TR41 01-05-009 (41.7.2 Costa Mesa – 607A specific_cmts) Letter Ballot T1 LB 945 Telcordia Comments January 19, 2000 Page 1 of 4 Comments to T1 Letter Ballot T1 LB 945 Draft Proposed American National Standard – Commercial Building Grounding (Earthing) and Bonding Requirements For Telecommunications Technical Comments 1. Clause 3.2, Definition of terms. Delete the definition of coupled bonding conductor (see technical comment 4). If the consensus is not to delete, replace the existing definition as follows: “Coupled bonding conductor: A conductor used with and tie-wrapped to the exterior of UTP cable to extend the Telecommunications Main Grounding Busbar (TMGB) in the telecommunications Entrance Facility (TEF) to certain types of ac-powered terminal equipment. It is intended to minimize, through mutual coupling with UTP cable conductors, lightning-introduced surge voltages between the equipment and its local ground.” Rationale: The coupled bonding conductor was introduced many years ago to address a specific lightning susceptibility situation associated with certain ac-powered equipment. The coupled bonding conductor is little used, if at all, in today’s installations and should be eliminated from this document. If it is not removed, then the definition should be revised to address the specific function of the coupled bonding conductor. The existing definition provides a very general description, applicable to any bonding conductor, and does not address the true function and purpose of the coupled bonding conductor. 2. Clause 22.214.171.124. Revise as follows: “126.96.36.199 Each telecommunications bonding conductor The bonding conductor for telecommunications, each telecommunications bonding backbone (TBB) conductor, and each grounding equalizer (GE) shall be green or marked with a distinctive green color. Rationale: The present text, as contained in the proposed draft standard, requires all grounding and bonding conductors to be “green”. This could be interpreted as applying to the primary and secondary protector bonding/grounding conductor, and is not required by the NEC. Left unchanged, clause 188.8.131.52 requirements would exceed NEC requirements without demonstrated safety or administrative justification. 3. Clause 184.108.40.206. Revise as follows: “The metallic cable shield shall not be permitted to be used as a TBB.” Rationale: Telco practices have long permitted the use of the cable shield as a grounding conductor. Practices call for cable shield continuity to be maintained and for the cable shield to be grounded at each floor where pairs are broken out. If the use of the cable shield is disallowed, there will be a great number of commercial buildings that are not in conformance with the proposed 607-A standard. 4. Clause 220.127.116.11. Delete the note regarding the coupled bonding conductor. Rationale: See technical comment 1 and the accompanying rationale. TR41 01-05-009 (41.7.2 Costa Mesa – 607A specific_cmts) Letter Ballot T1 LB 945 Telcordia Comments January 19, 2000 Page 2 of 4 5. Clause 18.104.22.168. Revise as follows: “22.214.171.124 The TBB within the same space shall be bonded to the TGB using a conductor sized as specified in 126.96.36.199. Bonding to other TGBs in the same space shall be accomplished using a minimum No. 6 AWG conductor.” Rationale: The present wording requires, for a TBB sized at 3/0, all bonding conductors between the TBB and TGB, and between TGBs in the same space to also be 3/0. This is an unnecessarily large conductor and is difficult to place and secure. Telecom experience has shown that a No. 6 AWG bonding conductor is adequate for bonding within commercial buildings. It is reasonable to size the TBB-to-TGB bonding conductor equal to the TBB as it will be required to carry the sum of all fault currents from multiple TGBs. Individual TGB fault currents are not likely to be as large. Recall that we have made the assumption that there are multiple paths for the fault current (see 188.8.131.52, last sentence). We also use No. 6 AWG to bond to building steel which is another fault current path (see 5.6.3). 6. Clause 7.2, second sentence. Revise as follows: “… bonded together with a conductor sized per 184.108.40.206 using a minimum No. 6 AWG conductor or splice bars.” Rationale: See rationale for technical comment 5. 7. Annex C. Globally change “solid, bare tinned-copper (SBTC) conductor” to “solid, bare copper (SBC) conductor”. Rationale: Most telco practices do not call for tinned copper conductors. Acceptable results have been obtained without requiring tinned conductors. 8. Annex C, clause C.4.3. Add as second sentence: “Ground rods should be copper clad, stainless steel, or zinc clad.” Rationale: If the document is going to cover tower grounding and prescribe the use of ground rods, it should also suggest the type (material) of ground rods that are acceptable. 9. Annex C, clause C.9.2. Revise “760 mm (30 in)” to “380 mm (18 in)”. Rationale: Consistency with the depth of burial requirements specified for the ground ring. 10. Annex C, clause C.9.3. Delete the sentence: “Wire lengths of up to 500 feet (152 m) might be required.” Rationale: The inclusion of this sentence encourages the reader (engineer) to specify unnecessarily lengthy radial conductors, at increased cost, without demonstrated need or improvement in contact resistance. The previous sentence directing the reader to “… extend each radial wire as far as necessary to obtain the desired resistance” is sufficient. 