter safety. This article covers antennas such as multi-element, vertical rod, and dish, and also covers the wiring and cabling that connects them to equipment. This article does not cover equipment and antennas used for coupling carrier current to power line conductors. Article 810 covers wiring requirements for television and radio receiving equipment, specifically including digital satellite receiving equipment for television signals, and wiring for amateur radio equipment. 103
810. 3 Other Articles Wiring from the source of power to and between devices connected to the interior wiring system shall comply with Chapters 1 through 4 other than as modified by Parts I and II of Article 640. Wiring for audio signal processing, amplification, and reproduction equipment shall comply with Article 640. Coaxial cables that connect antennas to equipment shall comply with Article 820. 104
810. 4 Community Television Antenna The antenna shall comply with this article. The distribution system shall comply with Article 820. 105
810. 15 Grounding Masts and metal structures supporting antennas shall be grounded in accordance with 810. 21. 106
810. 16 Size of Wire-Strung Antenna — Receiving Station (B) Self-Supporting Antennas. Outdoor antennas, such as vertical rods, dishes, or dipole structures, shall be of corrosion-resistant materials and of strength suitable to withstand ice and wind loading conditions. They shall be located well away from overhead conductors of electric light and power circuits of over 150 volts to ground, so as to avoid the possibility of the antenna or structure falling into or making accidental contact with such circuits. 107
810. 18 Clearances - Receiving Stations ·Underground conductors shall be separated at least 12" from conductors of any light or power circuits. · 4” Separation of attached lead-in power line conductors and coaxial cable. · 6’ Separation of lightening arrest systems and coaxial cables. 108
810. 18 Clearances - Receiving Stations The clearance between lead-in conductors and any conductor forming a part of a lightning rod system shall not be less than 1. 8 m (6 ft) unless the bonding referred to in 250. 60 is accomplished. Underground conductors shall be separated at least 300 mm (12 in. ) from conductors of any light or power circuits or Class 1 circuits. 109 ·Underground conductors shall be separated at least 12" from conductors of any light or power circuits. · 4” Separation of attached lead-in power line conductors and coaxial cable. · 6’ Separation of lightening arrest systems and coaxial cables.
810. 20 Antenna Discharge Units — Receiving Stations A. Where Required Each conductor of a lead-in from an outdoor antenna shall be provided with a listed antenna discharge unit. Exception: Where the lead-in conductors are enclosed in a continuous metallic shield that either is permanently and effectively grounded or is protected by an antenna discharge unit. B. Location Antenna discharge units shall be located outside the building or inside the building between the point of entrance of the lead-in and the radio set or transformers and as near as practicable to the entrance of the conductors to the building. 110
810. 21 Grounding Conductors - Receiving Stations C. Material The grounding conductor shall be of copper, aluminum, copper-clad steel, bronze, or similar corrosion-resistant material. Aluminum or copper-clad aluminum grounding conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad aluminum shall not be installed within 450 mm (18 in. ) of the earth. 111
810. 21 Grounding Conductors - Receiving Stations D. Supports The grounding conductors shall be securely fastened in place and shall be permitted to be directly attached to the surface wired over without the use of insulating supports. 112
810. 21 Grounding Conductors - Receiving Stations E. Run in Straight Line The grounding conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable from the mast or discharge unit to the grounding electrode. 113
810. 21 Grounding Conductors - Receiving Stations F. Electrode The grounding conductor shall be connected as follows: 1. To the nearest accessible location on the following: a. The building or structure grounding electrode system as covered in 250. 50 b. The grounded interior metal water piping systems, within 1. 52 m (5 ft) from its point of entrance to the building, as covered in 250. 52 c. The power service accessible means external to the building, as covered in 250. 94 d. The metallic power service raceway e. The service equipment enclosure, or f. The grounding electrode conductor or the grounding electrode conductor metal enclosures; or 2. If the building or structure served has no grounding means, as described in 810. 21(F)(1), to any one of the individual electrodes described in 250. 52 3. If the building or structure served has no grounding means, as described in 810. 21(F)(1) or (F)(2), to an effectively grounded metal structure or to any of the individual electrodes described in 250. 52. 114
810. 21 Grounding Conductors - Receiving Stations G. Inside or Outside Building The grounding conductor shall be permitted to be run either inside or outside the building. H. Size The grounding conductor shall not be smaller than 10 AWG copper, 8 AWG aluminum, or 17 AWG copper-clad steel or bronze. I. Common Ground A single grounding conductor shall be permitted for both protective and operating purposes J. Bonding of Electrodes 115 A bonding jumper not smaller than 6 AWG copper or equivalent shall be connected between the radio and television equipment grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used.
