Antenna mast grounding question - Page 2 - AVS Forum
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post #31 of 39 Old 06-19-2013, 10:31 AM
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Originally Posted by Keizer View Post

In my county we have to pound in two 6' ground rods and attach them with #6 copper wire, then connect to the ground bar in the sub panel. I think they do this because of all the rocks that are in the soil and they know you would never get an 8' ground rod all the way in the ground. With two 6' rods, you have a better chance of getting enough rod into the ground.
All the raceways on my panels are plastic electrical conduit.

There are other regions with rock problems more severe than yours where they allow use of an 18" square ground plate instead of a ground rod for the formation of the ground electrode system.

I seriously doubt that your local code explicitly states that the ground rod used to satisfy section 810 of the code for grounding an antenna mast can be connected to a ground bar in a subpanel.

FWIW, if you do further explore local variations of permissible ground bonding practices, be aware that there is a difference between a supplemental ground rod and a supplementary ground rod. One is the rod used to develop a conforming ground electrode system, whereas the other is an auxiliary rod installed near a grounded component or device to develop a shorter, straighter ground path for lightning. I'll have to Google to refresh my recollection regarding which is which, but the specifications of those auxiliary ground rods are not governed by ground rod specifications in the 250s sections. Last I knew, section 800, for telephone wiring, permitted the use of a five foot rod, and other sections did not mandate or specify the particulars on auxiliary rods that might be used at the installer's discretion. Radio Shack used to stock four foot ground rods. While you won't often read me sticking up for Radio Shack, it seems likely that they must have been advised somewhere along the line that there were situations in which such rods were permissible under the NEC, but those uses did not include the formation of the ground electrode or the auxiliary grounding of masts under section 810 or communications wiring under 800. It could well be that a person could have driven drive a four foot, bonded rod to satisfy the prior section 820 language of the late 1990s and early 2000s code editions, but I don't have any of those available for scrutiny at present. Beyond that, I'm only vaguely away of the details of the 2008 revision (of which i have a copy) that now intertwine sections 810 and 820.
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post #32 of 39 Old 06-19-2013, 10:47 AM - Thread Starter
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Originally Posted by AntAltMike View Post



I seriously doubt that your local code explicitly states that the ground rod used to satisfy section 810 of the code for grounding an antenna mast can be connected to a ground bar in a subpanel.

Sorry, I wasn't being very clear. When I mentioned that we had to drive two 6' ground rods, this had nothing to do with antenna grounding. Anywhere you add a sub panel, you have to ground the panel with two 6' ground rods. At my pump house....two ground rods. At my 200 amp service panel.....two ground rods. At my house sub panel......two more ground rods, etc.
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post #33 of 39 Old 06-19-2013, 10:51 AM - Thread Starter
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I seriously doubt that your local code explicitly states that the ground rod used to satisfy section 810 of the code for grounding an antenna mast can be connected to a ground bar in a subpanel.

If I connect the antenna mast ground wire to one of the two existing ground rods outside my garage, it will basically be connected to a ground bar in the subpanel. Those two ground rods out there are connected to each other with #6 copper wire, and are then connected to the ground bar in the panel.
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post #34 of 39 Old 06-19-2013, 11:09 AM
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Originally Posted by Keizer View Post

If I connect the antenna mast ground wire to one of the two existing ground rods outside my garage, it will basically be connected to a ground bar in the subpanel. Those two ground rods out there are connected to each other with #6 copper wire, and are then connected to the ground bar in the panel.

No matter where you attach to ground, it is electrically connected to every ground point in the system, but if you run a ground wire yourself to the ground bar, you will be making a violation that stands out like a sore thumb. I once grounded to a screw on an exterior faucet that I knew was just screwed into plastic, but no one else knew.

I would imagine that your subpanel has to be bonded to the ground electrode system, so then at least one of those two ground rods has to be part of the ground electrode system and you can connect to that. Upon rereading your previous post, it looks like your local code allows sub panels in detached buildings to be excused from the commonplace subpanel bonding requirement.

You will have to use a separate, dedicated ground rod attachment "acorn" to connect your ground wire to either rod.
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post #35 of 39 Old 06-19-2013, 05:22 PM - Thread Starter
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Originally Posted by AntAltMike View Post


You will have to use a separate, dedicated ground rod attachment "acorn" to connect your ground wire to either rod.

Okay, got some #10 copper wire and a ground rod acorn at the Depot this afternoon. Out of curiosity, why do I have to use a separate, dedicated ground rod attachment acorn? Why can't I just loosen the existing clamp on the ground rod that's holding the #6 wire to the garage sub panel? Then stick the #10 wire in there with it?
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post #36 of 39 Old 06-19-2013, 07:48 PM
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Why can't I just loosen the existing clamp on the ground rod that's holding the #6 wire to the garage sub panel? Then stick the #10 wire in there with it?

Because that would be a code violation unless the clamp were specifically listed for multiple conductors. [250.70 NEC 2011]

Seriously, use the split bolt and nut on the #6 cable ground electrode conductor between the panel and its grounding rods. It's straightforward and, best of all, it's a permitted means of connection [810.21(F)(2)(6) NEC 2011]
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post #37 of 39 Old 06-20-2013, 07:11 PM
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Originally Posted by Wendell R. Breland View Post

...IIRC, NEC states there are to be no splices in the ground wire between the mast and ground electrode.

While I've seen that same claim made over a dozen times in grounding threads, no one has ever accompanied such a claim with a NEC section citation. And a few forum contributors, including at least one licensed electrician, have insisted that if you use insulated grounding wire, the insulation has to be green, which I never do because black is found less objectionable by many customers, but I've never seen an NEC citation in support of that, either.

