Direcciones IPv6 Unicast

4.4.1.1 The practices required here are the same as indicated above, with the exception of the following. Because the tenant’s coax cable grounding sheaths are bonded to the tower, their grounding system must be connected into our system via the buried ground ring around the tower. This should have the overall effect of lowering the system ground resistance reading. In cases where we have other tenants install their equipment on our towers and/or sites, commonly referred to as a co-location, the following is to be implemented.

4.4.1.2 When a tenant on a tower wants to connect to the existing grounding system, that connection should occur on the tower buried ground ring only and not on our building ground ring.

4.4.1.3 When a tenant on a tower connects their grounding system into our tower ground, it is important that an inspection sleeve be installed where the actual exothermic weld occurs on our tower buried ground ring. This will allow for verification of the weld and provides a fixed monitoring point for inspection purposes.

4.4.1.4 Once the connection to the tower buried ground ring has been completed, a visual inspection is to be done, prior to the ring being covered with earth. This again will serve as a means of verifying the quality of the installation.

Figure 4-3

Typical Co-Locate Cell Site Grounding Detail

4.4.2

4.4.2.1 The general requirements for a driven ground system at a radio/cell site are the same as those for a MSC. They apply to radio sites as well as MSC’s that contain switching and radio equipment.

4.4.2.2 Each ground rod of a driven system and every service ground rods or buried objects in the vicinity of a building that may act as unintentional electrodes, shall be bonded to the buried ground ring to limit potential differences between them.

4.4.2.3 The buried ground ring shall be bonded to tower legs, exterior buried and above surface metallic objects, other electrodes, and to the interior ground ring and antenna cable exterior hatch-plate ground bars.

4.4.2.4 Unit bonds connected to the buried ground ring shall be No. 2 AWG bare tinned solid copper wire. Connections to the ring shall be exothermically welded by technicians certified on the process. Connections to above ground units shall be made with exothermic weld, where practical, or with 2 hole connectors. Two-hole brass connectors with stainless steel hardware, with 2 set screws are preferred. 2 hole crimp connections may be used with a double hydraulic crimp connection. Hydraulic compression connections such as “Burndy HyGround” may be used in an exterior application for conductor to conductor connections below grade where exothermic welds are not practical and on a rooftop sites where exothermic welds may be a fire hazard. Connections other than exothermic weld shall be located so as to facilitate periodic inspection and maintenance.

4.4.2.5 All buried connections shall be exothermic welds. All mechanical connections shall be treated with a protective, anti-oxidant coating. All exothermic welds to galvanizing surfaces shall be sprayed with galvanizing paint.

4.4.2.6 Bonds to the buried ground ring are categorized as follows: Buried metallic objects:

Driven ground rods

Power company or other driven electrodes

Fuel tanks, unless protected with cathodic system utilizing sacrificial anode rods. Conduits, pipes

Other objects with metallic connection to the building (potential earth electrodes).

Earth supported metallic objects located within, or less than 6 feet from the perimeter of the buried ground ring:

Tower legs, preferably 12 inches above the pad, via PVC pipe through the pad, in order to avoid sharp bends. Exothermically welded

connections are recommended. Mechanical connections at tower

legs are acceptable only if structural concerns exist or when specifically recommended by the tower manufacturer. A flange or pigtail welded at the factory is desirable to avoid destroying the interior galvanizing during the exothermic welding process. For a metallic monopole, two such bonds shall be made to the base on opposite sides. Specific design considerations, in addition to the above, may be required when using concrete monopoles.

Metal fence posts within 6 feet of the buried ground ring shall be bonded at 25 foot intervals if run continuously. Gate fence posts shall be bonded to the buried ground ring. Provide flexible copper strap exothermically

welded to the gate fence post and gate.

Refer to the Monopole Grounding and Buried Monopole Grounding Details below.

Figure 4-4

Monopole Grounding Detail

Other metallic objects of significant size.

Tower exit ground bar shall be exothermically connected to No. 2 tinned solid copper at lowest point of bar and connected to the buried ground ring (welded to conductor).

Each ice bridge leg shall be bonded to the buried ground ring with No. 2 AWG bare tinned copper conductor. Provide exothermic weld at both the ice bridge leg and buried ground ring.

each tower leg. (E.g. two connections per caisson.)

Figure 4-5

Buried Monopole Grounding Detail

Metallic objects mounted on the building: Ground bars at the cable entry port. Down spouts or metal drains.

Aluminum (or similar) exterior wall siding (with a bi-metallic connector).

Conduits, pipes (multiple grounds required every 25 feet when run is parallel to earth on exterior walls).

Air exhausts hoods.

Parapets (at each corner of the building when parapets are electrically continuous, otherwise at least one bond to each discontinuity in addition to the corners).

Metallic structures supported on the roof.

Exterior Surge Suppressors associated with AC service.

Outer sheath of co-axial antenna cables (via cable entry port ground bar). Metallic doors and frames.

Utility company meter housing. Main disconnect switch.

Air conditioning units and associated disconnect switch. Generator receptacle.

Conduit routed near the cable entry port, shall be bonded to the exterior cable entry port ground bar and, if the conduit run is underground before entering the building, it shall be bonded to the exterior buried ground ring. The conduit shall also be bonded to the interior ground ring upon entry into the equipment area. Conduit shall not be exothermically welded.

Other metal of similar nature.

These connections to the external ground ring are not in lieu of the NEC green wire equipment ground to the AC panel-board.

Metallic components of the building structure:

Steel members in foundation walls (e.g., bond each building perimeter column).

Outer layer of reinforcing bars in exterior walls of reinforced concrete buildings (e.g., one bond per area between adjacent columns of 25 foot intervals, maximum).

Reinforcing bars of concrete knockout panels (rebars not in contact with building structure rebars). Other building structure metal exposed on outer surface of building.

A large variety of metallic objects external to or mounted on the building shall be bonded to the exterior buried ground ring to ensure equalization of potential.

4.4.3

4.4.3.1 Each guy wire shall be grounded at the anchor point. A ground ring conductor and at least 2 ground rods shall be installed at each guy anchor and a No. 2 AWG tinned solid copper wire shall be connected to the buried ground ring system from each of the guy wires. Cable clamps shall be used so that direct contact between copper and the guy cable is avoided. Provide a No. 2 AWG tinned solid copper jumper across the turnbuckle of the lowest guy cable. See Figure 4.6.