11. Annex D, Figure D.2-1. Revise the text associated with the arrow pointing to the qudraplex ac outlet as follows: “External secondary protector unit surge protective device (SPD)”. Rationale: The term “secondary protector unit” refers to a telecom protector. The application being referred to here is an ac branch circuit and “surge protective device” is the proper term. 12. Annex D, Figure D.2-1. In the telecom room, show a bonding conductor between the chassis of the channel equipment and the TGB. Rationale: Correlation with Figure 1 of T1.321 and required bonding for effective voltage equalization at the work station. TR41 01-05-009 (41.7.2 Costa Mesa – 607A specific_cmts) Letter Ballot T1 LB 945 Telcordia Comments January 19, 2000 Page 3 of 4 13. Annex D, Figure D.2-1. In the telecom room, revise “channel eqpt.” to “voice and data channel eqpt.” Rationale: Correlation with Figure 1 of T1.321 and need to indicate that for protection at work stations to be effective, voice circuits must be bonded as well. 14. Annex D, Figure D.2-1. Indicate the duplex outlet as the “Branch circuit outlet box”. Show a bonding conductor between the position bonding terminal and the branch circuit outlet box. Rationale: Correlation with Figure 1 of T1.321; all “services” must be bonded at the work station for effective voltage equalization. 15. Annex D, Figure D.2-1. Indicate “ACEG provided in AC supply cords” for power cord to qudraplex outlet, and power cords to the video display and processor/controller. Rationale: Correlation with Figure 1 of T1.321; all “services” must be bonded at the work station for effective voltage equalization. 16. Annex D, Figure D.2-1. Indicate the bonding conductor between the qudraplex ac outlet and the “external secondary protector unit” as a heavy bold line, as are other bonding conductors. Rationale: Correlation with Figure 1 of T1.321; all work position bonding conductors should be “bold” for emphasis as they are necessary for effective voltage equalization. Editorial Comments 1. Revise “Foreword”, “contributing organizations”, second sentence as follows: “… Considerations Technical Subcommittee TR41.7, and Tthe Alliance for …”. 2. Revise “Foreword”, “Documents Superceded”, fourth bullet to include the symbol as follows: “National Electrical Code (NEC)”. Both are registered trademarks of NFPA. Remove symbol from subsequent appearances; it only needs to be shown at first appearance. 3. Revise Clause 1.1.1, fourth sentence to include the word “infrastructure” as follows: “… building grounding and bonding infrastructure is frequently placed during …”. 4. Revise Clause 1.8.2, third sentence to indicate that update recommendations should be sent “… to the Telecommunications Industry Association at the address indicated in the Foreword”. Since this is a joint revision by T1E1 and TR41, and multiple chairs are indicated in the Foreword, this clause as presently stated could be very confusing to the reader. Also, at this point in time, TIA will be the “keeper” of this standard. 5. Combine clauses 2.1.2 and 2.1.3 into a single clause 2.1.2 as follows: “This Standard specifies the framework for the telecommunications grounding and bonding infrastructure, and its interconnection to other building systems. Figure 2.1-1 depicts …”. Renumber clauses 2.1.4, 2.1.5 and 2.1.6 as 2.1.3, 2.1.4, and 2.1.5, respectively. Combining the two clauses presents the purpose of the infrastructure in a single, concise sentence. 6. Clause 2.1.3, second bullet. Add “the” before “telecommunications”, or make “room” plural. 7. Figure 2.1-1. Revise “Telecommunications Grounding Bar” to “Telecommunications Grounding Busbar”. TR41 01-05-009 (41.7.2 Costa Mesa – 607A specific_cmts) Letter Ballot T1 LB 945 Telcordia Comments January 19, 2000 Page 4 of 4 In the telecom entrance facility, correct typo for “Bonding conductor for telecommunications”. Ditto for Figures 2.1-2, 5.3-1. 8. Clause 3.4, the symbol for ohms should be omega (), not the symbol that is indicated. 9. Section 5.1. Globally replace “bonding conductors” with “grounding and bonding conductors” for consistency with section title and clauses 5.1.1 and 5.1.2 10. Clause 5.1.3, second sentence. Add NRTL as follows: “… listed by a nationally recognized testing laboratory (NRTL) for …” for consistency with clause 5.1.2, and to eliminate confusion sometimes caused by the use of the word “listed” by itself without any explanation. 11. Clause 5.1.4, second sentence. Revise as follows: “… each end of the conduit with using a grounding bushing or a No. 6 AWG …”. 12. Clause 5.2.1, second sentence. Revise as follows: “… attachment point for the telecommunications bonding …”. 13. Figure 5.2-1. Revise title to state: “Typical telecommunications main grounding busbar (TMGB).” This proposed change will be consistent with the text of clause 220.127.116.11 and the titleof Figure 5.5-1. It will also indicate that the figure is for guidance and not expected to be exactly replicated. 14. Clause 18.104.22.168. Revise the word “panelboards” to “panelboard’s”. Ditto for clause 22.214.171.124. 15. Clause 126.96.36.199, first sentence. Revise as follows: “Connections of the TBB and the GE to the TGB shall …”. 16. Clause 6.2.1, second sentence. Change “This” to “The”. 17. Clause 7.4.2, first sentence. Revise as follows: “… as the TGB shall be bonded to the TGB.” 18. Annex A. Add “Approved floor ground” to other industry terms for TGB. This is a term widely used in telco practices. 19. Annex C, clause C.5.3.1. Change “must” to “should” as this annex is informative. 20. Annex C, clause C.6.1. Revise as follows: “… mounted on the roof of a building, design a grounding system should be designed that: …” as this annex is informative. 21. Annex C, clause C.8.1. Revise as follows: “Support r Roof conductors should be supported every 1 m …” as this annex is informative. 22. Annex C, Clause C.9.1. Revise as follows: “Provide r Radials should be provided if ground rods …”. “When radial grounding ….. necessary, use the following should be used to determine requirements” as this annex is informative. 23. Annex C, clause C9.1.1 Delete the word “provide” and revise to state: “… to the ground rings should be provided.” as this annex is informative. 24. Annex C, clause C.9.2. Replace the word “use” with “a”; add “should be used” to the end of the sentence as this annex is informative. 25. Globally replace the word “telecommunication” with the word “telecommunications” for consistency throughout the document.