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I'm mounting a light-weight metal TV antenna to a metal mast attached to old-school metal roof columns (with the curly-cues) on a small second floor porch which has a metal porch roof, and metal floor covered with outdoor deck carpet. The mast mounts have rubber bumpers between them and the metal porch supports. The mast does not touch the porch floor, so there does not appear to be a bond (?) between the antenna and metal porch components. The mast extends a few feet above the porch, but nowhere near the height of the brick house, which has a gable roof going at least another 10 feet higher.

The mast and coaxial are each grounded to the house ground rod with 10 gauge wire. The 1930's house has one primary rod of unknown/unmarked length near a newer 200amp box, and the cable/internet service line grounds to a 5' rod 30' away from the primary rod. I have bonded the 5' cable rod to the primary rod with #6. The unused phone line-in is grounded to the iron water line-in (which goes at least 40' underground to the meter at the street). The main panel is near the water-in, but not grounded to it. Presumably the primary rod, even with the cable rod, isn't 'code' (no ohm test). I know one option is replace the unknown primary with two 8' rods > 6' apart, bonded by #6. I'm not inclined to bother with the aging iron pipe. Input about the grounding electrodes is welcome, but I'm inclined to do two new 8' rods and a jumper. So...

  1. If I replace the unknown rod with 8', and replace the 5' cable rod with 8', and bond them using the existing #6 jumper (30' length), is that ok, even if something is grounded to each rod (electric to one, cable to other)?

  2. Should I ground the metal porch to the rods (or perhaps to the grounded antenna mast, which is grounded to the rods)?

  3. If I leave the phone line grounded to the water pipe, does the pipe need to be bonded to the ground rod (my understanding is that grounding electrodes are supposed to be bonded together)?

  4. Am I correct to bond the cable ground rod to the main rod? Was it unnecessary?

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Two many questions so I will tackle a few code issues. The water pipe is required to be bonded to your electrical system so go ahead and use it as a second electrode. In truth that water pipe is normally a much better electrode than a standard 8’ ground rod.

I might drop a 2nd 8’ at 6’ or more away from your existing unknown rod. Many people here probably have not heard of a 5’ communications ground rod but it is normally allowed when the service panel and grounding electrode system is further than 20’ NEC 800.100.a.3 & 800.100.B.3.2

Section 800 is a stand alone section and is not subject to all the rules of chapters 1-7 as specified in 90.3

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You were correct to bond the rods to each other

As per NEC 820.100(D), a CATV grounding rod shall be bonded to the house grounding electrode system with no smaller than a #6 copper wire:

(D) Bonding of Electrodes. A bonding jumper not smaller than 6 AWG copper or equivalent shall be connected between the community antenna television system's grounding electrode and the power grounding electrode system at the building or structure served where separate electrodes are used.

...but need to include the water pipe (+phone rod) too

However, the fact your water service isn't bonded to the grounding electrode system violates NEC 250.104(A)(1):

250.104 Bonding of Piping Systems and Exposed Structural Metal.

(A) Metal Water Piping. The metal water piping system shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section.

(1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to any of the following:

(1) Service equipment enclosure

(2) Grounded conductor at the service

(3) Grounding electrode conductor if of sufficient size

(4) One or more grounding electrodes used, if the grounding electrode conductor or bonding jumper to the grounding electrode is of sufficient size

The bonding jumper(s) shall be installed in accordance with 250.64(A), 250.64(B), and 250.64(E). The points of attachment of the bonding jumper(s) shall be accessible. The bonding jumper(s) shall be sized in accordance with Table 250.102(C)(1) except as permitted in 250.104(A)(2) and 250.104(A)(3).

due to the fact that the water system is not bonded to the electrical grounding system, so a short to the water pipe won't trip a breaker or blow a fuse, and also violates NEC 250.50:

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

due to the fact that the water service is a grounding electrode, as per NEC 250.52(A)(1), but is not being used as one at the moment:

(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductor(s) or jumper(s), if installed.

Once that's done, you'll be fine once you replace the rods

Once you have that water-pipe bonding wire fitted (#6 copper is fine for this, by the way, as per NEC 250.53(E)), all you need to do is replace the existing rods with 8' rods, as you propose, in order to fulfill NEC 250.53(D)(2):

(2) Supplemental Electrode Required. A metal underground water pipe shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). If the supplemental electrode is of the rod, pipe, or plate type, it shall comply with 250.53(A). The supplemental electrode shall be bonded to one of the following:

(1) Grounding electrode conductor

(2) Grounded service-entrance conductor

(3) Nonflexible grounded service raceway

(4) Any grounded service enclosure

(5) As provided by 250.32(B)

Exception: The supplemental electrode shall be permitted to be bonded to the interior metal water piping at any convenient point as specified in 250.68(C)(1), Exception.

and bring your grounding system up to full Code compliance.

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  • The op said the primary rod length was unknown so why would it need to be replaced? The 5’ rod as a communications system ground is legal and as I read code required if more than 20’ from the grounding electrode system. Code reff in my answer. – Ed Beal Jan 25 at 2:35
  • @EdBeal -- you need <25ohms or two full size rods when supplementing a water pipe ground with rods – ThreePhaseEel Jan 25 at 2:57
  • The way my jurisdiction reads that is a supplemental rod is needed, ufer, pipe, or plate . For a total of 2 electrodes not 2 rods. – Ed Beal Jan 25 at 3:12
  • @EdBeal -- interesting -- the way I read it is that you need two rods, because 250.53(A)(2) excludes 250.52(A)(1) (aka water pipe electrodes) from consideration as a supplemental grounding electrode to a rod – ThreePhaseEel Jan 25 at 3:35
  • Read the definitions rod, pipe and plate are all equal. I just installed a residential with 1 rod and 1 pipe residential a few weeks back and it passed. My preference is ufer and pipe as they always measure lower. – Ed Beal Jan 25 at 15:43
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There is also the lightning danger. The goal is not to "invite" the lightning to get inside and to destroy many electric/electronic devices in the house - even if not connected to the antenna or TV. A propper surge/lightning protection should be considered and can be complicated sometimes. Another issue is a ground loop which could result from multiple groundings. A 60Hz or 50Hz hum could be picked up by this resulting huge 1-turn transformer and could be fed into the TV and other devices which could result in audible hum or performance issues with other electronic devices. Star like grounding is normally recommended in those cases, but sometimes difficult to match with the lightning protection.

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  • I have never seen a residential surge protector that could stop lightning other than a hit on the power lines a long distance away. A direct hit Will fry the entire electrical system breakers blown through the dead face really nasty, an indirect flash over will likely toast any communications gear even computers on ups and a large whole house surge protector that was mostly ash. I have seen each of these cases 1 time at friends homes that I worked with. Both had modern grounded panels and as we all lived in the country we all had ups’s. – Ed Beal Jan 25 at 2:27
  • @Jason Yes, thanks for the hint, above some xx MHz grounding is no more important for performance reason. Sentence deleted. – xeeka Jan 25 at 3:03
  • @Ed Beal But many commercial antenna systems - f.e. for mobile phones, FM/AM, radar etc. - do protect the equipment from near by lightning hits to some extent. And that does not need to be very expensive, f.e. the coax cable is running in a metal tube that is not connected to the antenna pole above the roof, or the installation of a grounded catch rod or grounded metal mesh above the antenna etc. – xeeka Jan 25 at 3:16
  • @xeeka Commercial is totally different and not a good example here. The standard for communications is in NEC 800 as several of us have pointed out. – Ed Beal Jan 25 at 15:40

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