Off grid grounding technique?

icarus · August 2009

Re: Off grid grounding technique?

I've been taught since childhood to disconnect and ground the antenna leads during a storm, but I confess I have gotten out of the habit. I'm sure I will pay the price some day.

Tony

benthere · August 2009

Re: Off grid grounding technique?

I bet you could use a switch or two, so that throwing the switch moves the connection to ground rather than the equipment. The question then would be, would it introduce notable interference with normal operation of the equipment, and would the contacts be far apart enough to do you any good in case of a strike. But it would be easier to throw a switch or few than disconnect several coax cables. How about another AB switch on which one side goes to ground?

mike95490 · August 2009

Re: Off grid grounding technique?

A switch with a 1/2" gap, is nothing to a bolt that came 4,000 feet out of the sky.
Should have disconnects outside, rather than invite it to follow the wire into the house.

BB. · August 2009

Re: Off grid grounding technique?

Also, Lightning is a high frequency (10kHz or so for most of the energy--like AC) energy.... It is impedance of the path (and ionization of air, etc.) that control the path it will take. Not pure DC resistance.

You can get some very surprising effects (such as lightning does not like to follow sharp bends).

The recommendations to have a 10' minimum separation (if that is your plan) between a lightning "receptor" and your protected property is a realistic minimum.

The 60 meter (~200 foot) radius "rolling ball" (earlier posts) is an interesting way to look at the variable nature of lightning and the fact that any distances (differences between attractors) less than that are meaningless when looking at the initial strike points.

-Bill

niel · August 2009

Re: Off grid grounding technique?

benthere wrote: »

I bet you could use a switch or two, so that throwing the switch moves the connection to ground rather than the equipment. The question then would be, would it introduce notable interference with normal operation of the equipment, and would the contacts be far apart enough to do you any good in case of a strike. But it would be easier to throw a switch or few than disconnect several coax cables. How about another AB switch on which one side goes to ground?

they do have switches that can go straight to ground like these,
http://www.alphadeltacom.com/pg3.htm
note in the picture the center position as that is to ground. i have one of these, but mine does not have an arc plug which is a gas discharge tube for dissipating lightning. once those tubes fire they are junk and prone to a secondary event with no protection.

icarus · August 2009

Re: Off grid grounding technique?

My guess is that any AB switch is going to get fried with a direct hit. I also think that the little coax lightning arresters are also likely to get fried, only question is will they dissipate enough energy to save the radio, or more importantly the building.

I have ordered some coax lightning arresters,, we'll see what happens.

T

niel · August 2009

Re: Off grid grounding technique?

unfortunately their is no guarantee even if you had no radios at all. lightning does whatever it wants to and a direct strike is dangerous no matter what.
look at it another way, the antenna and coax is going to fry too just like a fuse so why worry about the switch or the arrestor as none of it can handle a full stroke?

icarus · August 2009

Re: Off grid grounding technique?

No, my point was that while the switch could provide SOME path to ground, a direct hit was going to fry everything from the Antenna to the radio, so while the switch and the ground MIGHT help, a direct is is going to burn stuff up no matter what. Thinking that a Tiny CATV AB switch could effectively divert enough lighting to save the radio is, I think, wishful thinking.

T

CaribSoul · August 2009

Re: Off grid grounding technique?

We have a family cabin not far from Tony's place and are dealing with the same kind of soil conditions with respect to grounding--i.e. very little soil on top of bedrock! Our system components are on their way to the cabin as we speak and my son will be starting construction this weekend. Fortunately, he is a licensed electrician who has been working for a lightning protection company and has about 20 years of experience with grounding. He sent me an email this morning with a brief description of his grounding plan, so I thought I'd jump in and share it with the group:

"I am dong a tripod ground with a 2' X 2' solid copper ground plate in the middle, encased in a special enhancement material called Lycolnite III, which is a combination of bentonite, salt and other metaillic ground enhancement materials. There will then be two 12’ copper leads extending from the plate, buried in 18” of topsoil. There will actually be two of these arrays, one at the front of the cabin and one at the rear. It is far more reliable than lake water and the strike would actually have dissipated long before it reached the lake anyway. I would be shocked (pun) if we had higher than a .05 ohms resistance reading after this procedure. Just as a gauge, Army Corps Of Engineers’ spec requirement is 5 ohms. I plan to do a full resistance test on the completed system. I’ll send you the final numbers."