It is possible that there are requirements that the ground wire be continuous and that insulated ground wires be green in other sections where the safety concerns are greater, like it could be that the ground wire that bonds the service entrance (meter), the service panel (primary breaker) and the ground electrodes together has to be continuous, and it could well be that ground wire used to ground the third conductor of a 110 volt plug has to have green insulation, when insulated, because of the magnitude of the risks that can occur if those grounds fail or are misconnected, but like the 250 section ground rod specifications, which do not apply to all ground rods, there may be explicit stipulations and prohibitions on splicing and insulation color that only apply to the section or subsection of the code in which they appear.

There is a UL listed product called a split bolt that seems to exist just for the purpose of splicing ground wires. Here is a description of them from Allied Bolt Inc's catalog:

FUNCTION
Quote:
Split Bolts are used to mechanically bond copper wires of various sizes. Allied’s Split Bolts are approved for use in grounding, bonding, electrical and direct burial applications.

Yet there are split bolts that are too small to couple a mast ground wire or an outer conductor wire with even the smallest (6 gauge) permissible bonding conductor, so if ground wires have to be continuous, of what use could they possibly be?

ASKA SB-8 Split Bolt UL-Listed DNA



ASK1005
Quote:
Description
Model SB-8UL Split bolt is UL-listed and Dish Approved.
#8 wire


Quote:
I would also use my own ground wire clamp (available at Home Depot, Lowe's, Ace, etc.) to the ground electrode.



Back when DISH Network used to give a "free" (Value: $79.99) installation kit with each system it sold, they used to include 25 feet of 8 gauge aluminum ground wire and so, when a residential customer copped out on the self installation and pawned it off onto me, I used to use the zinc plated version of the style clamp shown above to interface the aluminum ground wire with the copper water pipe. I don't know for sure if it is permissible to use a zinc plated clamp to attach an aluminum wire. Does anyone here know?
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post #38 of 39 Old 06-21-2013, 08:40 AM
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Originally Posted by AntAltMike View Post

While I've seen

Just a case of not the best answer to a specific question on my part, it should have been "do not connect to the bus bar". ProjectSHO89 did a better job than I by pointing out that connection to the bus bar is not permitted.


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post #39 of 39 Old 06-09-2014, 11:35 AM
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Originally Posted by holl_ands View Post

There is a paragraph (sec 820.3) referencing different requirements sections for antennas larger and less than 1 meter (39.37 inches) in diameter. However the requirement to ground antenna masts is found in the earlier sec 810, which MAY OR MAY NOT apply to ALL size OTA Antennas....it's AMBIGUOUS. BTW: I also looked at EVERY occurrence of "antenna" and "mast" throughout the document. Writing, reviewing and testing conformance to Technical Specifications used to be a big part of my job as a Comm Engineer, so I developed an eye for spotting and avoiding ambiguities.

From 2014 NEC Draft:

Article 810 Radio and Television Equipment:

Sec 810.1 SCOPE: ".....This article covers antennas such as wire-strung type, multi-element, vertical rod, flat, or PARABOLIC exceeding 1 m (39.37 in.) in diameter or across and also covers the wiring and cabling that connects them to equipment....." [AMBIGUOUS....it could exclude ALL Antennas or ONLY PARABOLIC antennas less than 1 m in diameter.]

Sec 810.3 Other Articles: "....For antennas exceeding 1 m (39.37 in.) in diameter or across coaxial cables that connect antennas to equipment shall comply with Article 820. For antennas 1 m (39.37 in.) or less in diameter or across, coaxial cables that connect antennas to equipment shall comply with Article 840....." [Note that this section did NOT limit to PARABOLIC ONLY.]

[So PARABOLIC and maybe ALL outdoor antennas less than 1 meter diameter are EXEMPT from following Sec 810.15 requirements:]

Sec 810.15 "Grounding. Masts and metal structures supporting antennas shall be grounded in accordance with 810.21."

Sec 810.21 "Bonding Conductors and Grounding Electrode Conductors — Receiving Stations. Bonding conductors and grounding electrode conductors shall comply with 810.21(A) through (K)."
"(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."

Sec 820 CATV Systems: The usual ground and bonding requirements for Cable Networks. [Don't be mislead by the term: CATV = Community Antenna TV Network...clearly this does not apply to OTA and SAT Dish systems.]

Sec 840 Premises-Powered Broad-Band Communications Systems: ...."that provide any combination of voice, video, data, and interactive services....such as fibre optic and PARABOLIC antenna systems....includes Premises-Powered CATV wiring network [i.e. interior wiring & equipments]".

840.93 Grounding or Interruption. "Non–current-carrying metallic members of optical fiber cables, communications cables or coaxial cables entering buildings or attaching to buildings shall comply with 840.93(A), (B) or (C), respectively." "(B) Communications Cables. The grounding or interruption of the metallic sheath of communications cable shall comply with 800.93."

800.93 Grounding or Interruption of Metallic Sheath Members of Communications Cables. "Communications cables entering the building or terminating on the outside of the building shall comply with 800.93(A) or (B)." [ONLY discusses grounding of the cable shield....no mention of antennas or antenna masts.]

OTA Antennas and Sat Dishes still have to use a grounding block and associated grounding connection. In Sec 810.1 Scope, it appears that Direct Broadcast Systems (DirecTV, Dishnet, et.al.) were granted an exemption from grounding the actual PARABOLIC (if less than 1 meter diameter)....but this section COULD be (mis?) interpreted to also exempt small OTA antennas (it's AMBIGUOUS), by being EXCLUDED from the subsequent Sec 810.15 & 810.21 requirements to ground the "Masts and metal structures supporting antennas".


this thread is about a year old....just wondering if anyone found out for sure if small antennas like the rca ant751 are exempt from ground requirements under the new nec guidelines? thanks
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