I need advice in placing grounding rods when upgrading electrical service
from 100 amp to 200 amp.

Code requires at least 2 5/8" x 8' rods placed no closer than 6'.

Soil conditions: sandy loam. Water table is about 15-18' below grade.

I am considering stacking rods so I will end up with 2 16' rods.

Question is how close can these be without compromising effectiveness of
grounding system?

"franz frippl" wrote in message
news
I need advice in placing grounding rods when upgrading electrical service
from 100 amp to 200 amp.

Code requires at least 2 5/8" x 8' rods placed no closer than 6'.

Soil conditions: sandy loam. Water table is about 15-18' below grade.

I am considering stacking rods so I will end up with 2 16' rods.

Question is how close can these be without compromising effectiveness of
grounding system?


No less than 6'. There are rods made that have the ends threaded to add
length. I think that they are available from McMaster-Carr;
http://www.mcmaster.com

You can also buy 3/4" x 10' ground rods at some electrical supply companies.

As another posted stated a distance of 16' or more from each other is
optimal for 8' rods. If the rods are longer they should be further apart.
If you are very concerned about soil resistively you could always install 3
or 4 rods.

"franz frippl" wrote in message
news
I need advice in placing grounding rods when upgrading electrical service
from 100 amp to 200 amp.

Code requires at least 2 5/8" x 8' rods placed no closer than 6'.

Soil conditions: sandy loam. Water table is about 15-18' below grade.

I am considering stacking rods so I will end up with 2 16' rods.

Question is how close can these be without compromising effectiveness of
grounding system?

You may want to try stacking two 3/4" x 10' instead as previously
suggested. Hard to tell best placement with just two locations as soil
resistivity varies so much from just a few feet away and from time to time.
For sandy loam, best to install couple of ground wells and keep rods wet
year around.

If you have access to the foundation rebar(continuous 20' with no vapor
barrier) known a Ufer ground, its better than ground rods.

I am considering stacking rods so I will end up with 2 16' rods.

Why don't you just drive another 8' rod (IAW code) and be done with it.
You will be perfectly legal. If the earth doesn't really conduct
electricity then your "perfect groups" to the water table will not make any
difference.


Question is how close can these be without compromising effectiveness of
grounding system?

What are you trying to protect yourself against? Why sort of fault or
event will your "perfect" ground protect you against? The only thing I can
think of is if your "service neutral" opens. In that case, your ground
system could get charged (depending upon what is on and what is off in your
home) with up to 120 volts. But since your soil is a good insulator, it
really would not make any difference.