His design is a bit different than what has been discussed up to this point. If there are questions, I'll relay them to my son and post his answers when he has the opportunity to communicate from the remote cabin location! He doesn't spend much time on forums, so I'll be the designated go-between.

Cheers,
Chris

niel · August 2009

Re: Off grid grounding technique?

good to hear more on this. tony is right at the lake so how far from the lake are you?

CaribSoul · August 2009

Re: Off grid grounding technique?

When we bought (or should I say, leased from Queen Elizabeth?) the property in the mid 60's, there was a 60-ft setback from the lake that was "public access"--so we had to build farther back. We are not on an island like Tony. The cabin is perched on a large flat rock, with the front about 100 ft (30 meters) from the water. The lake bottom is muck, probably conductive, as has been discussed. But my fear is that the resistance of even a fairly large #4 cable might be too high to be an adequate ground at that distance to give much lightning protection. The resistance measurements that my son takes when he has the grounding system in place will let us know if his design is successful.

Chris

icarus · August 2009

Re: Off grid grounding technique?

Chris,

You have two advantages over me. You have 18" of top soil, and your lake bottom is muck. We have no real top soil, and our lake shore is bare granite, covered in some places with boulders.

T

CaribSoul · August 2009

Re: Off grid grounding technique?

I think the "18 inches of topsoil" may be a little optimistic! The only place I'm sure has that much--and more--is where we have the biffy! There's a lot of exposed rock around the cabin.

My son has most likely arrived at his cousin's place for the night by now and will make the final push over the border to the cabin tomorrow. He did take the time to elaborate on the lightning/grounding issue (presumably while my daughter-in-law was driving!). Here's what he had to say:

"Happy to share the knowledge. You can also post our Material Sales guy’s phone number and email address, should anyone want to inquire about parts. (chuck.neve@vfcinc.com) 801-512-5824. We also own a grounding engineering firm in LA called Lyncole XIT.

There’s a huge price, and conductivity issue with running a straight ground lead to the lake. Starting with the fact that class I copper lightning conductor is about $2.08 USD per foot, where as a couple of ground plates and some ground enhancement material is much less expensive, and more effective.

Another means acceptable to UL and the NFPA for current dissipation in shallow or crappy soil conditions--and more widely used--is a counterpoise or ground loop conductor, which is a main-sized copper conductor encircling the structure, buried as deep as possible, OR laid directly on top of bedrock and anchored every three feet. It is important to remember that the 3 main lightning protection/grounding standards, UL-96a, NFPA-780 and LPI-175, never offer a water source as an acceptable ground terminal for a structure. Only NFPA-780 mentions water in this capacity at all, and it is for WATERCRAFT ONLY.

I myself, would not recommend or use a body of water as an acceptable ground source. It’s conductivity and consistency, in this capacity, is really questionable to me.

It is also important to remember that secondary bonding of grounding or lightning protection conductors is critical. Every piece of potentially grounded, conductive material in a structure needs to be bonded, at least one time, to the grounding electrode. Failure to do this will leave these items at different potential and exposes the entire structure to secondary current literally jumping between these potentials--and setting fire to anything in its path. Picture huge arcs jumping around the house from the gas line to the kitchen sink to the fireplace. This is the risk taken when these conductive bodies are not bonded to the system.

You can also add that a surge suppressor without a complete, structural lightning protection system, or vice versa, is pointless, one has little or no impact without the other.

Feel free to edit and post accordingly--Jeff"

I'll add more as I get progress reports during the construction!

Chris

icarus · August 2009

Re: Off grid grounding technique?

Chris,

Thanks for the info,

Couple of questions, What is a "main sized" conductor? Is it like a 2/0 conductor encircling the house?

