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Aluminum as a ground system
A new commercial radio hilltop vault is being installed in my area.... and the contractor has installed the tower and vault ground ring with aluminum wire/cable, I have been advised. I do NOT know the gauge of the wire, but I am curious what your thoughts are on this issue. I have been involved the past 35 years of my career in a number of ground installations and every one of those used large copper cable... no aluminum anywhere. The last of these I saw was 6 or 7 years ago. QUESTION: Are aluminum ground systems becoming common? Are they reliable, even after absorbing some heavy strikes? Any other comments? Ed K7AAT on the Oregon Coast .. .. |
Aluminum as a ground system
"Ed" wrote in message . 192.196... A new commercial radio hilltop vault is being installed in my area.... and the contractor has installed the tower and vault ground ring with aluminum wire/cable, I have been advised. I do NOT know the gauge of the wire, but I am curious what your thoughts are on this issue. I have been involved the past 35 years of my career in a number of ground installations and every one of those used large copper cable... no aluminum anywhere. The last of these I saw was 6 or 7 years ago. QUESTION: Are aluminum ground systems becoming common? Are they reliable, even after absorbing some heavy strikes? Any other comments? Ed K7AAT on the Oregon Coast Isn't aluminium in the presence of air naturally coated with a thin layer of aluminium oxide which doesn't conduct? In which case aluminium might be fine for lightning conductors but hopeless for RF. What will the tower carry? ... if it's all VHF and upwards then there's probably no problem. Chris |
Aluminum as a ground system
Ed wrote:
A new commercial radio hilltop vault is being installed in my area.... and the contractor has installed the tower and vault ground ring with aluminum wire/cable, I have been advised. I do NOT know the gauge of the wire, but I am curious what your thoughts are on this issue. I have been involved the past 35 years of my career in a number of ground installations and every one of those used large copper cable... no aluminum anywhere. The last of these I saw was 6 or 7 years ago. QUESTION: Are aluminum ground systems becoming common? Are they reliable, even after absorbing some heavy strikes? Any other comments? Ed K7AAT on the Oregon Coast My only experience with an aluminum wire ground system was one I laid many years ago in Denver, with buried aluminum radials. It was pretty badly corroded in a few years. But the soil there is alkali, not like the acid soil you have on the coast. Interestingly, aluminum corrosion is minimum at a pH of about 5.5 (see http://www.tpub.com/content/doe/h101...015v1_121.htm), which is likely roughly what your soil is. So while there might be a lot of places where corrosion would be a problem your location might be one of those where it wouldn't. Roy Lewallen, W7EL |
Aluminum as a ground system
christofire wrote:
Isn't aluminium in the presence of air naturally coated with a thin layer of aluminium oxide which doesn't conduct? In which case aluminium might be fine for lightning conductors but hopeless for RF. What will the tower carry? ... if it's all VHF and upwards then there's probably no problem. Chris Yes, aluminum is immediately coated by a few-molecule-thick layer of aluminum oxide when exposed to air. It's a non-porous, brittle, ceramic material commonly used for hybrid circuit substrates and for sandpaper grit, among other things. It's why aluminum, despite its extreme chemical activity, doesn't corrode -- unless the environment is capable of dissolving the aluminum oxide, which some are. Aluminum oxide is an excellent dielectric, into at least the microwave range. But an insulating film doesn't make a conductor "hopeless" -- after all, the most perfect bare conductor is surrounded -- "coated" if you will -- by air. Nor does a highly conductive coating degrade a conductor's performance. Only a layer of poorly conductive material of sufficient thickness is detrimental. Roy Lewallen |
Aluminum as a ground system
I am only interested in the long term reliability of an aluminum ground system in comparison to the more common copper system. This is for lightning suppression only, I am not addressing RF issues. I am wondering if aluminum can handle the potential surge currents that copper can... and how well does its ground conductivity work when buried, when compared to copper. Ed K7AAT |
Aluminum as a ground system
Ed wrote:
I am only interested in the long term reliability of an aluminum ground system in comparison to the more common copper system. This is for lightning suppression only, I am not addressing RF issues. I am wondering if aluminum can handle the potential surge currents that copper can... and how well does its ground conductivity work when buried, when compared to copper. For surge currents only, Al would need to be thicker than Cu of equal handling capacity. If you are stressing things to the max, Al has a lower melting point. It would work for RF ground also. The oxide layer would not affect the performance. Lots of us use insulated copper wire for ground radials. Only concern I would have is that the electrical connections are properly made. AL's talent for oxidizing has been a problem in the past with house wiring. - 73 de Mike N3LI - |
