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  1. #1
    Platinum Member mx842's Avatar
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    Default Lightning protection....

    I put this big beam up on 4 steel post and cross members in my shop to run a trolley on for a 1/2 ton chain fall. I also want to run some heavy ground wire under the floor that comes up in places all over the shop so I will have a ground leg for my welders no matter where the work is located.

    I don't know but it just seems to me that there seems like all this steel and ground wires running all over the place would be a prime target for a lightning strike. I am on a somewhat high spot with regard to the rest of the surrounding area anyway and we get at least one maybe two trees hit a summer on average within a 300' radius of the house and one hit a tree right next to the house and it bounced off and hit the corner of the roof and knocked off a few shingles and burned a cool little hole in the roof.

    The building I used to be in was a large steel building with medal sides and I don't know how many thunderstorms we had while I was there we never got hit but I was thinking it may be a good idea to at least think about lightning protection while I am still in the building stage.

    Can someone school me on lightning protection and what can be done to keep the risk of lightning strikes to a minimum and to be safe while inside in case one did hit the building or steel structure that is inside?

  2. #2
    Elite Member SPIKER's Avatar
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    Default Re: Lightning protection....

    Quote Originally Posted by mx842 View Post
    I put this big beam up on 4 steel post and cross members in my shop to run a trolley on for a 1/2 ton chain fall. I also want to run some heavy ground wire under the floor that comes up in places all over the shop so I will have a ground leg for my welders no matter where the work is located.

    I don't know but it just seems to me that there seems like all this steel and ground wires running all over the place would be a prime target for a lightning strike. I am on a somewhat high spot with regard to the rest of the surrounding area anyway and we get at least one maybe two trees hit a summer on average within a 300' radius of the house and one hit a tree right next to the house and it bounced off and hit the corner of the roof and knocked off a few shingles and burned a cool little hole in the roof.

    The building I used to be in was a large steel building with medal sides and I don't know how many thunderstorms we had while I was there we never got hit but I was thinking it may be a good idea to at least think about lightning protection while I am still in the building stage.

    Can someone school me on lightning protection and what can be done to keep the risk of lightning strikes to a minimum and to be safe while inside in case one did hit the building or steel structure that is inside?

    It will go where it wants to, but to control lighting somewhat you need to have a cage around you. So you have the grounds in the slab which is fine for the welder but you dont want to let lighting in there as the heating caused could blow out the concrete. when I say heating if hit directly the heavy cable will pretty much vaporize and in doing so expand in size a few hundred times almost instantly. however not very likely.

    anyhow you would need some good deep ground rods out away form the sides at the corners or along the sides and then a cable/bar system running the roof and out and down the corners that will have heavy cable directing it down into the rods.

    the ground rods should be tied in a loop around the perimeter for pest results.

    general rule of thumb any longer adding all the extra lighting protection can actually attract the lighting to the building or area of the building...

    Best bet is to keep the electrical system well grounded and the well cabling isolated from other parts where if hit the well becomes the best ground around.

    Mark
    I may remember why I went to the other end of the shop, I'm just afraid once I get there I'll forget how to get back!

  3. #3
    Veteran Member Raspy's Avatar
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    Default Re: Lightning protection....

    I have a similar situation and I've decided to do something about it too.

    My house is a 60X60 steel truss building on a concrete foundation. I have rebar running both ways on 12" centers and the bolts for the posts go down at least 24" below grade and are welded to the footing rebar.

    This is built better than the standard Ufer ground system for the electrical system.

    I'm at 5000' in Nevada and there are lightening strikes that start fires every year.

    My solution is to put four 3/4" copper clad ground rods sticking up three feet above the roof, along the ridge. These come down through roof jacks and clamp to the steel trusses that bolt to the posts that bolt to the foundation.

    This is intended to ground the potential before there is a lightening strike. It's pretty common technology, simplified and made practical in a steel building. Most lightening rods are connected to ground rods driven in at both ends of the house, but my system will carry vastly more amps to ground and should protect the house nicely. It will also be tied to the solar collector array. There will also be a large conductor bolted to one steel post and clamped to the electrical Ufer ground at the main service entry. And finally, I plan to have another conductor connected from the well casing (6" steel pipe, 320' deep) to the service ground and to bond the oil tanks to the whole system.

    That should do it. But remember, as the potential builds up in the atmosphere, before a lightening strike, my understanding is that it can be conducted to ground and a strike avoided. If there is a strike, at least I've done the best I can to ground it safely. The conducting path should be low resistance and carefully built. Some considerations are clean connections, unpainted lightening rods and gradual bends on the rods. Another debate rages about the ends of the rods. It was thought originally that they should be sharply pointed, but more recent tests suggest a blunt, rounded, dull point is better. Seems like copper clad electrical ground rods are almost perfect and I plan to tin the ends of mine, where the steel is exposed, with solder as rust protection and as a good conductor.

    It's fun project, and really easy with a steel building and steel trusses. As far as I'm concerned it's well worth the effort.

    One old trick around boats is to dangle the anchor chain overboard and connect it to the mast with jumper cables. A friend of mine was in Panama and a strike melted his anchor windlass! Sheesh. He didn't have it set up as I described, just sitting there and BAM!
    Last edited by Raspy; 02-24-2012 at 11:25 AM.
    John

    I only exaggerate enough to compensate for being taken with a grain of salt.

