Grounding Do's Don'ts & Why Part 2

OK in the first part I covered the importance of the Ground Electrode System. Now it is time to put it in details and I can think of no better way than a drawing. Also included are the NEC Article 810 applicable requirements.

So first the supporting NEC 810 requirements:

810.20 Antenna Discharge Units (ADU)

(A) Where Required. Each conductor of a lead-in from an outdoor antenna shall be provided with a listed antenna discharge unit.

Exception: Where the lead-in conductors are enclosed in a continuous metallic shield that either is grounded with a conductor in accordance with 810.21 or is protected by an antenna discharge unit.

(B) Location. Antenna discharge units shall be located outside the building or inside the building between the point of entrance of the lead-in and the radio set or transformers and as near as practicable to the entrance of the conductors to the building. The antenna discharge unit shall not be located near combustible material or in a hazardous (classified) location as defined in Article 500.

(C) Grounding. The antenna discharge unit shall be grounded in accordance with 810.21.

810.21 Grounding Conductors.

Grounding conductors shall comply with 810.21(A) through (K).

(A) Material. The grounding conductor shall be of copper, aluminum, copper-clad steel, bronze, or similar corrosionresistant material. Aluminum or copper-clad aluminum grounding 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 shall not be installed within 450 mm (18 in.) of the earth.

(B) Insulation. Insulation on grounding conductors shall not be required.

(C) Supports. The grounding 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 grounding conductors shall be increased proportionately.

(D) Mechanical Protection. The grounding conductor shall be protected where exposed to physical damage. Where the grounding conductor is run in a metal raceway, both ends of the raceway shall be bonded to the grounding conductor or to the same terminal or electrode to which the grounding conductor is connected.

(E) Run in Straight Line. The grounding conductor for an antenna mast or antenna discharge unit shall be run in as straight a line as practicable from the mast or discharge unit to the grounding electrode.

(F) Electrode. The grounding 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, the grounding conductor shall be connected to the intersystem bonding termination.

(2) In Buildings or Structures with Grounding Means. If the building or structure served has no intersystem bonding termination, the grounding 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 metallic power service raceway

(5) The service equipment enclosure, or

(6) The grounding electrode conductor or the grounding electrode conductor metal enclosures A bonding device intended to provide a termination point for the grounding 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 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)(1).

(1) To any one of the individual electrodes described in 250.52; or

(2) If the building or structure served has no grounding means, as described in 810.21(F)(1) or (F)(2), to an effectively grounded metal structure.

(G) Inside or Outside Building. The grounding conductor shall be permitted to be run either inside or outside the building.

(H) Size. The grounding 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 grounding 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.

Lastly here is NEC 810 shown in a drawing.

 

Great threads!!!

I really like how you are attempting to cut the subject into bite sized chunks.

Extra credit for the drawings, BTW.

 

Thanks Mark, it has to be divided up in steps as it is too comprehensive of a subject to lay out all at once. The most important part is the Ground Electrode System aka GES. It is the foundation in which the rest is built from. and in most cases is all that is needed. Later I will address what goes on inside the Shack.

 

This is good information.
Good reading on a cool cloudy morning.

 

Too comprehensive is an understatement. It's so bad that engineers and electricians nearly come to blows during discussions over the subject. Hard to believe, isn't it? For the unwashed masses, grounding is covered in Article 250 (referred to in 810) and consists of 28 telephone book sized pages with #10 text worded pretty much like the excerpt from Article 810, above.

I do have a question for you, Dereck. On a receptacle, is it supposed to be 'ground up' or 'ground down' ?

(Mark runs and hides)

 

Oh I believe it for sure. I came close to blows as Co-Author of Chapter 9, IEEE STD 1100, aka EMERALD Power and Grounding Sensitive Electronic Equipment.

 

OK I know where this came from Mike Holt, err I mean Mark. That will cost you either a right hook on your left jaw, or a beer. Your choice.

 

I'm glad it's multiple choice. I'll take beer.

 

I don't think the Zedizens know how lucky they are to have you here Elmering us on the subject. Although I know a bit about you, the rest may just see you as a newbie with less than 500 posts.

Zedizens, hear this:

Dereck knows his stuff. I know him from another forum (Mike Holt's NEC code forum for professionals, not amateurs ) Hopefully he will stick around here to become a regular. The other forum is the very best forum on the planet for the electrical profession and the owner of the site is the author of perhaps the most popular NEC code update classes in existence. Dereck is one of the moderators there. I didn't know he was a ham until today.

Again, thanks to Dereck for sharing his knowledge with us and hopefully destroying some myths in the process.

 

I truly appreciate the explanations given here. And how they can (or should be) implemented.

So, in all honor and explanations, HOW do I explain "Coffee grounds" to our recent licensees?

I just explain they are a product of the boat anchors from tune bygone daze.

With all facetiousness aside, we (Associated Radio Amateurs of Long Bach CA, INC,) just finished another Tech Class training session, and have an overall "pass" rate over 90% for all of our (Tech AND General Class) students, through the greater Los ANgeles CA. area. We are (apparently) the ONLY ARRL affiliated club that will be providing Amateur Extra class preparation training sessions this side of the Mississippi River at this time in 2012.
It is a service and commitment we want and need to provide as an ARRL Special Service Club.

Look up : ARALB.org, and our club station: W6RO on QRZ for details.