Derek:
You paint a good picture but you leave out some critical details.
1. Is electrical noise an issue to your business? i.e. do you make low
level
electrical measurements?
2. What is your height above the average plane? (This will have a lot to do
with lightning susceptibility.)
3. What is your soil like? Drainage?
4. Are the metal parts of the building bonded? Did you use grounding type
hardware or the screws with rubber washers for the sheeting?
5. Any galvanize in the structure?
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6. Do you have high power noise generators, like a water well pump?
7. What kind of trees? Are you going to protect the trees or are the trees
going to protect you? (Not all woods are created equal)
8. Is your electrical service above ground?
All situations are unique so it's hard to generalize. I strongly advise you
get a soils engineer to help you design your grounding system. He needs to be
a local one that knows your area.
Fred Townsend
DC to Light
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
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