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Author Topic: Daisy Chain of ground rods  (Read 4317 times)
NW6V
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Posts: 10




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« on: May 01, 2013, 08:06:58 AM »

Hi folks.

Well, my Glen Martin Roof tower is up on the roof, and the cable runs for antenna, control cables and the ground wire are all set.

The ground wire runs down the side of the building to...

There's the question/problem: There is a narrow strip of earth - about 24 inches wide - between the house and the pavement. Please accept as a given that any and all grounding systems - rods and bonding - must run in that narrow strip. There is no reasonable alternative (honest), so let's not rehash "ground rods shouldn't be close to foundation" and such.

A while back, I installed three ground rods in that narrow strip to provide solid grounding for the anti-surge stuff on my inverted-V. The 8' rods are spaced 16' feet apart; one near the antenna/shack location, one at the electric panel, and one in the middle. They are bonded with #6 to each other and the panel, in a daisy chain. 

So far, so good.

Now here's the issue; the ground wire for my Glen Martin tower takes by far the shortest and straightest path to ground - which happens to be just about in the middle of that daisy-chained ground system I already installed. Any other path would be very complicated, and very long, and hence both undesirable and impractical.

So here's the Question: Do I:

a. Drive a separate ground rod for the tower, and run a separate #6 bonding wire to the electric panel? Running the bonding wire will be a chore because it will end up running in parallel to the existing bonding wire with a separation of no more than 6" and perhaps less at a tight squeeze point;

b. Drive a separate ground rod for the tower about 4 feet from the existing center rod, then bond it to the center rod with a short run of #6;

c. Just bond the ground wire to the existing center rod - i.e. into the daisy chain.

Your opinions would be appreciated.

73 Chris NW6V

PS: Antenna arriving today :-)

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K2DC
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« Reply #1 on: May 01, 2013, 08:36:45 AM »

Chris,

   I could be wrong, but I see no reason not to just bond it to the center rod and be done with it.  What you're doing is not really a daisy-chain.  It's no different than bonding individual peices of equipment to a ground buss which serves as a single ground connection.  That's the recommended approach.

73,

Don, K2DC
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KC9NVP
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« Reply #2 on: May 01, 2013, 09:25:41 AM »

If it was my setup, I would ground the tower to the ground rod closest to where the coax enters the shack, as that will be your most common point for all of the grounds and maybe your electrical box.  You say that all of the rods are connected with #6 wire, that's well and good, you can still set your self up with loop circuits that could cause problems connecting to different rods (been there done that with mfg building gorund setups and high power equipments).  In my setup, my equipment is grounded to one ground rod just outside of the access panel that allows the cables to pass thru the wall to the shack.  Off that ground rod, are severall others that move outwards like a spoke of a wheel.  My next step is to connect the outer legs of the spokes together.

David
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K1CJS
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« Reply #3 on: May 01, 2013, 09:26:14 AM »

Just bond it to the closest ground rod.  You've already taken adequate grounding measures of using three rods, now keep the bonding runs as short as possible to minimize resistance.  I believe you'll find that the theory of having one central ground rod that everything is connected to is just that--a theory.  As long as all ground rods are bonded together and bonding runs are kept as short as possible, your grounding system will work as you intend.
« Last Edit: May 01, 2013, 09:30:00 AM by K1CJS » Logged
N6AJR
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« Reply #4 on: May 01, 2013, 11:09:06 AM »

yes, either bond to the closest rod or make a gentle turn and hook in the middle of the wire.  a gentle curve will make the electricity follow better. Also if you are not the talles thing in the air near you, then you should probably not worry so much.  is there power lines, phone poles or street lights  that are taller than your roof tower, in the vicinity. they will "probably" take the hit.
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W5WSS
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« Reply #5 on: May 01, 2013, 11:54:46 AM »

I would attach the antenna and tripod (common to the feed line shield) to the centrally located earthing rod where I would also route the antenna feedline so that I could attach a center conductor lightning arrester there and then continue on routing the antenna feed line to the equipment and not worry about feed line attenuation effecting performance.

I do however have a concern where bonding the other earthing rods to the electrical mains.rod. I would not bond the two separate systems together..I would leave the panel to earthing rod dedicated.to only itself.

I would depend on the distance between the antenna earthing system and the electrical mains earthing system physical separation to minimize an electrical gradient caused by a stroke that is in excess of 11kv. The stroke itself can make the entire area up to a potential that separation helps to prevent by trickling the potential below the discharge quantity preempting it.

How close is the last antenna earthing rod to the electrical panel earthing safety rod?

I do like the three antenna earthing rods being bonded and would use the center rod to attach the arrestor and antenna tripod common with the feed line shield and center conductor arrestor inline.
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N4CR
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« Reply #6 on: May 01, 2013, 12:39:29 PM »

I do however have a concern where bonding the other earthing rods to the electrical mains.rod. I would not bond the two separate systems together..I would leave the panel to earthing rod dedicated.to only itself.

This is contrary to NEC requirements and also could lead to a way for the house wiring to provide the connection between those two grounds. This is why NEC requires that all ground systems be bonded together OUTSIDE the dwelling.