My problem is I have bedrock, but on places it is impossible to dig to. Picture a barge load of boulders ranging in size from bowling balls to VW's dumped on top of the bedrock, and then having 10,000 years (since the ice retreated (age not last winter!) of forest duff to accumulate on top of it. Digging with hand tools is not an option. So stringing a wire around the house, trying to bury it around the building, and then anchoring it where the bedrock is exposed is, to put it mildly, aint gonna happen!

So,,,,I guess I am back to square one. I do have one advantage in that I have no metal gas pipe coming in the building (save a few feet under the building where it transitions from plastic) No metal water piping and no wiring outside the building. So bonding metal is not too much problem. I do think that keeping the battery/120vac neutral buss off the lightning ground SEEMS like a good idea.

I would be interested in hearing more from your Son on the matter, as he does this for a living.

Tony

niel · August 2009

Re: Off grid grounding technique?

chris,
there's no way that just laying a conductor around a house on rock is going to offer adequate protection by itself and to say this by itself outweighs going to the lake with using that perimeter protection too is ludicrous. it doesn't matter if nec or whoever dictates against a lake it is common sense here that he needs to take it to the best place to dissipate that lightning. a ground screen is fine if nothing more is available, but he has the ability to dissipate a great deal of power in that lake that just won't happen with only a screen or perimeter wire on the rocks.
the whole idea is to pass the power into the ground as best as you can. with some soil at your location (not tony's) this will afford some transfer of power using a ground screen or a perimeter wire buried (although deeper and more soil would be better) and 100ft to the lake would be too far for you to carry as a good ground point by itself, but it is possible that the buried perimeter wire can continue on in that soil to the lake for additional grounding. that would just be a good extension off of the screen for you.
also note that i did say to put the ground rod into the lake bed and not just the water for multiple reasons. if there's little soil in the lake bed and only rock, then i see the lake bed as the better place to lay wire than just lying on top of the rocks around his place alone.
we are in complete agreement on the issues of bonding and perimeter protections that tony just does not want to do. this is why i suggested the faraday shield and bonding the metal roof to it at least on the top. technically each part of the metal roof needs bonded to the next and to ground or the sparks can fly, but i also think it'll travel down his stove stack to the stove inside before he'd need to worry of the minor potential differences to the roof. this may also be said of the antennas and cables too as it is an introduction inside his place to those high potentials.

icarus · August 2009

Re: Off grid grounding technique?

Niel,

It's not that I don't want to do anything, it is just that I have issues as to the right way/cost effective/aesthetic/doable way to do it.

Lake shore is the same boulder field on top of bed rock for ~10' then drops off to almost bottomless with in another 10'. No where can I find muck. Nice lake bottom, clear water, but no way to bury a ground rod in the muck.

T

niel · August 2009

Re: Off grid grounding technique?

that's my point that you can't bury it on top of the boulders above the water effectively either even though the screen or perimeter wiring laying on the rock and anchored every 3ft may meet code. that code is a compromise when nothing else better is available and you have something else available that's better than code would otherwise dictate. so if it has to lay on boulders then i say the better of the 2 is to have it on the boulders in the water. a few boulders can hold it down there better than above the water too, but i'd still use a rod.
everybody will make this a battle of what you should do, but think and decide what you want to do as there aren't any ways to fully guarantee taking a full strike regardless of how far you go with it all.

BB. · August 2009

Re: Off grid grounding technique?

Actually, I agree with the ring around the cabin... That, plus Lightning rods around the cabin (per the various specs.) and conductors running down the corners of the building to the ring is building a Faraday Cage.

Assuming there the spec. (such as Mike's Link) is followed so that all points of the building are under lighting arresttors (spaced per recommendations) and tied with rated cable... There is no place a bolt cannot strike that is not electrically bonded to every other point (including the ring around the building).

Like Charge and Like Currents tend to repel each other--spreading charge equally around the "outside" of the cage--and the currents tend to flow as far apart from each other as they can (skin effect on the micro AC scale, conductors on opposite corners of buildings on the macro scale).

The idea of a Faraday Cage is not to dissipate the energy--it is to equally distribute the charge around the cage. So that anyone inside the cage cannot measure any currents or chargers because everything is at the same level.

