Presentation on theme: "Grounding FTTH Systems at the Home"— Presentation transcript:
1 Grounding FTTH Systems at the Home May 8, 2012Presented by:Dean L. Mischke, P.E.Finley Engineering Company, Inc.
2 DisclaimerThe following presentation is the opinion of Dean Mischke and has not been verified with NFPA or IEEE.
3 Reference Materials 2012 National Electric Safety Code (C2-2012 NESC) Administered by IEEEApproved by American National Standards Institute (ANSI)Covers Distribution NetworkNew Edition every 5 years (next one due 2017)
4 Reference Materials 2011 National Electric Code (NEC) Administrated by National Fire Protection Agency (NFPA)Covers Premise WiringNew Edition every 3 yearsRead the 2011 NEC online at:View the document online (read only)View the 2011 edition online
6 Purpose of Grounding and Bonding Primary function of grounding and bonding is the protection of the customer and maintenance personnel from lightning, induced voltages, or direct contact with electrical supply circuits.Secondary Function of grounding and bonding is to reduce the amount of damage the communication facilities from lightning, induced voltages, or direct contact with electrical supply circuits.Finally, to comply with NEC and NESC.
7 OSP Grounding & Bonding Issues: NESC Section 2 Definitions Effective ground/effectively grounded: Bonded to an effectively grounded neutral conductor or to a grounding system designed to minimize hazard to personnel and having resistance to ground low enough to permit prompt operation of circuit protection devices.Restricted Access: Where exclusive control is maintained.
8 Rule 099 Additional Requirements for Communications Apparatus OSP Grounding & Bonding Issues: NESC Section 9 Grounding methods for electrical supply and communications facilitiesRule 099 Additional Requirements for Communications ApparatusB. The Communications grounding conductor shall not be less than #6 AWG; however, owner preference may be largerC. Bonds between communication ground rods and electrical supply neutral rods shall not be required to be greater than #6 AWG
9 Important Sections of National Electric Code (NEC) Article 90 IntroductionArticle 100 DefinitionsArticle 250 Grounding and BondingArticle 480 Storage BatteriesArticle 770 Optical Fiber Cables and RacewaysArticle 800 Communications CircuitsArticle 820 Community Antenna Television and Radio Distribution SystemsArticle 830 Network-Powered Broadband Communications SystemsArticle 840 Premise-Powered Broadband Communications Systems
10 Bonding Conductor Term Change in NEC The term Grounding Conductor has been replaced by Bonding Conductor or Grounding Electrode Conductor where applicable
13 Copper Communication Circuits within Buildings Copper Communication Circuits are defined as low voltage communication circuits including voice, audio, video, data, interactive services, alarm, etc.The rules governing copper communications circuits are dependant on how the service is derived:If the service is derived from another building, Article 800If the service is derived from a Network Powered fiber-fed device, Article 830If the service is derived from a Premise Powered fiber-fed device, Article 840
14 NEC Article 830 Network Powered Broadband Systems Article 830 covers Coaxial Cable powered broadband systems, composite coaxial and twisted pair, or composite fiber with conductors with power.In summary all of the previous rules apply for metallic cable entering the buildingServices voice/data and video must comply with rules in Articles 770, 800, and 820Introduces the Network Interface Unit (NIU) as the device that derives the component voice, data, and video signals at the premise.Power Limitations are specified in (1) and (2) and Table (see next slide)Medium power systems entering the building shall use Type BMU, BM, or BMR Cable (A)Low power systems entering the building shall uses Type BLU or BLX cables or approves substitutions in Table (b) (B)
15 NEC Article 830 Network Powered Broadband Systems
16 NEC Article 830 Network Powered Broadband Systems 1Vmax, Imax, and VAmax are determined with the current-limiting impedancein the circuit (not bypassed) as follows:Vmax—Maximum system voltage regardless of load with rated inputapplied.Imax—Maximum system current under any noncapacitive load, includingshort circuit, and with overcurrent protection bypassed ifused. Imax limits apply after 1 minute of operation.VAmax—Maximum volt-ampere output after 1 minute of operationregardless of load and overcurrent protection bypassed if used.2Overcurrent protection is not required where the current-limiting deviceprovides equivalent current limitation and the current-limitingdevice does not reset until power or the load is removed.
