Table of Contents
Advertisement
4.1.1 Effect of Ground Electrode Size and Depth on
Resistance
Size: Increasing the diameter of the rod does not materially reduce its resistance.
Doubling the diameter reduces resistance by less than 10%.
100
Depth: As a ground rod is driven deeper into the earth, its resistance is
substantially reduced. In general, doubling the rod length reduces the resistance
by an additional 40%.
200
100
Digital Ground Resistance Tester Models 4620 & 4630
75
50
25
0
1/2
5/8
3/4
80
60
40
30
20
1" dia.
10
8
6
5
4
3
2
1
5
15
Driven Depth in Feet
Ground Resistance Versus Ground Rod Depth
1
1 1/4
Rod Diameter (inches)
Figure 4
1/2" dia.
25
35 40
Figure 5
1 1/2
1 3/4
50
60
70
23
Advertisement
Table of Contents