Technician Scenario 11: 17 AWG CCS 116
17 AWG CCS Technician arrives at a formal installation to find no dual coaxial cable with copper clad steel messenger used for bonding of the ODU footplate. 117
17 AWG CCS Can the technician attach a separate 17 AWG CCS messenger wire to the existing coaxial run? o The NEC code is concerned about bonding the ODU mount and mast to the residential ground source: there is nothing that prohibits attaching the 17 AWG CCS messenger to the coaxial cable. – If zip ties are used, black colored are recommended for outdoor use and they should be staggered at unequal distances to… – Zip ties should not be tight or should avoid compromising the integrity of the… 118
Article 820 Community Antenna Television and Radio Distribution Systems (CATV) 119
820. 1 Scope This article covers coaxial cable distribution of radio frequency signals typically employed in community antenna television (CATV) systems. Article 820 covers the installation of coaxial cable for the distribution of radio frequency (RF) signals associated with closed-circuit television, cable television, and security television cameras. This article also covers interior coaxial cable for radio and television receiving equipment. 120
820. 33 Grounding of Outer Conductive Shield of a Coaxial Cable The outer conductive shield of the coaxial cable shall be grounded at the building premises as close to the point of cable entrance or attachment as practicable. For purposes of this section, grounding located at mobile home service equipment located in sight from, and not more than 9. 0 m (30 ft) from, the exterior wall of the mobile home it serves, or at a mobile home disconnecting means grounded in accordance with 250. 32 and located in sight from and not more than 9. 0 m (30 ft) from the exterior wall of the mobile home it serves, shall be considered to meet the requirements of this section. 121
820. 40 Cable Grounding Where required by 820. 33, the shield of the coaxial cable shall be grounded as specified in 820. 40(A) through (D). A. Grounding Conductor 1) Insulation: The grounding conductor shall be insulated and shall be listed as suitable for the purpose. 2) Material: The grounding conductor shall be copper or other corrosion-resistant conductive material, stranded or solid. 3) Size: The grounding conductor shall not be smaller than 14 AWG. It shall have a current-carrying capacity approximately equal to that of the outer conductor of the coaxial cable. The grounding conductor shall not be required to exceed 6 AWG. 4) Length: The grounding conductor shall be as short as practicable. In one- and two-family dwellings, the grounding conductor shall be as short as practicable, not to exceed 6. 0 m (20 ft) in length. 5) Run in Straight Line: The grounding conductor shall be run to the grounding electrode in as straight a line as practicable. 122
820. 42 Bonding and Grounding at Mobile Homes A. Grounding Where there is no mobile home service equipment located in sight from, and not more than 9. 0 m (30 ft) from, the exterior wall of the mobile home it serves or there is no mobile home disconnecting means grounded in accordance with 250. 32 and located within sight from, and not more than 9. 0 m (30 ft) from, the exterior wall of the mobile home it serves, the coaxial cable shield ground, or surge arrester ground, shall be in accordance with 820. 40(B)(2). 123
820. 42 Bonding and Grounding at Mobile Homes (B) Bonding The coaxial cable shield grounding terminal, surge arrester grounding terminal, or grounding electrode shall be bonded to the metal frame or available grounding terminal of the mobile home with a copper grounding conductor not smaller than 12 AWG under any of the following conditions: (1) Where there is no mobile home service equipment or disconnecting means as in 820. 42(A). (2) Where the mobile home is supplied by cord and plug. 124
820. 42 Bonding and Grounding at Mobile Homes 125
820. 42 Bonding and Grounding at Mobile Homes 126
820. 49 Fire Resistance of CATV Cables Coaxial cables installed as wiring within buildings shall be listed as being resistant to the spread of fire in accordance with 820. 50 and 820. 51. 820. 50 Listing, Marking, and Installation of Coaxial Cables. Coaxial cables in a building shall be listed as being suitable for the purpose, and cables shall be marked in accordance with Table 820. 50. The cable voltage rating shall not be marked on the cable. 127
