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Author Topic: Basement Ground Rods  (Read 2268 times)
KB1NO
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Posts: 15




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« on: October 17, 2007, 05:02:55 PM »

Shack is in a corner of the basement on the diagonally opposite corner of the house from the service entrance.   The (2) service entrance ground rods are in the basement directly below the electrical panel.  

My SPG ground rod is outside the shack where the antenna coax comes in.

I want to bond the service ground to the SPG ground
and was thinking of running #4 copper wire *inside* around the perimeter of the basement to the service entrance ground with 8' ground rods every 16'along the way.
My thought is that this is shorter and a better ground because the ground rods are buried 8' deeper than they would be outside.  

But the tradeoff is that lightning currents could be inside the basement.

Questions:
Does the deeper ground rod driven through the basement floor provide higher quality ground?

Or is it better to go outside, which means a longer run
and 12' coming into the house to get to the Service Panel ground rods.

Thanks,
John
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WB2WIK
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Posts: 20567




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« Reply #1 on: October 17, 2007, 05:26:47 PM »

You don't need to add more ground rods for the route the SPG connection takes to the service panel.

NEC calls for #8 Cu or #6 Al, and you can just run it any way you choose.  

The purpose of the SPG wire is to assure there isn't much differential between the two ground points.  You'll achieve that easily.

No matter what you do, you're never totally protected against a lightning hit.  *Insurance* is a very good thing for that.  Make sure your insurance covers the appreciated value of your construction including all contents and ham gear.

WB2WIK/6
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K9KJM
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« Reply #2 on: October 18, 2007, 12:44:05 AM »

It is a BAD idea to drive ground rods inside the house. A much better plan is to route that bonding cable outdoors and install your rods there.
Protection from direct lightning strikes IS very possible, And in fact is done at all commercial communications tower sites, Where the tall towers are hit most every large storm, With NO damage to equipment.
"Insurance" will NOT replace a human life if you are not properly protected.
#8 copper is really not large enough for decent lightning protection bonding.
Flat copper strap is the best, #2 or #4 copper is a distant second choice.
http://members.cox.net/pc-usa/station/ground3.htm
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KB9CRY
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« Reply #3 on: October 18, 2007, 06:15:34 AM »

But the tradeoff is that lightning currents could be inside the basement.

Not a tradeoff actually, this is THE reason to route it outside.


Questions:
Does the deeper ground rod driven through the basement floor provide higher quality ground?

No
 

Or is it better to go outside, which means a longer run
and 12' coming into the house to get to the Service Panel ground rods.

Yes, actually this is the only way.
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K1CJS
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Posts: 5997




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« Reply #4 on: October 19, 2007, 12:44:39 PM »

Ground rods for lightning protection purposes should be driven in to the earth outside your home.  If you do have an inside the basement ground rod, you've got to remember that it is an electrical service ground, not a lightning discharge ground.  For safety sake, if your home station were to be struck by lightning, YOU WOULD NOT WANT THAT KIND OF RAW ENERGY DIRECTED INSIDE YOUR HOME.

Now, for the question "Do you want your ground cable/strap run inside your house?", the answer would be you are just following the NEC regulations on grounding.  Whether through the basement or around the outside of the foundation doesn't make that much difference if the service ground is inside.  If you get hit, you get hit and the routing of the connecting cable isn't going to matter.

If you don't have an outside ground for your tower/mast and your station, install a grounding system outside your home for them.  And if you're that anxious about the extra six feet or so of ground rod depth, get the specialized ground rod that allows two or more rods to be connected together, and drive them in--OUTSIDE.
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KB1NO
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« Reply #5 on: October 21, 2007, 04:35:56 PM »

Thanks to all for your replies.
Considered your inputs and gave it more thought.
A #4 Bonding wire would connect two sets of ground rods separated by 50 feet. I think that
it is best to be outside as was suggested.
If there is a significant potential difference caused by a nearby lightning strike,  the wire could vaporize.

I'd rather that not happen in the basement.

vy 73,
John
KB1NO
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N2VPC
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Posts: 107




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« Reply #6 on: November 01, 2007, 06:19:44 PM »

If you do decide to drill holes in your basement floor make certain it is away from the outer wall enough as not to hit the footing/foundation.  Also try to identify where the underlying pipes are under the slab (water, sewer, drain, gas, etc.).
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