Please don't recommend this to anyone again. It's wrong and dangerous.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
NW6V
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Posts: 10




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« Reply #7 on: May 01, 2013, 01:07:28 PM »

I do however have a concern where bonding the other earthing rods to the electrical mains.rod. I would not bond the two separate systems together..I would leave the panel to earthing rod dedicated.to only itself.

This is contrary to NEC requirements and also could lead to a way for the house wiring to provide the connection between those two grounds. This is why NEC requires that all ground systems be bonded together OUTSIDE the dwelling.

Thanks Phil. I was going to write something to this effect myself just now.

NEC complilance is very important to the XYL and I, both for safety, and for preventing insurance companies from wriggling out of some future claim due to a code violation.

My questions focus on HOW to do the bonding. The code (somewhat ambiguously - which is not uncommon in the NEC) wants each element separatly bonded back to the service entrance ground. But in this case, bacause of the narrow strip in which to operate, separate bonding wires would run in parallel and separated only by inches.

That sounds wrong to me. And attempting to get some other perspective on that is the reason for my post.

I'm inclined to go with C and just bond the teower ground to that existing central post as others have recommended.

73 Chris NW6V

the NEC is famous) A separate wire paralleling the other and separated by just inches? That sounds silly to me; but tht doesn't mean it IS sill

The NEC is explicit about this particular requirement.

But the NEC also doesn't like those bonds back to the
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NW6V
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« Reply #8 on: May 01, 2013, 01:09:09 PM »

"oops" on the undeleted edit junk after my signature :-)
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W5WSS
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« Reply #9 on: May 01, 2013, 01:19:19 PM »

The antenna lightning earthing system in his case is the path of least resistance relative to lightning diversion to earth out there and is best.

The electrical mains earthing rod is a safety ground not a Faraday lightning rod to earthing rod system.

Bonding those rods and the electrical mains panel rod together does not equalize the area about the home relative to preempting a stroke sorry.

Your interpretation although is well intended is your opinion and does not give you the right to speak or order me as you have.

You sir do not represent the final word on this subject and please do not quote Nec specifications to me.

One should always disconnect the equipment from the antenna AND the house wiring when away or prior to stormy weather.

End

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W2RWJ
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« Reply #10 on: May 01, 2013, 04:17:58 PM »


Bonding those rods and the electrical mains panel rod together does not equalize the area about the home relative to preempting a stroke sorry.

Regardless of the logic behind tying the grounding systems together (or not) , it is in the current code, and section 250.94 demands that the electrician install a inter-system bonding termination [IBT] to connect the communications ground to the electrical ground.

73 Martin Flynn
W2RWJ

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W5WSS
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« Reply #11 on: May 01, 2013, 05:01:13 PM »

Bonding the antenna lightning earthing rod to the mains panel earthing rod with a wire  at some unknown distance is unwise.
Bonding the antenna lightning system to the equipment entrance panel is good and was already accomplished at the rod as I suggested deeming an actual entrance panel irrelevant because the rod and connection is accomplishing this task since the fellow routes the feed line after being connected first outside at the antenna earthing rod then he enters the shack.

Having the mains panel (not to be confused with the shack entrance panel) connected to a earthing rod is good.

Connecting the antenna earthing rod to the electrical mains panel and it's earthing rod will not serve the purpose that the fellow is hoping.

A large wire alone encircling the home does a good job but adding rods does nothing to improve the prevention of lightning strikes.

The better alternative is to run wires axially like radial spokes from the antenna earthing rod along with a perimeter wire circling the area.

Bonding the antenna earthing rod to the electrical mains rod is a waste of money.
 
Bonding the station entrance panel and the equipment when including one to the antenna earthing rod or using a bus bar designed for the task accomplishes the same goal and is not a waste of energy time or money.

The important thing is knowing that when the ac mains entrance panel is grounded to an effective earthing rod and the station entrance panel and bonded equipment is connected to the antenna earthing rod then protection is good where either powerlines bring a strike or the antenna they are both serving their function.
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W5WSS
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« Reply #12 on: May 01, 2013, 05:13:11 PM »

I apologise I am wrong the best solution is in fact found when the interconnection between the mains ground panel and the shack entrance panel ground rods are a least path of resistance.
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W5WSS
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« Reply #13 on: May 01, 2013, 05:17:07 PM »

So have an entrance panel and bond the equipment to it then to the shack station rod.
But have a series of radials attached at the below the antenna rod. and a perimeter wire circling the area.
Be sure to make the interconnecting wirelinking the station rod to the mains rod the path of least resistance rather than the house wiring.
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KF7P
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« Reply #14 on: May 01, 2013, 07:17:37 PM »

All grounds must be connected together, both your electrical mains and whatever lightning sytem you put in.  Tom does a good job 'splaining this concept here:   http://www.w8ji.com/house_ground_layouts.htm   Also there isn't anything you can do to "prevent" or "preempt" a lightning hit.  All you can do is give it a place to go if it does choose you (ie, multiple ground rods, buried radials, etc.)

Chris
www.kf7p.com
Custom tower and grounding accessories for amateur radio
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