Radio Antenna and Surge Arrester Grounding

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SEMN

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I am working on a wireless radio project. We are installing metal enclosures with wireless radios in them on the outside of buildings. Each radio has an associated antenna that will be mounted on a metal bracket on the outside of the building. LMR-400 cable is being run from the antenna to a surge arrester in the enclosure. The surge arrester is then connected to the radio. Each enclosure is powered by a 120VAC circuit from the building and is grounded back to the electrical panel board. Each surge arrester is grounded to a ground bar in the enclosure. I understand from 810 that the antenna mast and antenna discharge unit (surge arrester) must be grounded using to the grounding electrode. I presume this means that using the panel board ground is not adequate. I expect we will need a #10 copper wire to ground the antenna mast and another #10 to the enclosure ground bar for the surge arrester. My question is what to practically connect the other end of the #10 ground wires to. These are existing buildings and in most cases will not be near the electrical service entrance. I would think my best options would be the nearest metal water pipe, building steel accessible from inside the building, or finding other existing grounds like on to a roof top HVAC unit. Any practical suggestions on where to ground the grounding wire would be appreciated.
 
810.21 Bonding Conductors and Grounding Electrode Conductors — Receiving Stations. Bonding conductors or grounding electrode conductors shall comply with 810.21(A) through (K).
(A) Material. The bonding conductor or grounding electrode conductor shall be of copper, aluminum, copper-clad steel, bronze, or similar corrosion-resistant material. Aluminum or copper-clad aluminum bonding conductors or grounding electrode 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 conductors shall not be installed within 450 mm (18 in.) of the earth.
(B) Insulation. Insulation on bonding conductors or grounding electrode conductors shall not be required.
(C) Supports. The bonding conductors and grounding electrode 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.
Exception: Where proper support cannot be provided, the size of the bonding conductors and grounding electrode conductors shall be increased proportionately.
(D) Mechanical Protection. The bonding conductors and grounding electrode conductor shall be protected where exposed to physical damage. Where the bonding conductor or grounding electrode conductor is run in a metal raceway, both ends of the raceway shall be bonded to the contained conductor or to the same terminal or electrode to which the conductor is connected.
(E) Run in Straight Line. The bonding conductor or grounding electrode conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable.
(F) Electrode. The bonding conductor or grounding electrode conductor shall be connected as required in (F)(1) through (F)(3).
(1) In Buildings or Structures with an Intersystem Bonding Termination. If the building or structure served has an intersystem bonding termination as required by 250.94, the bonding conductor shall be connected to the intersystem bonding termination.
Informational Note: See Article 100 for the definition of Intersystem Bonding Termination.
​
(2) In Buildings or Structures with Grounding Means. If the building or structure served has no intersystem bonding termination, the bonding conductor or grounding electrode conductor shall be connected to the nearest accessible location on the following:

  1. The building or structure grounding electrode system as covered in 250.50
  2. 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
  3. The power service accessible means external to the building, as covered in 250.94
  4. The nonflexible metallic power service raceway
  5. The service equipment enclosure, or
  6. The grounding electrode conductor or the grounding electrode conductor metal enclosures of the power service
A bonding device intended to provide a termination point for the bonding conductor (intersystem bonding) shall not interfere with the opening of an equipment enclosure. A bonding device shall be mounted on non-removable parts. A bonding device shall not be mounted on a door or cover even if the door or cover is non-removable.
(3) In Buildings or Structures Without an Intersystem Bonding Termination or Grounding Means. If the building or structure served has no intersystem bonding termination or grounding means as described in 810.21(F)(2), the grounding electrode conductor shall be connected to an electrode as described in 250.52.
(G) Inside or Outside Building. The bonding conductor or grounding electrode conductor shall be permitted to be run either inside or outside the building.
70-684 (H) Size. The bonding conductor or grounding electrode 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 bonding conductor or grounding electrode conductor shall be permitted for both protective and operating purposes.
(J) Bonding of Electrodes. 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.
(K) Electrode Connection. Connections to grounding electrodes shall comply with 250.70.


 
Thanks for the reponse, but I was looking for more of an application answer than a simple copy and paste of the code I have already read.
 
Generally, the inspector has never really looked at tha so I'm not sure if what I ask for is "right"t, but I've asked the electricians to bond the conduits to the enclosures (the conduits that will contain the RF cables) to building steel. I think they also tend to continue it to a panelboard ground bar too because there could be other cables in there which require the metallic conduits be bonded (the last install had an SDS that needed building steel, so the same building steel was used for antennas and the SDS).

There must be some connection from the radio to inside the building. How do those wires get inside? Can you run a large wire that covers both GEC and bonding functions?
 
We are getting the 120VAC from inside the building. I would like to run a #10 ground to the electrical panel board power source, but I do not think that is acceptable per the code.
 
SEMN said:
We are getting the 120VAC from inside the building. I would like to run a #10 ground to the electrical panel board power source, but I do not think that is acceptable per the code.
Click to expand...
It is if the panelboard contains the building disconnecting means, and the point where the building grounding electrode system is bonded to the equipment grounding system. See 810.21(I).
 
SEMN said:
The antenna ground could only be connected to the panel board if the panel board was the main for the building, correct?
Click to expand...
Essentially... but the term "main" is subjective to individual interpretation. The panelboard would have to contain the building disconnecting means, which would be the service disconnecting means if supplied by a service. This is where the building grounding electrode system is connected to the equipment grounding system, or if a service, where the main bonding jumper is located.
 
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