Of course, the definition of the cage "grid" is based on frequency... For very high frequencies, the grid (if using copper mesh) must be very small (see holes in a microwave oven which is ~2.45 GHz or higher--1/4 wave length (calculator looks OK--did not verify) is 1.2 inches / 31 mm which is the minimum size for a "leak"). When working in screen rooms, we used fairly fine copper mesh because we wanted >1 GHz isolation--and even then, because we were bringing power cords and antenna leads through the "wall"--it was not perfect.

If we assume that we need to protect against a 10kHz lightning strike (there is energy upwards of 1MHz)--the 1/4 wave length would be 24,000 feet (1 MHz is 246 feet).

Lightning, which has much of its energy below 10 kHz then--any copper conductors (that is appropriate construction--i.e, large diameter with multiple strands) equally spaced around the cabin would look like a Faraday cage (even 1MHz and 1/4 wavelength of 246 feet is still large compared to a cabin)...

So--now that you have a Faraday Cage--you really don't care where the charge/energy goes from the strike (if you are inside the "cage" and there is nothing outside -- nearby -- that you care about.

That is, as long as the internal metal objects in the building are bonded to the lightning cables on the outside of the building (again, see Mike's link).

If Tony had (for example) power lines coming in, water and gas mains, etc. (we know he has a radio mast)--having a poor ground for the Cabin probably make for more issues with potential differences in voltage (i.e., water faucet is energize with respect to the rest of the "Faraday Cage").

But, because he is off-grid--his Fariday Cage violations are kept to a minimum--and his protection could be much better.

Getting the lightning to "earth ground" is not a bad idea--but in Tony's case, Chris' son's recommendations are good (in my humble opinion).

Going to extremes to get an "earth ground" where none really exists is not going to help a lot.

I am not a HAM--but a good earth ground is useful to have a ground plane for better antenna performance (properly shaped radiation pattern)--Isn't it?

When we grounded our test sites and DUT's (for FCC emissions testing) it was not to reduce the emissions (and pass the tests), it was to provide a good reference plane so that we would have more consistent results between test sites and labs.

-Bill

icarus · August 2009

Re: Off grid grounding technique?

OK,

Hows this sound as an idea. Clamp a braided copper or aluminum braided lighting wire on the antenna mast and the stovepipe. Send this down the side of the building, and into the lake. Clamp the dead end of this to a copper ground rod, and bury it in under the rocks in the deepest water I can. Take the neutral (panel) ground #4 and carry it into the lake on it's own ground wire separated by some feet from the major braided ground.

When I add the steel roofing, bond this wire to the steel, and add a #4 copper on all four corners of the building on to the earth and then into the lake.

What say you all?

T

niel · August 2009

Re: Off grid grounding technique?

bill,
look at the picture of tony's place. it takes more effort for a screen than to put the ground lead into the water so this is not going to extremes to get a good ground of which imho, there is no good ground at present. i totally agree on the faraday cage bill, but i think it is more confusion or missunderstanding on his part as to what it is and involves. screening is not needed, as you tried to point out, and it would cover the frequencies needed for the lightning and thensome with it coming down the 4 corners. i still agree with the perimeter wiring of the ground, but i contend it shouldn't stop there. it can't go to rods in the soil as it should and a ground screen is more work and less effective than the lake just a few feet away.
ground screens are not all that good as grounds when on rock as is the case of the perimeter wiring too for there is little actual contact with the earth and hence it is a high resistance. your example of a 'ground plane antenna' is offbase as rf grounds differ from an earth ground. for the record, acceptable utility grounds are always a compromise and definitely don't do well to dissipate lightning unless spread out among many poles and homes to get the overall low resistance sinking of such events.

BB. · August 2009

Re: Off grid grounding technique?

If you follow the link--the minimum "screen mesh" to protect an average building (i.e., not making black powder inside) is something like 10x20 meters (really just the lightning copper cabling + lightning rods).

And--more or less, I am treating lightning as RF current (nominally 10 kHz and lower)...

If there is earth around the place, use it. I guess it won't hurt to run a cable into the water/muck--but it appears that it will not help much.

