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    Communication systems & strikes

    I have seen drawings showing a transient connection on ground between rods of communication system and rods of lightning ps, i know it's not required by code but the designer justified his design to disallow the return of lightning discharge, i said that we use the spd devices in all emergency panels per code including the communication, his justification which makes sense that grounding busbar in communication rooms are bonded together and go to ground, the equipment in communication room are bonded to busbar and go to rods belong to communication system accordingly there is no spd to disconnect the connection during strike unless we have a transient connection connected on ground,
    If he is right, why nec doesn't require?
    "Sleem"

    #2
    Originally posted by m sleem View Post
    I have seen drawings showing a transient connection on ground between rods of communication system and rods of lightning ps, i know it's not required by code but the designer justified his design to disallow the return of lightning discharge, i said that we use the spd devices in all emergency panels per code including the communication, his justification which makes sense that grounding busbar in communication rooms are bonded together and go to ground, the equipment in communication room are bonded to busbar and go to rods belong to communication system accordingly there is no spd to disconnect the connection during strike unless we have a transient connection connected on ground,
    If he is right, why nec doesn't require?
    That is a design issue. The NEC is not a design manual. You can find more detailed information from Motorola's R56 grounding guide lines.
    Organized people are people that are just too lazy to look for their stuff

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      #3
      Originally posted by ceb58 View Post
      That is a design issue. The NEC is not a design manual. You can find more detailed information from Motorola's R56 grounding guide lines.
      IMHO, it's not a design issue, the NEC requirements shall provide a complete protection for building occupancies and equipment and even structure, but in this case the body of communication equipment is not fully protected during lightning strike.
      "Sleem"

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        #4
        Nope. NEC requirements are not a complete lightning protection system. See NPFA 780, or the Motorola guide mentioned above.

        Comment


          #5
          Originally posted by m sleem View Post
          IMHO, it's not a design issue, the NEC requirements shall provide a complete protection for building occupancies and equipment and even structure, but in this case the body of communication equipment is not fully protected during lightning strike.
          In what the OP describes is a standard grounding set up for a communication tower. Every thing is bonded together to keep every thing at the same potential in the event of a strike. You can have all the SPD on the panels you want but you want nothing to break the bonding connections. All equipment, panels, racks, fence and tower legs are all bonded together with one grounding system. We always joked at our tower sites that if you stood still for 5 min. someone would come by and connect a bond wire to you.
          Organized people are people that are just too lazy to look for their stuff

          Comment


            #6
            Originally posted by ceb58 View Post
            We always joked at our tower sites that if you stood still for 5 min. someone would come by and connect a bond wire to you.
            our running gag was "if it don't move bond it......"
            Sometimes I don't know whether I'm the boxer or the bag.

            Comment


              #7
              Originally posted by ceb58 View Post
              In what the OP describes is a standard grounding set up for a communication tower. Every thing is bonded together to keep every thing at the same potential in the event of a strike. You can have all the SPD on the panels you want but you want nothing to break the bonding connections. All equipment, panels, racks, fence and tower legs are all bonded together with one grounding system. We always joked at our tower sites that if you stood still for 5 min. someone would come by and connect a bond wire to you.
              So, how you protect equipment bodies from damage due to the return path of lightning strikes?
              "Sleem"

              Comment


                #8
                Originally posted by ceb58 View Post
                In what the OP describes is a standard grounding set up for a communication tower. Every thing is bonded together to keep every thing at the same potential in the event of a strike. You can have all the SPD on the panels you want but you want nothing to break the bonding connections. All equipment, panels, racks, fence and tower legs are all bonded together with one grounding system. We always joked at our tower sites that if you stood still for 5 min. someone would come by and connect a bond wire to you.
                Exactly correct on single point ground!
                Moderator-Washington State
                Ancora Imparo

                Comment


                  #9
                  Originally posted by m sleem View Post
                  So, how you protect equipment bodies from damage due to the return path of lightning strikes?
                  Not sure what you are referring to
                  "equipment bodies"
                  "return path"
                  The initial leader for lighting is from ground to cloud and then the big strike is cloud to earth
                  Moderator-Washington State
                  Ancora Imparo

                  Comment


                    #10
                    This is what i want to explain, the return of the strike would go to telecom equipments in case of bonded together,
                    Am i missing something?
                    "Sleem"

                    Comment


                      #11
                      Technology grounding standard

                      Originally posted by m sleem View Post
                      I have seen drawings showing a transient connection on ground between rods of communication system and rods of lightning ps, i know it's not required by code but the designer justified his design to disallow the return of lightning discharge, i said that we use the spd devices in all emergency panels per code including the communication, his justification which makes sense that grounding busbar in communication rooms are bonded together and go to ground, the equipment in communication room are bonded to busbar and go to rods belong to communication system accordingly there is no spd to disconnect the connection during strike unless we have a transient connection connected on ground,
                      If he is right, why nec doesn't require?
                      The current grounding standard for technology is ANSI/TIA-607-C and is very detailed towards deign installation and testing requirements.
                      • TIA-607 recommends a 6-awg bond between the power panel (providing power to the TR) ground bus and the Telecom Room (TR) busbar kit.
                      • TIA-607 also recommends 6-awg bond to building steel but only where the building steel is not to be used as a lightning arrestor down-conductor. When building steel is used as a down conductor the recommendation is to provide separation (not attach).
                      • There should be a separate telecom ground riser backbone that is bonded to building service entrance ground bus at only (1) point and otherwise isolated.

                      There are also NEC code references to incorporate.
                      • 2017 NEC 800-53 requires 6' separation of communication cables to lightning arrestor down-conductors where practicable
                      • NFPA 780 contains additional information on lightning arrestor system design.

                      Comment


                        #12
                        Originally posted by m sleem View Post
                        This is what i want to explain, the return of the strike would go to telecom equipments in case of bonded together,
                        Am i missing something?
                        The lightning current has no particular desire to go to the server room. It might go there because it is inclined to go everywhere it can. It might, or might not, send much more current through the underground bonding wire than it would through the earth. After all, if that underground wire is bare copper as it should be, then the strike can discharge to the earth all along the route. To my understanding there isn't too much certainty about predicting exactly which way lightning will go.

                        One thing that strikes me as relatively certain though, is that if you don't bond the grounding systems with a 6awg wire at ground level, and the lightning finds some other unanticipated path through other wires above ground, it would do a lot more damage along that path than along a 6awg copper wire in the ground.

                        Finally, I believe the NEC requires the lightning system to be bonded to the premises grounding system so that in case the lightning system were to somehow be accidentally energized by a human-made source it would trip a breaker. Same principle as bonding water pipes and gas pipes. The imperatives of protecting people from human-made shocks and protecting against lightning damage do not dovetail well at all, to my understanding. Add to this a certain amount of grounding religion in some people's heads, and it may be quixotic to think all of the various codes and standards will make any kind of unifying sense.

                        Comment


                          #13
                          Again, Motorola R56 is the standard for telecom and cell towers. The cell companies use a single point ground....lightning wants to go to a earth ground, path to the equipment is high impedance.
                          Moderator-Washington State
                          Ancora Imparo

                          Comment


                            #14
                            Originally posted by tom baker View Post
                            Again, Motorola R56 is the standard for telecom and cell towers. The cell companies use a single point ground....lightning wants to go to a earth ground, path to the equipment is high impedance.
                            Equipment's body is metal, how earth has lower impedance?
                            "Sleem"

                            Comment


                              #15
                              Originally posted by m sleem View Post
                              Equipment's body is metal, how earth has lower impedance?
                              The earth is a much, much larger conductor.

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