17 NEC Article 840 Premise Powered Broadband Systems Article 840 is new for 2011 and covers premise-powered optical fiber broadband systems that provides any combination of voice, video, data, and interactive services through an ONT.The Article becomes the starting point for communications circuits derived from premise-powered, fiber-fed ONTs.Introduces the Optical Network Terminal (ONT) as the device that derives the component voice, data, and video signals at the premise.
18 NEC Article 840 Premise Powered Broadband Systems Article 840: Definition of exterior or interior rated ONTAll exterior ONTs are required to be grounded/bonded as per the requirements of their UL listingThis applies regardless if the ONT is installed indoors or outdoorsInterior ONTs typically do not require to be grounded/bonded per the requirements of their UL listingI am not aware of any indoor ONTs that can be installed outdoors
19 NEC Article 840 Premise Powered Broadband Systems Article ONT and Fiber Cable GroundingServices voice/data and video must comply with rules in Articles for the fiber, for the copper communications cables, and for the coaxial cables
20 NEC Article 770 Fiber Optic Cable within Buildings Article 770 Scope: Applies to the installation of fiber optical cable, raceways, and optical cable assembliesConductive Fiber Optic Cable: A factory assembly under an overall covering comprised with non-metallic and metallic non-current carrying members (metallic sheath or strength members) 770.2Non-Conductive Fiber Optic Cable: A factory assembly under an overall covering that is comprised entirely of non-conductive members 770.2Composite cables (copper conductors under the same sheath of optical fibers) shall be classified in accordance of the type of electrical conductors 770.3(B)
21 NEC Article 770 Fiber Optic Cable within Buildings Article Unlisted Cables Entering BuildingsConductive and Non-Conductive fiber optic cable may be installed in building spaces other than risers, ducts used for environmental air, plenum used for environmental air (some building code inspectors include in this definition any suspended ceiling with ducted air) must terminate within 50’ from the point of entry (A)The point of entrance is defined in as the emergence through:Exterior wallConcrete floor slabRigid Metal Conduit (must run to exterior wall)Intermediate Metal Conduit (must run to exterior wall)
22 NEC Article 770 Fiber Optic Cable within Buildings Article Unlisted Cables Entering BuildingsUnlisted Non-Conductive fiber optic cable may be installed in raceway as long as the raceway complies withArticle 342 Intermediate Metallic Conduit, Type IMCArticle 344 Rigid Metal Conduit, Type RMCArticle 352 Rigid Polyvinyl Chloride Conduit, Type PVCArticle 358 Electrical Metallic Tubing, Type EMT
23 NEC Article 770 Fiber Optic Cable within Buildings Article Grounding or Interruption of Non-Current Carrying Metallic Members of Fiber Optic CableEntering Buildings: Cable exposed to contact with electric light or power conductors shall be either grounded as specified in Article or interrupted by an insulating joint as soon as possible at the point of entry (A)Terminating On The Outside of a Building: Cable exposed to contact with electric light or power conductors shall be either grounded as specified in Article or interrupted by an insulating joint as soon as possible at the point of termination (B)
24 NEC Article 770 Fiber Optic Cable within Buildings Article Grounding of Non-Current Carrying Metallic Members of Fiber Optic CableBonding Conductor or Electrode Grounding Conductor shall belisted and shall be either insulated covered, or bare (A)(1)Minimum size of 14 AWG and shall not be required to be larger than #6 AWG (Note the 2012 NESC calls for a # 6 AWG in all cases, given the conflict, it will be best to standardize on the # 6)Run in a straight lineMust be done in accordance to Article 250Protected from damageSee Bonding and Grounding in Article 800
25 NEC Article 800 Copper Cable within Buildings Article Cable and Primary Protector Grounding. The metallic member(s) of the cable sheath, were required by Section , and primary protectors shall be grounded as specified in (a) though (d)a. Grounding Conductor. The grounding conductor shall be (A)1. Listed and insulated, covered, or bare2. Copper or other corrosion-resistant conductor, solid or stranded.3. Size shall not be less that the current carrying capacity of the sheath or current carrying conductors but not less than 14 AWG and shall not be required to exceed #6 AWG (Note the 2012 NESC will call for a # 6 in all cases. In addition, RUS also calls for an insulated #6))4. Length of less than 20 feet. Runs greater than 20 feet require a ground rod as identified in (B)(2) and bonded to the service entrance ground rod with a #6 conductor as specified in (D).5. Run in a straight line.6. Protected from damage