Aluminum as a ground system
"Michael Coslo" wrote in message ... Ed wrote: I am only interested in the long term reliability of an aluminum ground system in comparison to the more common copper system. This is for lightning suppression only, I am not addressing RF issues. I am wondering if aluminum can handle the potential surge currents that copper can... and how well does its ground conductivity work when buried, when compared to copper. For surge currents only, Al would need to be thicker than Cu of equal handling capacity. If you are stressing things to the max, Al has a lower melting point. It would work for RF ground also. The oxide layer would not affect the performance. Lots of us use insulated copper wire for ground radials. The OP referred to a 'vault ground ring', not radials. Furze is a major supplier of lightning protection products in the UK and they don't favour aluminium for earth connections: http://www.furse.com/elp/earprod.htm. I understand copper and copper-plated-steel is still used for neutral earth connections by UK electric power supply companies as well - the oxide layer on aluminium and its alloys, if present, must have some value of breakdown voltage and anything that elevates neutral above earth that can be avoided has to be a bad thing. Chris |
Aluminum as a ground system
In article 8,
Ed wrote: I am only interested in the long term reliability of an aluminum ground system in comparison to the more common copper system. This is for lightning suppression only, I am not addressing RF issues. I am wondering if aluminum can handle the potential surge currents that copper can... and how well does its ground conductivity work when buried, when compared to copper. Ed K7AAT For Lightning Protection Aluminum is NOT the grounding material of choice. Higher resistance per foot. (Less conductivity) and the Oxide boundary layer, make it unsuitable for this type of use. For RF Grounding use, it will work just as well as copper as the Oxide layer really has no effect at RF Frequencies. |
Aluminum as a ground system
In article ,
Michael Coslo wrote: Only concern I would have is that the electrical connections are properly made. AL's talent for oxidizing has been a problem in the past with house wiring. A good point. The National Electric Code has some fairly specific requirements for how grounding system connections must be made. Soldering is not permitted, as the high temperatures which can occur at such connections during a lighting strike can blow the soldered connection apart. Strong mechanical connections, or welding (e.g. "CadWeld" thermite-type welding) is required. I just ran across the following: http://www.homeinspector.org/resourc...-Grounding.pdf It indicates that the NEC forbids the use of aluminum conductors for grounding "where in direct contact with masonry or earth. Aluminum conductors require 18 inches of clearance from earth." (NEC paragraphs 250-91a and 250-92a are cited). There's also a note on the citation: "ATJ note: we have field reports of complete failure of uninsulated bare aluminum grounding conductor wire when it was not properly protected from corrosion - for example where left touching a masonry foundation wall." It sounds to me as using aluminum wire as a lightning ground system is a poor idea. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Aluminum as a ground system
Below is good information, but only applies to electrical systems' grounding... not commercial radio vault lightning ground systems. Also, the aluminum system I came across certainly had crimp or other mechanical bonding methods which avoids the connection issues discussed in the NEC. I have no control or great concern on this, but was surprised to see aluminum for my first time. I just wondered if it was common. Ed K7AAT .. The National Electric Code has some fairly specific requirements for how grounding system connections must be made. Soldering is not permitted, as the high temperatures which can occur at such connections during a lighting strike can blow the soldered connection apart. Strong mechanical connections, or welding (e.g. "CadWeld" thermite-type welding) is required. I just ran across the following: http://www.homeinspector.org/resourc...lectrical-Grou nding.pdf It indicates that the NEC forbids the use of aluminum conductors for grounding "where in direct contact with masonry or earth. Aluminum conductors require 18 inches of clearance from earth." (NEC paragraphs 250-91a and 250-92a are cited). There's also a note on the citation: "ATJ note: we have field reports of complete failure of uninsulated bare aluminum grounding conductor wire when it was not properly protected from corrosion - for example where left touching a masonry foundation wall." It sounds to me as using aluminum wire as a lightning ground system is a poor idea. |
Aluminum as a ground system
On 22 Sep 2009 23:19:40 GMT, Ed
