"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.