Also, I think he was respecting the fact that proper cable is $2.08 per foot... Not cheap and could be a waste of money to toss a length of cable into the lake.

-Bill

niel · August 2009

Re: Off grid grounding technique?

he admitted to having plenty of cable. i think he said 1000ft of #4, but he certainly won't need that much of it unless he does do ground screening. #4 would do very well for his grounding application. he may need about 15-20ft more #4 to put some into the water over what you already proposed for him to do.
given the choices between boulders with little to no soil and a lake, the lake has the better conductivity by far and quit thinking like wiles by thinking yourself into the same ruts he does.

icarus · August 2009

Re: Off grid grounding technique?

Hey guys,

You're talking like I'm not here!

I understand (well, sort of understand) the concepts. What I am not clear on is the proper wire array to make an effective cage.

Tony

niel · August 2009

Re: Off grid grounding technique?

my responses in bold. actually the hard part is picturing what i'm saying as it really is simplistic in reality.

icarus wrote: »

OK,

Hows this sound as an idea. Clamp a braided copper or aluminum braided lighting wire on the antenna mast and the stovepipe. Send this down the side of the building, and into the lake. Clamp the dead end of this to a copper ground rod, and bury it in under the rocks in the deepest water I can. Take the neutral (panel) ground #4 and carry it into the lake on it's own ground wire separated by some feet from the major braided ground.

this sounds ok, but the neutral is not a separate ground and ties to ground prior to going to the lake. you need to pick 1 point of connection as you don't want neutral to tie to ground in multiple points.

When I add the steel roofing, bond this wire to the steel, and add a #4 copper on all four corners of the building on to the earth and then into the lake.

i believe you are still missing the visualization of what i was trying to convey to you. are you familiar with those lightning rods some buildings have on top of them? picture 2 of them, one on the left side of your house roof and one on the right side of your house roof. the wire is to come down the front corners of your house to the ground. normally the ends would meet a ground rod at the soil and tie together underground, but instead i proposed these to go to the lake and both tie to a ground rod there. what you will need to do is make another wire come off of each lightning rod and down to the left rear and right rear corners of your house. when they reach the ground level they are to come forward at ground level and meet the bottom of the front ground wires that had come down. this can be bonded together (front + rear left and front + rear right) with split bolts. you could also bond left rear with right rear on the ground and left front with right front on the ground to make the completed perimeter wire. i feel the front one can be skipped, but the back one may be a good idea.
at this point the left and right side of the house's lightning rods on the roof should get bonded together (split bolts again) with the wire going across the top. the cage and lake ground at this point is completed. the antennas can then be addressed and grounded to anywhere along that top wire or if more convenient it can attach to one of the cage downleads. remember to have no sharp bends in the wires.
the metal roofing can later be tied to the cage wires, but remember copper and other metals will have a reaction (galvanic) so protect the copper from contacting dissimilar metals.

What say you all?

T

btw, sorry about it seeming like i was ignoring you as it is difficult to explain to one person what it is you have in mind and being interrupted with theory and proposals from others and having to explain moreso to them. it's like too many chefs in a kitchen trying to do 1 meal.:roll: it was late when bill and i were doing that too.

icarus · August 2009

Re: Off grid grounding technique?

I think I got it,,, for now anyway.

My 120 panel has a neutral buss bar that is common to the grounded buss bar, so they both share the same ground. These are in turn bonded to the breaker box. I assume that this is the proper way to do it.

Tony

dwh · August 2009

Re: Off grid grounding technique?

<OFF_TOPIC>
Okay, let me just take a moment to say that this is another of those "I LOVE THIS THREAD" threads.

When I get to learn things I didn't know, I love it.

It is exactly discussions like these, with the contributions and expertise just flowing in - in this case from the son of a forum member *through* the forum member - which makes this site/forum such an enormously valuable resource. I certainly hope that NAWS has got their backups handled properly, because it would be a crying shame to lose this data.

