5 Jan 91
For optimum results, the length of the backfill column (L)
should be less than the anode spacing (Cc).
If multiple anodes are assumed to be 6 in. in diameter and
8 ft long, the following empirical expression may be used:
where RN is the anode-to-electrolyte resistance in ohms, p
selected from table 3-9, which compensates both for the
number and spacing of the anodes, which will be connected
together as one groundbed.
If the anode dimensions are different, another empirical
where RN is the anode-to-electrolyte resistance, RA is the
anode-to-electrolyte resistance for a single anode, p is
the soil resistivity in ohm-cm, N is the number of anodes
used, PF is a paralleling factor selected from table 3-5,
and Cc is the center-to-center spacing of anodes in feet.
This equation assumes a linear configuration of the
For multiple horizontal anodes:
where p is the electrolyte resistivity in ohm-cm and FADJ is
an adj3sting factor for groups of anodes selected from
For a circle of rod anodes (as in a water storage tank):
where RN is the anode-to-electrolyte resistance, p is the
electrolyte resistivity in ohm-cm, LB is the length of each