[Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
I'm going to disagree with the following posting: If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. I have read Ericsson specs for cellular tower installation in that disagrees with the previous statement. Standard concrete without conductive enhancing materials can crack, pop or crumble if subjected to a direct lightning strike if ground rods are not properly installed. The water contained within the concrete will vaporize instantly causing the concrete to fail. There are types of conductive concrete mixes or additives that can be used, but the most common practice is to use a ground rod from each leg with a copper wire bonded to each tower leg. Our mfg building at work is made from steel I-Beams into concrete. I have noticed each I-Beam has its own ground connection. The strap is bolted to the beam about 1 above the concrete, then disappears into the concrete, and suspect there is a ground rod going into the soil beneath the concrete piling, but that's just a theory, as I dident see it before the mud was poured. Ed N3SDO
Re: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
I would suggest anyone interested in this subject should Google Ufer ground and get the real facts on the subject. The key to the concrete encased ground electrode is a properly installed rebar reinforcing in the concrete base. Burt VE2BMQ Ed Bathgate wrote: I'm going to disagree with the following posting: If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. I have read Ericsson specs for cellular tower installation in that disagrees with the previous statement. Standard concrete without conductive enhancing materials can crack, pop or crumble if subjected to a direct lightning strike if ground rods are not properly installed. The water contained within the concrete will vaporize instantly causing the concrete to fail. There are types of conductive concrete mixes or additives that can be used, but the most common practice is to use a ground rod from each leg with a copper wire bonded to each tower leg. Our mfg building at work is made from steel I-Beams into concrete. I have noticed each I-Beam has its own ground connection. The strap is bolted to the beam about 1 above the concrete, then disappears into the concrete, and suspect there is a ground rod going into the soil beneath the concrete piling, but that’s just a theory, as I dident see it before the mud was poured. Ed N3SDO Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:repeater-builder-dig...@yahoogroups.com mailto:repeater-builder-fullfeatu...@yahoogroups.com * To unsubscribe from this group, send an email to: repeater-builder-unsubscr...@yahoogroups.com * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
Please take note that there is a difference between grounding an electrical system, and grounding for lightning. The two situations are quite different. For designing and installing a lightning protection system see NFPA 780-250. The NEC (NFPA 70) does not address lighting protection other than when it is installed beside an electrical system ground. I am a certified electrical inspector (ICC) and electrical contractor (NM CA). In the southwest lightning protection is a BIG thing! Wes ARRL Technical Specialist AE6ZM VE7ELE Lincoln, CA CM98iv Placer County ARES
RE: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
Actually galvanized and copper plated ground rods should not be mixed in any ground system. Electrolysis will deplete the plating. All ground rods in any ground system are electrically connected to one another. 73 Gary k4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Glenn Little WB4UIV Sent: Tuesday, June 30, 2009 7:53 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode Another way to pass a ground cable through concrete is via a PVC pipe. The last thing that you want to do is run a ground cable that can carry lightning fault current through concrete without isolating the cable from the concrete. The fault current will rapidly heat the ground cable, causing it to expand, at the same time vaporizing the water trapped in the concrete. The result is a violent steam explosion. The results could be the total fragmentation of the concrete. MIL HDBK 419 is available for download. This is a military manual that addresses grounding. Another very respected guide is Motorola R-56. Galvanized ground rods should only be used at the guy anchor points. Copper plated ground rods should be used around the tower base and the building with all bonded together by exothermic welds 18 inches below grade. Ground rods are to be placed no closer than twice the length of the rod. Any closer and you are wasting your funds. YMMV. 73 Glenn WB4UIV At 10:07 AM 6/30/2009, you wrote: I'm going to disagree with the following posting: If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. I have read Ericsson specs for cellular tower installation in that disagrees with the previous statement. Standard concrete without conductive enhancing materials can crack, pop or crumble if subjected to a direct lightning strike if ground rods are not properly installed. The water contained within the concrete will vaporize instantly causing the concrete to fail. There are types of conductive concrete mixes or additives that can be used, but the most common practice is to use a ground rod from each leg with a copper wire bonded to each tower leg. Our mfg building at work is made from steel I-Beams into concrete. I have noticed each I-Beam has its own ground connection. The strap is bolted to the beam about 1 above the concrete, then disappears into the concrete, and suspect there is a ground rod going into the soil beneath the concrete piling, but thats just a theory, as I dident see it before the mud was poured. Ed N3SDO
RE: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode
Normally when grounding electrical and stakes we drive the rrod , connect the ground strap having sanded the connection and clamp securely then spray with a special metalic paint , been doing this a long time with good success. To: Repeater-Builder@yahoogroups.com From: gascha...@comcast.net Date: Tue, 30 Jun 2009 23:23:43 -0500 Subject: RE: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode Actually galvanized and copper plated ground rods should not be mixed in any ground system. Electrolysis will deplete the plating. All ground rods in any ground system are electrically connected to one another. 73 Gary k4FMX From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Glenn Little WB4UIV Sent: Tuesday, June 30, 2009 7:53 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: DC Ground Lightning Protection / Concrete Electrode Another way to pass a ground cable through concrete is via a PVC pipe. The last thing that you want to do is run a ground cable that can carry lightning fault current through concrete without isolating the cable from the concrete. The fault current will rapidly heat the ground cable, causing it to expand, at the same time vaporizing the water trapped in the concrete. The result is a violent steam explosion. The results could be the total fragmentation of the concrete. MIL HDBK 419 is available for download. This is a military manual that addresses grounding. Another very respected guide is Motorola R-56. Galvanized ground rods should only be used at the guy anchor points. Copper plated ground rods should be used around the tower base and the building with all bonded together by exothermic welds 18 inches below grade. Ground rods are to be placed no closer than twice the length of the rod. Any closer and you are wasting your funds. YMMV. 73 Glenn WB4UIV At 10:07 AM 6/30/2009, you wrote: I'm going to disagree with the following posting: If the tower is bolted to galvanized pipe that is embedded in concrete of which a significant amount is in contact with soil, you have a concrete-encased grounding electrode which is hard to improve upon. It is not likely that a ground rod would be worthwhile, since damp concrete (concrete in intimate contact with soil at grade level) is a fairly good conductor, and such a footing or foundation has hundreds of times the surface area of a ground rod. I have read Ericsson specs for cellular tower installation in that disagrees with the previous statement. Standard concrete without conductive enhancing materials can crack, pop or crumble if subjected to a direct lightning strike if ground rods are not properly installed. The water contained within the concrete will vaporize instantly causing the concrete to fail. There are types of conductive concrete mixes or additives that can be used, but the most common practice is to use a ground rod from each leg with a copper wire bonded to each tower leg. Our mfg building at work is made from steel I-Beams into concrete. I have noticed each I-Beam has its own ground connection. The strap is bolted to the beam about 1 above the concrete, then disappears into the concrete, and suspect there is a ground rod going into the soil beneath the concrete piling, but thats just a theory, as I dident see it before the mud was poured. Ed N3SDO _ Get the latest news, goss and sport Make ninemsn your homepage! http://windowslive.ninemsn.com.au/article.aspx?id=813730
