Derek: I'm no expert on grounding, but I won't let that get in my way of offering advice. <g>
I have seen a lot of Illinois barns, and my first comment is, if it looks too good, it won't blend in with the landscape. (Obviously, by blending in, you mean matching the esthetics of the local level of development; you want this to look like a well-maintained older structure so as to not attract attention from people who fear you are installing a copper smelter. Obviously, there's no way that a big red barn is going to blend in with the green trees or snow.) OK, so you have built a nice, big metallic target (I mean a building) that sticks up above the trees. Yes, you will attract lightning. You don't want those lightning strokes to attach just anywhere on your target, since the metal sheathing is not going to handle those thousands of amps very well. I would expect considerable attachment point erosion and lots of arcing along whatever path the current ultimately takes. I would head this off by installing a welded structural bean along the crest of your target, with a few vertical posts (lightning rods) sticking up maybe 2 meters or so. I would drop a vertical structural steel piece, at each end of the target, down to ground rods. Remembering that the Illinois frost line is about 40", I would get a nice hunk of scrap steel (like an old 20' section of railroad rail) and get an auger and drill a nice hole for the ground rods. Then, I would weld the ground rod to the vertical piece. Maybe you could use those existing vertical columns you said you had at each end of the building, but you would want to be sure they were hefty conductors, and that every joint was welded. I don't think you need to use anything like a copper grounding system. As for grounding the power feed, I suppose you could bond it to one of those big ground rods. But first, you need to describe you power service feed. Sure, lot's of overkill, but with every joint welded, and the conductors massive, you won't have to rework anything in your lifetime. Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty > -----Original Message----- > From: [email protected] [mailto:[email protected]] On Behalf > Of Derek Walton > Sent: Sunday, August 30, 2009 10:57 AM > To: IEEE EMC Discussion Group > Subject: Thoughts and opinions sought > > Morning all, > > I'm pondering which path to follow with a grounding issue. > I'm not so much concerned with code requirements, I see these > as the minimum, I'm after best... > > First some background. I have built a building to house my business. > I've located this well in the boonies on some 23 acres of > woods. In order to blend in it's in the shape of a classic > Midwest USA barn. It was custom engineered from Steel > red-iron and Steel siding. > > My quandary is how best to ground this for electrical safety > and lightning. It's a fairly large building ( 50 feet by 80 > feet ) and reaches almost to the tops of surrounding trees. > Terrain wise we seem to have a fair number of strikes, in the > last 5 years we have lost 3 trees to lightning. > > If I follow guidance I have been given to ground the building > only where the power enters, I see this as a week point > during a lightning event. > > A bit more about the building. If you can imagine 5 huge > horseshoes stood upright on the open end, thats what the main > frame looks like. > There is of course a large amount of interconnecting red iron > and two additional vertical columns at each end of the > building. Over the whole frame is steel siding. The whole > thing is bolted together with many 1 inch and 1/2 inch bolts. > The siding has close to 8000 screws fastening it to red iron. > > The building stands right now about 1 foot above "dirt" on a > concrete footing wall, and there is a 10 foot wide concrete > path to be installed all around the building making up the 1 > foot height difference: the solution to my quandary is needed > before the concrete can be installed. > Soon would be nice so I can quit getting muddy boots :-) > > I'm leaning towards installing a copper grounding ring all > around the building say 4 to 5 feet or maybe up to 10 feet > away from the footing wall. This ring will be about a foot > down in the dirt. At the point where each building column > touches the concrete I'm looking to install a heavy ( 4/0 ) > grounding wire out to the wire ring. At the point they meet > I'll drive a 10 foot grounding rod flush with the wire ring > and join them with exothermic welds. 4/0 wire is easy to get > here, but copper strips may also be an option. > > I'm looking for thoughts, opinion, recommendations on whether > this approach is sound, sufficient, overkill, under kill etc. > Both I, and my boots, would appreciate the groups thoughts. > > Sincerely, > > Derek Walton > L F Research > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. 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