wrote: QUESTION: Are aluminum ground systems becoming common? Are they reliable, even after absorbing some heavy strikes? Any other comments? Ed K7AAT on the Oregon Coast I've never seen any that use aluminum wire. Everything I've seen and what little I've done was copper wire for both mountain top and home grounding. The National Fire Protection Association (NFPA) has guidelines such things. See NFPA 780 "Standard For Installation Of Lightning Protection Systems 2004". It describes protection for people, building, and property from lightning damage. http://www.atmo.arizona.edu/students/courselinks/spring07/atmo589/articles/NFPA_780_2004.pdf 1.1MByte PDF. Several sections mention aluminum use. Googling merrily... http://everything2.com/title/aluminum+wire The only problem you have to consider is that you cannot allow the wire to enter the structure because exploding aluminum can cause a fire. http://electrical.about.com/od/electricalsafety/a/lightningprotectionlightningrods.htm The underground connection to the lightning protection system must be made with copper wire because underground connections should not be made with aluminum wire. Aluminum wire will corrode when placed in the ground. The National Electrical Code requires the aluminum wire connection be at least 18 inches above the ground [NEC Section 250.64(A)] with a bi-metal splice. This connects to an eight-foot copper ground rod at least two feet from th home's exterior wall. There must be a minimum of two ground rods installed to the system on opposite ends of the home, with one near the service entrance ground rod so it can be bonded to this ground rod. This ensures that there is a common ground between all ground rods. This should make the connecting copper wire length between the ground rod and aluminum cable approximately four feet long. Place the ground rods diagonally on either end of the house, not exceeding 100 feet between the two ground rods. If this distance is exceeded, additional ground rods must be added to ensure proper grounding. http://www.glenmartin.com/catalog/lightning.htm They use copper wire, but the lightning rod points are aluminum. http://www.lightningrodparts.com/faq.html (13) Will Aluminum Wire/Cable and Rods work as well as Copper? It should as long as the installation rules are followed. Certainly Copper is a better conductor than aluminum but the Aluminum cable is larger than the copper therefore making up for aluminum's lesser conductivity. (24) BASIC INSTALLATION DETAILS: No Structure shall have less than 2 ground rods (Aluminum wire should not be underground) -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Aluminum as a ground system
On Sep 24, 1:56*pm, Ed wrote:
* *Below is good information, *but only applies to electrical systems' grounding... not commercial radio vault lightning ground systems. *Also, the aluminum system I came across certainly had crimp or other mechanical bonding methods which avoids the connection issues discussed in the NEC. * *I have no control or great concern on this, but was surprised to see aluminum for my first time. *I just wondered if it was common. * *Ed * K7AAT . The National Electric Code has some fairly specific requirements for how grounding system connections must be made. *Soldering is not permitted, as the high temperatures which can occur at such connections during a lighting strike can blow the soldered connection apart. *Strong mechanical connections, or welding (e.g. "CadWeld" thermite-type welding) is required. I just ran across the following: *http://www.homeinspector.org/resourc...lectrical-Grou * nding.pdf It indicates that the NEC forbids the use of aluminum conductors for grounding "where in direct contact with masonry or earth. *Aluminum conductors require 18 inches of clearance from earth." *(NEC paragraphs 250-91a and 250-92a are cited). There's also a note on the citation: *"ATJ note: *we have field reports of complete failure of uninsulated bare aluminum grounding conductor wire when it was not properly protected from corrosion - for example where left touching a masonry foundation wall." It sounds to me as using aluminum wire as a lightning ground system is a poor idea. The only time in my life that I saw aluminum corrosion was when I spotted aluminum tubing sticking out of the ground at the house. It just made a pile of aluminum dust! I have no idea how a ground plane would work if the aluminum opened up in time in different places, so sticking with copper seems the best way to go. If I had a problem with radiation my mind would be pointing at the aluminum every time so why the hassle? You never know what state your ground is in these days because the builders spread building garbage aound before they spread the grass ! Now we have acid rain to think about. |
Aluminum as a ground system
Ed wrote:
I am only interested in the long term reliability of an aluminum ground system in comparison to the more common copper system. This is for lightning suppression only, I am not addressing RF issues. I am wondering if aluminum can handle the potential surge currents that copper can... and how well does its ground conductivity work when buried, when compared to copper. Ed K7AAT If you're talking lightning, you're talking RF! 73, Roger |
