[TowerTalk] Grounding System Question

[Tony]

Jim:

> The position of the rods isn't  going to make a lot of difference in
 > how the current flows with respect to the house.

So the tower doesn't necessarily have to be concentric with the ground 
rods circling the tower?

> Is your tower on a foundation,  or planted on the bare dirt?

The crank up tower It's anchored to a concrete foundation that's about 7 
feet deep. The existing ground rods are about a foot away from the edge 
of the foundation.

> You can use strap if you find  it mechanically convenient, but from a
 > lightning impulse standpoint, round wire works just fine.

I'm glad to hear that because I already have some #2 solid and tinned 
copper wire.

Thanks Jim.

Tony



On 4/14/2014 9:15 PM, Jim Lux wrote:
> On 4/14/14, 5:48 PM, Tony wrote:
>> All:
>>
>> My crank-up tower is located a few feet from the house and each leg is
>> attached to a ground rod that's about a foot or so away from the
>> foundation.
>>
>> I'd like to add 3 more rods in a radial pattern to help "divert" a
>> potential lightning strike away from the house.
>
> The position of the rods isn't going to make a lot of difference in 
> how the current flows with respect to the house. Is your tower on a 
> foundation, or planted on the bare dirt? If it's bolted to a 
> foundation, that will probably be the dominant current path to the 
> surrounding soil, because it's got a lot of surface area in contact 
> with the soil.
>
>
> The grounds can't be
>> positioned 360 degrees around the tower due to it's close proximity to
>> the house so I'm not sure how critical that is.
>
> More important is the spacing of the rods from each other. Two rods 
> driven 6" apart is basically one rod.  Spacing them two rod lengths 
> apart is a good place to start. If you're worried about electrical 
> codes, 6 feet is the minimum spacing (of course, if you're driving 8 
> foot rods and you space them twice their length, then the 6 foot rule 
> is moot)
>
>
>>
>> Any suggestions on this subject as well as rod spacing and copper strap
>> size would be appreciated.
>>
>
> You can use strap if you find it mechanically convenient, but from a 
> lightning impulse standpoint, round wire works just fine.
>
> How big the wire has to be is more about mechanical ruggedness. AWG 6 
> is what the code requires, if you're stapling it to the house or 
> something, if it's hanging out #4.
>
> "A 4 AWG or larger copper or aluminum grounding electrode conductor 
> shall be protected where exposed to physical damage.
>
> A 6 AWG grounding electrode conductor that is free from exposure to 
> physical damage shall be permitted to be run along the surface of the 
> building construction without metal covering or protection where it is 
> securely fastened to the construction; otherwise, it shall be in rigid 
> metal conduit, intermediate metal conduit, rigid nonmetallic conduit, 
> electrical metallic tubing, or cable armor."
>
>
> You can get a bit wrapped around the axle/prop shaft if you start 
> trying to differentiate between the "grounding electrode conductor" 
> (the wire from service disconnect/feeder to the FIRST ground rod) and 
> "bonding jumpers" (a wire between grounded stuff, including a pair of 
> rods).
>
> It is ok by the code to do #4 from panel to first rod, then #6 from 
> there.
>
>
> A lot of lightning protection systems use #2 everywhere.  #2 is what's 
> required for a "ground ring" and if you're in the lightning protection 
> business, likely you've got a big spool of bare AWG2 on the truck, and 
> you just use it for everything.
>
>
>> Thanks
>>
>> Tony
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>