I love this thread.
</OFF_TOPIC>

niel · August 2009

Re: Off grid grounding technique?

ok tony i think you have the jist of everything, at least i hope.:roll:

dwh,
i'm almost afraid to ask what it is you learned.
i know i learned how to go around the world to get 15-20ft farther.;):D

dwh · August 2009

Re: Off grid grounding technique?

icarus wrote: »

I think I got it,,, for now anyway.

My 120 panel has a neutral buss bar that is common to the grounded buss bar, so they both share the same ground. These are in turn bonded to the breaker box. I assume that this is the proper way to do it.

Tony

Yes, that's proper. Neutral should be bonded to ground at the main panel.

This is not true for sub-panels however...sub-panels should not have the neutral and ground bonded together.

All metal boxes are considered part of the "grounding system" and every metal box should be connected to ground.

(Neil,

What I learned was a great deal about lightning grounding systems. I have never dealt with them myself, so my knowledge was limited to remembering seeing lightning rods on each end of my uncle's gable roofed farmhouse and barn in Arkansas when I was a boy. I remember these had thick bare copper wire running down from the rods to ground rods driven in the ground. I also remember that when I asked my uncle what they were, and he told me, the whole idea seemed damned scary.)

bobdog · August 2010

Re: Off grid grounding technique?

I know this thread is a year old, but I can't help but wonder what ever happened to your cabin Chris?

And Tony, what did you finally decide to do?

I am mostly curious as now I have to figure out what I am going to do with regards to grounding and lightning protection.

Tim

CaribSoul wrote: »

I think the "18 inches of topsoil" may be a little optimistic! The only place I'm sure has that much--and more--is where we have the biffy! There's a lot of exposed rock around the cabin.

My son has most likely arrived at his cousin's place for the night by now and will make the final push over the border to the cabin tomorrow. He did take the time to elaborate on the lightning/grounding issue (presumably while my daughter-in-law was driving!). Here's what he had to say:

"Happy to share the knowledge. You can also post our Material Sales guy’s phone number and email address, should anyone want to inquire about parts. (chuck.neve@vfcinc.com) 801-512-5824. We also own a grounding engineering firm in LA called Lyncole XIT.

There’s a huge price, and conductivity issue with running a straight ground lead to the lake. Starting with the fact that class I copper lightning conductor is about $2.08 USD per foot, where as a couple of ground plates and some ground enhancement material is much less expensive, and more effective.

Another means acceptable to UL and the NFPA for current dissipation in shallow or crappy soil conditions--and more widely used--is a counterpoise or ground loop conductor, which is a main-sized copper conductor encircling the structure, buried as deep as possible, OR laid directly on top of bedrock and anchored every three feet. It is important to remember that the 3 main lightning protection/grounding standards, UL-96a, NFPA-780 and LPI-175, never offer a water source as an acceptable ground terminal for a structure. Only NFPA-780 mentions water in this capacity at all, and it is for WATERCRAFT ONLY.

I myself, would not recommend or use a body of water as an acceptable ground source. It’s conductivity and consistency, in this capacity, is really questionable to me.

It is also important to remember that secondary bonding of grounding or lightning protection conductors is critical. Every piece of potentially grounded, conductive material in a structure needs to be bonded, at least one time, to the grounding electrode. Failure to do this will leave these items at different potential and exposes the entire structure to secondary current literally jumping between these potentials--and setting fire to anything in its path. Picture huge arcs jumping around the house from the gas line to the kitchen sink to the fireplace. This is the risk taken when these conductive bodies are not bonded to the system.

You can also add that a surge suppressor without a complete, structural lightning protection system, or vice versa, is pointless, one has little or no impact without the other.

Feel free to edit and post accordingly--Jeff"

I'll add more as I get progress reports during the construction!

Chris

icarus · August 2010

Re: Off grid grounding technique?

Short answer is nothing. The grounded bus of the 120 vac panel and the 12 vdc negative side ground to a separate ground wire strung through the bush to a ground rod buried as deep in the "soil" as possible. I also used uninsulated wire for the last ~50' of ground wire to add to any conductivity to ground.

The antennas and the building are grounded into the lake, with a zinc clad ground rod dropped into ~30" of water, sitting on the bottom of the lake. Not perfect, but we haven't had a problem with such a system.

Off grid grounding technique?

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