820. 51 Additional Listing Requirements Cables shall be listed in accordance with 820. 51(A) through (D). 1. Type CATVP: Type CATVP community antenna television plenum cable shall be listed as being suitable for use in ducts, plenums, and other spaces used for environmental air and shall also be listed as having adequate fireresistant and low smoke-producing characteristics. 2. Type CATVR: Type CATVR community antenna television riser cable shall be listed as being suitable for use in a vertical run in a shaft or from floor to floor and shall also be listed as having fire-resistant characteristics capable of preventing the carrying of fire from floor to floor. 128
820. 52 Installation of Cables and Equipment A. Separation from Other Conductors 1. Other Applications. Coaxial cable shall be separated at least 50 mm (2 in) from conductors of any electric light, power, Class 1, non-power-limited fire alarm, or medium power network-powered broadband communications circuits Exception No. 1: Where either… 1. All of the conductors of electric light, power, Class 1, non –power-limited fire alarm, and medium power networkpowered broadband communications and circuits are in a raceway, or in metal-sheathed, metal-clad, nonmetallicsheathed Type AC or Type UF cables, or 2. All of the coaxial cables are encased in raceway. 129
820. 100 Cable Grounding The shield of the coaxial cable shall be grounded as specified in 820. 100(A) through (D). (A) Grounding Conductor 1. Insulation: The grounding conductor shall be insulated and shall be listed. 2. Material: The grounding conductor shall be copper or other corrosion-resistant conductive material, stranded or solid. 3. Size: The grounding conductor shall not be smaller than 14 AWG, have a current-carrying capacity approximately equal to that of the outer conductor of the coaxial cable, and should not be required to exceed 6 AWG. 130
820. 100 Cable Grounding 4. Length: In one- and two-family dwellings, the grounding conductor shall be as short as practicable, not to exceed 6. 0 m (20 ft) in length. Run in Straight Line. The grounding conductor shall be run to the grounding electrode in as straight a line as practicable. Physical Protection: The grounding conductor shall be protected where exposed to physical damage. Where the grounding conductor is run in a metal raceway, both ends of the raceway shall be bonded to the grounding conductor or the same terminal or electrode to which the grounding conductor is connected. 131
Practical Use Ground Strap Copper on Copper Galvanized on Galvanized Installed in such away as to avoid loosening Bonding wire insulation removed and bent in a clockwise direction to allow multiple points of contact as shown 132
Practical Use Split Bolt To be used to bond the #10 copper bond wire to the primary ground #6 copper or # 6 braided copper Corner Clamps Can not be used on a service/meter door Can not impede access to the equipment inside the enclosure Must fit securely Can not be removed by hand Pipe Clamps Clamp must be identified for the size of pipe Single wire use Copper on Copper Galvanized on Galvanized 133
Practical Use Screw Down Attachments Switches, Splitters, Ground Blocks are for single wire use only Ground Screws Mounted in ODU foot plate If the proper size hole is not present a drill bit of proper size must be used Self forming machine thread Must form at least two threads into the metal housing Green in color (used for QC audit verification) Single wire use 134
Practical Use 135 Pole Mount Installing a fine thread screw on a pole used for pole mounting is not compliant If a screw is used, the bonding wire would contact the pole at two points; the top and the bottom. Attaching the bonding wire with an existing bolt would not be compliant. Currently, the only approved method for bonding a pole mount is to attach the #17 AWG bonding wire at the pole using a ground strap.
NEC Code Adoption Map This map represents those state adoptions of the NEC code by year as of August 2009. 136 For more information, use the following internet link: schneider-electric. us
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