26 NEC Article 800 Copper Cable within Buildings Article Continuedb. Electrode. The grounding electrode shall be connected as follows (B)1. To the nearest accessible location on the following:a. The building structural grounding electrode system as covered in Sectionb. The power service accessible means external to enclosures as covered in Section Exceptionc. Metallic service racewaye. The service equipment enclosuref. The grounding electrode conductor or the grounding electrode conductor metal enclosure of the power systemg. To the grounding conductor or the grounding electrode of a building or structure disconnecting means that is grounded to an electrode as covered in Section
27 NEC Article 800 Copper Cable within Buildings Article ContinuedC. Electrode Connection. Connections to grounding electrodes shall comply with SectionD. Bonding of Electrodes. A bonding jumper not smaller than # 6AWG shall be connected between the communications grounding electrode and power grounding electrode system.Exception for Mobile Homes see
28 NEC Article 800 How Many Ground Rods?? (A)(4) sets maximum length to 20’The Exception allows for a communications ground rod, then bonding as specified in (D)(D) in essence states that you must bond with a #6 AWG with no reference for additional ground rodsGrounding ConductorGrounding Conductor100’Bonding Conductor
29 NEC Article 800 Reference to Article 250 NEC Article 800 Reference to Article Copper Cable within BuildingsArticle Methods of Grounding Conductor Connection to Electrodes: The grounding conductor shall be connected to the grounding electrode byexothermic weldinglisted lugs, pressure connectors, clamps, or other listed means.Connections depending on solder shall not be used.Grounding clamps shall be listed for the materials in the grounding electrode and grounding electrode.Clamps in contact with the soil shall be rated for direct burial.No more than 1 conductor per clamp unless the clamp is listed for more conductors.
30 NEC Article 820 Coax Cable within Buildings Article 820 covers Coaxial Cable providing a CATV type service wiring within the building.In summary all of the previous rules apply for shielded cable entering the buildingCoaxial cable must have a primary protector and be grounded and bonded as described in the pervious sections if the cable is attached to the outside of the building or leaves the buildingNew for 2011, for coaxial cable that does not leave the building, Article Exception allows the cable to be grounded from the equipment; however, the equipment must be grounded to a grounded receptacle that has a dedicated grounding conductor. A cord and plug is not acceptable. The net result of this code is that none of the ONTs are provisioned to accept this kind of ground so a coaxial ground is still required.
31 NEC Article 840 Premise Powered Broadband Systems Article Premise Circuits Not Leaving the Building: Where the ONT is served by a nonconductive fiber optic cable or where the metallic non-current carrying elements are interrupted by an insulating joint or equivalent device, and the ONT and it’s circuits are entirely contained within the building.Almost impossible to assure that wiring will always remain in buildingIs wiring under vinyl siding still contained within the building?
32 NEC Article 840 Premise Powered Broadband Systems Article Premise Circuits Not Leaving the Building: ContinuedCommunication Circuit Grounding is not required (B)If the communication circuit goes to the outside of the building, then Article , which references Article will apply.If the circuit stays under the requirements in Article Informational Notes (1-3), then the circuit does not need primary protection
33 NEC Article 840 Premise Powered Broadband Systems Article Premise Circuits Not Leaving the Building: ContinuedONT Grounding: The ONT is not required to be grounded unless required as part of it’s UL listing. If the coaxial cable is used and it is grounded as described in (A)(1) or (A)(2), the ONT can be connected with a plug and cord (C)Where required to be grounded and the ONT is grounded to a receptacle, the size of the grounding conductor is specified in specified in
34 NEC Article 840 Copper Cable within Buildings Article Primary Protector Grounding and Bonding at Mobile Homes(A) Grounding:(1) If there is no electrical service entrance located within 30 ft. of the exterior wall of the mobile home it serves, the ONT, if required to be grounded, shall be connected to a grounding electrode conductor or grounding electrode in accordance with(2) Where there is no mobile home disconnecting means grounded in accordance with and located within 30 ft. of the exterior wall of the mobile home it serves, the ONT, if required to be grounded, shall be connected to a grounding electrode in accordance with (B)(3).