Aluminum as a ground system
If you're talking lightning, you're talking RF! 73, Roger Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed .. |
Aluminum as a ground system
"Ed" wrote in message . 192.196... If you're talking lightning, you're talking RF! 73, Roger Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed A lightning bolt is a transient so its current must be composed of components having a wide range frequencies. Consequently lightning conductors need small self-inductance as well as small resistance to work properly. Chris |
Aluminum as a ground system
"Ed" wrote in message . 192.196... If you're talking lightning, you're talking RF! 73, Roger Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? lightning has MANY frequencies from DC to many MHz. |
Aluminum as a ground system
Ed wrote:
Lightning is DC. How could it be " RF " if it has no "frequency" ? Fourier analysis of pulsed DC? -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Aluminum as a ground system
Ed wrote:
Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL |
Aluminum as a ground system
Roy Lewallen wrote in
: Ed wrote: Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL Indeed Roy, rather than argue that lightning doesn't contain AC components, one could more cogently argue that it is *not* DC. It is evident that many hams treat lighting as DC in the design of their lightning protection system (eg small conductor diameter, sharp bends, loops, u-turns etc in down conductors), but if you pick up the simplest models for analysing a lightning down conductor, they treat it as excited by a double ramp current, and the down conductor as an inducance. Such a model is not a DC model. Owen |
Aluminum as a ground system
In article ,
Owen Duffy wrote: Roy Lewallen wrote in : Ed wrote: Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL Indeed Roy, rather than argue that lightning doesn't contain AC components, one could more cogently argue that it is *not* DC. It is evident that many hams treat lighting as DC in the design of their lightning protection system (eg small conductor diameter, sharp bends, loops, u-turns etc in down conductors), but if you pick up the simplest models for analysing a lightning down conductor, they treat it as excited by a double ramp current, and the down conductor as an inducance. Such a model is not a DC model. Owen Lightning is pulsed dc. The pulse can be examined by fourier analysis, as every sophomore electrical engineering student knows, revealing that the lightning pulse is made up of a superposition of ac waves of many frequencies. One can get away with explaining some things about lightning using simple dc analysis but most of the interesting stuff requires ac analysis. And then there is the business of a nearby lightning strike raising the voltage of ground lines so that during the strike; they are no longer at ground potential. This requires ac analysis with impedances rather than resistances. |
Aluminum as a ground system
Dave wrote:
"Ed" wrote in message . 192.196... If you're talking lightning, you're talking RF! 73, Roger Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? lightning has MANY frequencies from DC to many MHz. DC to daylight in fact. Well, light at least. 8^) - 73 de Mike N3LI - |
Aluminum as a ground system
On Fri, 25 Sep 2009 09:28:46 -0400, Michael Coslo
wrote: lightning has MANY frequencies from DC to many MHz. DC to daylight in fact. Well, light at least. 8^) And all this radiation happens because of a severe lack of equilibrium. Art can't fool Mother Nature. 73's Richard Clark, KB7QHC |
Aluminum as a ground system
If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL I think we're arguing semantics on this. I spoke in pure terms... there is no argument that Lightning itself is a DC current. The fact that it is so short may bring the other RF issues to play, but that is not where my thoughts were when speaking on the DC issue.. Ed |
Aluminum as a ground system
In article . 196,
Ed wrote: If you're talking lightning, you're talking RF! 73, Roger Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed . Well, actually Lightning is a Pulse of DC, which causes ANY conductor that it reaches to "RING" which is then AC, as it dissipates... So, it has Both components..... |
Aluminum as a ground system
Ed wrote:
If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL I think we're arguing semantics on this. I spoke in pure terms... there is no argument that Lightning itself is a DC current. The fact that it is so short may bring the other RF issues to play, but that is not where my thoughts were when speaking on the DC issue.. Ed Semantics are important when the goal is communication. Lightning induces extreme currents in nearby conductors, and radiates strong fields covering a wide portion of the radio spectrum, both characteristics of its RF content. High voltage DC transmission lines, for example, don't. While you could correctly call lightning "pulsed DC", it's certainly not correct to say it "isn't RF". As other folks have pointed out, effective lightning protection requires a solid understanding of its RF nature. Roy Lewallen, W7EL |