  4. #4
    Elite Member jonyyuma's Avatar
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    Default Re: Lightning protection....

    Raspy, Actually you need to clamp a large conductor to the rods all along the ridge and then down to independant ground rods in the ground. The steel building will have resistance, if you cannot afford copper wire then use aluminum. I am not a contractor for lightning, but have inspected a lot of systems on commercial buildings....Aluminum was used on many house units, installed when copper was expensive years ago. The short rods-18in to 2 foot are pointed , some are steel and others copper or aluminum, but plated..I believe your ground rod as a lightning rod idea will work as they are plated..
    Okay, Legal disclaimer: Old but not senile, definitely do not have the answer to everything!

  5. #5
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    Default Re: Lightning protection....

    Do other homes in the area have any lightning protection ?
    ::Sent from a standard desktop keyboard::

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  6. #6
    Veteran Member Raspy's Avatar
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    Default Re: Lightning protection....

    jony,

    While it seems true that I could get less resistance to the grounding system with a copper conductor, I could never get more amperage to ground with ground rods. In fact not even close. A Ufer ground has less resistance and far greater ampacity to ground than a ground rod does. If a strike does hit the system I have posts made of 8" H beams with 1/2" wall thickness, bolted to a large array of steel bar embedded in concrete that is buried in the ground as the foundation. These posts can carry far more amperage than a large copper wire. So it might be a good idea to have a copper conductor for the low voltage "draining" of the atmospheric potential, but not a strike.

    Until I studied Ufer grounding I thought it would be high resistance, but it turns out to be better than a normal ground rod. My "soil" is decomposing granite and has limited contact area with ground rods, plus the rods have a small surface area. They seem OK, generally, for a low voltage short but not much for lightening. It's just that most foundations are not set up as Ufer grounds and ground rods can always be added to an existing house. But if it's planned from the beginning, it can be done better.
    John

    I only exaggerate enough to compensate for being taken with a grain of salt.

  7. #7
    Veteran Member Raspy's Avatar
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    Default Re: Lightning protection....

    mx,

    I'm interested in how you could tie your welding grounds to the shop electrical ground and to the structure to get main service grounding, welding ground, and lightening grounds all in one. Could you? My system is as described above and I've been thinking about doing some welding on the structure by grounding the welder, in the garage, to a post and then welding on the other side of the house by simply taking the stinger and hot lead over there.

    For reverse polarity (positive ground) it might only work for welding if it was isolated from the house ground.

    When I was on a ship in the Coast Guard, we had a welder in the DC shop back near the fantail. It was grounded right there and we could weld anywhere on the ship with a single conductor. It was a steel 311 foot ship!
    John

    I only exaggerate enough to compensate for being taken with a grain of salt.

  8. #8
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    Default Re: Lightning protection....

    I think it was Lee Trevino who said the best lightening protection was to walk out in the open holding a 1 iron over your head. Because not even God can hit a 1 iron! Just a thought!

  9. #9
    Platinum Member mx842's Avatar
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    Default Re: Lightning protection....

    Quote Originally Posted by Raspy View Post
    mx,

    I'm interested in how you could tie your welding grounds to the shop electrical ground and to the structure to get main service grounding, welding ground, and lightening grounds all in one. Could you? My system is as described above and I've been thinking about doing some welding on the structure by grounding the welder, in the garage, to a post and then welding on the other side of the house by simply taking the stinger and hot lead over there.

    For reverse polarity (positive ground) it might only work for welding if it was isolated from the house ground.

    When I was on a ship in the Coast Guard, we had a welder in the DC shop back near the fantail. It was grounded right there and we could weld anywhere on the ship with a single conductor. It was a steel 311 foot ship!

    The welder is already tied to the building ground through the wiring that feeds it. I am putting 200 amp service in my building and from what I understand that requires two ground rods to be installed not more than 6 feet apart at the service entrance point. I plan to tie into these ground rods with a heavy copper wire to a second set of ground rods on the other side of the building where my welding room is going to be. I have one fixed welding table that will never move and I am running a ground wire in conduit to that table. I also have a rolling 4000lb lift table with a 11/4" aluminum top that I weld on and use as a setup and fixture table. This table is nice because I can position it anywhere needed when I have to weld long heavy pieces of material. I have several pieces of flat bar that is threaded so I can lay it out on to the floor to reach this table where ever it is. They lay nice an flat so you don't trip on them and you can still roll a cart over them and they don't get all tangled up like a long welding cable does.

    You have a good thought on grounding the structure post. I had thought about that but since lightning starts at the ground I was thinking that would be like painting a target on the building. While I am laying conduit I may run a ground wire to each post and tie everything in together since they are on piers it may be a good idea to do just that then I'll have ground points in the back of the building too.

    I don't see any reason you couldn't do the same thing with your setup as long as it is all welded together and not bolted. If it is bolted together you may not get good connections at some of the bolted sections and that may be a good spot to cause a fire.

    Also there is another safety factor, you may consider if you or any of the folks in your home has any electronic gadgets implanted in their bodies that is keeping them alive and that is the EMF that welding causes. This could have an adverse effect on these tiny devices if they are in the house while you are welding.

  10. #10
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    Default Re: Lightning protection....

    You just saved me the trouble of reposting.


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