35 NEC Article 840 Copper Cable within Buildings Article Primary Protector Grounding and Bonding at Mobile Homes(B) The ONT grounding terminal or grounding electrode shall be connected to the metal frame or available grounding terminal of the mobile home with a copper conductor not smaller than # 6 AWG under any of the following conditions.(1) Where there is no mobile home service disconnecting means as in (A)(2) When the mobile home is supplied by a cord and plug.
36 Ground ClampsClamps designed to clamp on the outside of the meter box may be not approved in your area.
37 Ground ClampsClamp designed to Screw on to the Front Cover of a Service Entrance Box. It is UL ListedI recommend that you do not allow this clamp. The notes for NEC (B)(2) specifically state that the bonding device is not allowed to connect to any removable part and cannot be installed on the door or cover, even if it is not removable.
38 Customer Premise Grounding & Bonding Issues: General Recommendations Make all attempts to ground the communication system with a insulated #6 AWG conductor in order of preference as follows:1. Clamp to the service entrance grounding electrode conductor or ground rod. Note: You cannot cut the service grounding conductor to install your ground!!2. Clamp to the metal aerial or buried electrical service entrance mast. Clean contact points down to bare metal to insure a good ground. Repaint if required after the clamp is in place.3. Clamp to the service entrance box inside the premise.
39 Customer Premise Grounding & Bonding Issues: General Recommendations Do Not use the following:1. Exposed Conduit or copper water pipe: With the increasing use of plastic in the electrical and plumbing industry, neither grounding point can provide a reliable ground reference. While the ground may work today, there is no assurance that plastic will not be used in the future breaking the communication ground path.Always place a permanent tag at the point connection with the electrical ground. The tag should contain the following:1. “Communication Ground Do Not Remove”2. Company Name3. Trouble Report Telephone NumberBond the sheath at the pedestal and customer premiseFor Off-Premise Extensions, bond the sheath at the initial protector. Isolate the sheath at the outbuilding. The protector should be grounded to the electrical service of the out building.
40 OSP Grounding & Bonding Issues: Recommendations for Fiber Optic Dielectric Cable or Dielectric Cable with a 26 AWG Trace WireBackground: RUS will publish their rules for grounding and bonding a 26 AWG trace wire in While the rules are not formal, they most likely will read in essence: “As per the requirement of the Engineer and in accordance with the NECS and NEC.”The NESC does not address the trace wire directly. By general description, a trace wire is considered a current carrying conductor.The plant side of a drop falls under the NESC.
41 OSP Grounding & Bonding Issues: Recommendations for Fiber Optic Dielectric Cable or Dielectric Cable with a 26 AWG Trace WireDielectric OSP cable does not have to be grounded.Per , you can isolate the trace wire instead of groundingDielectric OSP cable with 26 AWG Trace Wire should be grounded as follows:Only one end of the trace wire should be grounded.If both ends are grounded, it is a certainty that the trace wire will be destroyed due to lightening and it will be impossible to locate the cable.The Owner/Engineer should designate which pedestal the one end of the trace wire will be grounded (all even pedestals will be grounded, etc.)
42 Grounding Method Allowed ONT Grounding MatrixONT Location Matrix1/26/2012PreferenceDemarcation LocationONT TypeONT LocationDrop TypeGrounding Method Allowed1OutdoorIndoorFlat dropIsolate or ONTB2-5ArmoredONTB2--52ONTB2—53NoneAll45Notes:1: Outdoor cable can extend no more than 50' inside the building (Wall penetration, exit metallicconduit, or exit through concrete floor slab).2: Armored drop cable needs to be grounded in all cases due to lightning risk.3: When in doubt, ask.