Aluminum as a ground system
wrote in message ... In article , Owen Duffy wrote: Roy Lewallen wrote in : Ed wrote: Roger, Lightning is DC. How could it be " RF " if it has no "frequency" ? Ed If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL Indeed Roy, rather than argue that lightning doesn't contain AC components, one could more cogently argue that it is *not* DC. It is evident that many hams treat lighting as DC in the design of their lightning protection system (eg small conductor diameter, sharp bends, loops, u-turns etc in down conductors), but if you pick up the simplest models for analysing a lightning down conductor, they treat it as excited by a double ramp current, and the down conductor as an inducance. Such a model is not a DC model. Owen Lightning is pulsed dc. The pulse can be examined by fourier analysis, as every sophomore electrical engineering student knows, revealing that the lightning pulse is made up of a superposition of ac waves of many frequencies. One can get away with explaining some things about lightning using simple dc analysis but most of the interesting stuff requires ac analysis. And then there is the business of a nearby lightning strike raising the voltage of ground lines so that during the strike; they are no longer at ground potential. This requires ac analysis with impedances rather than resistances. .... and the mayhem that can ensue to wired services, such as telephone, when a structure at a transmitting station on a hill is struck! Chris |
Aluminum as a ground system
On 25 Sep 2009 17:09:06 GMT, Ed
wrote: I think we're arguing semantics on this. I spoke in pure terms... there is no argument that Lightning itself is a DC current. Only in the sense that for 100nS a 160M transmission is DC current. 73's Richard Clark, KB7QHC |
Aluminum as a ground system
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Aluminum as a ground system
Jeff Liebermann wrote in
: On 22 Sep 2009 23:19:40 GMT, Ed wrote: QUESTION: Are aluminum ground systems becoming common? Are they reliable, even after absorbing some heavy strikes? Any other comments? Ed K7AAT on the Oregon Coast I've never seen any that use aluminum wire. Everything I've seen and what little I've done was copper wire for both mountain top and home grounding. You can come to Florida where you'll find the lightning supression systems on the buildings here all use about a 1" aluminum rope to interconnect all the spikes and tie into the building ground. 73, Bruce |
Aluminum as a ground system
"Cecil Moore" wrote in message ... Ed wrote: Lightning is DC. How could it be " RF " if it has no "frequency" ? Fourier analysis of pulsed DC? Sorry, I swore of that stuff as soon as I passed the final. |
Aluminum as a ground system
"Ed" wrote in message . 192.196... If you're not convinced after reading the responses, turn on your radio the next time a lightning storm is anywhere nearby -- or for that matter, anywhere within skip propagation range. Then explain how it is your radio is hearing DC. Roy Lewallen, W7EL I think we're arguing semantics on this. I spoke in pure terms... there is no argument that Lightning itself is a DC current. The fact that it is so short may bring the other RF issues to play, but that is not where my thoughts were when speaking on the DC issue.. Ever hear that the lightning strike is an oscillating series of cloud-ground-cloud-ground currents? Sounds not too much like DC. Sal |
Aluminum as a ground system
Richard Clark wrote:
On Fri, 25 Sep 2009 09:28:46 -0400, Michael Coslo wrote: lightning has MANY frequencies from DC to many MHz. DC to daylight in fact. Well, light at least. 8^) And all this radiation happens because of a severe lack of equilibrium. Art can't fool Mother Nature. I once suffered a severe case of lack of equilibrium, probably related to an adolescent experiment with ethanol containing liquids. It left a lasting impression on me and I avoid the state with great prejudice. But since I have regained my equilibrium, my friends say that I am positively radiant! Perhaps our friend speaks sooth? - 73 de Mike N3LI - |
Aluminum as a ground system
On Mon, 28 Sep 2009 14:25:12 -0400, Michael Coslo
wrote: Perhaps our friend speaks sooth? All depends if sooth is an adjective or a noun. The OED (a notably gay English dictionary) offers "soothing, soft, smooth" 73's Richard Clark, KB7QHC |
Aluminum as a ground system
Richard Clark wrote:
On Mon, 28 Sep 2009 14:25:12 -0400, Michael Coslo wrote: Perhaps our friend speaks sooth? All depends if sooth is an adjective or a noun. The OED (a notably gay English dictionary) offers "soothing, soft, smooth" Well, fine, but I'm not sharing any hotel rooms... - 73 de Mike N3LI - |
Aluminum as a ground system
On Mon, 28 Sep 2009 14:34:38 -0400, Michael Coslo
wrote: Perhaps our friend speaks sooth? All depends if sooth is an adjective or a noun. The OED (a notably gay English dictionary) offers "soothing, soft, smooth" Well, fine, but I'm not sharing any hotel rooms... Not even the same Area Code. 73's Richard Clark, KB7QHC |
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