Your building needs two things: - a good lightning protection system (you know, with lightning rods). - a good electrical system. >From what I have seen, you are trying to make your building lightning protected by building a good electrical system.
I have no confidence in my ability to design lightning protection and have not seen any comments or replies yet which properly address it. It will not rely on siding or screws, etc. Trust a good contractor to install a good (UL Listed - they actually approve the building) lightning protection system. The standards for lightning protection (not meaning the electrical code) have been well thought through and will do a good job. As part of this they will install proper earth electrodes and building bonding. The electrical system grounding is meant to provide an equipotential environment which will handle system ground faults and shock risk. As part of that equipotential setting, the bonding to the building and to the lightning ground path is described in the code. The code goes to great lengths to assure this equipotential environment. The dirt connections assures you don't get into trouble when you stand outside in the wet dirt and touch the metal building. The ground electrodes have essentially nothing to do with the interior environment. I think the reason you are feeling unsure is that you have been trying to use the electrical code for lightning protection. It was not designed for that and your guesses at improvements will at best be uncertain and likely inadequate. Bob Johnson ITE Safety <http://www.itesafety.com> Derek Walton wrote: 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]> <mailto:[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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