Calculate the total circuit resistance (RT). cont'd

ETL 1110-9-10(FR)
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ETL 1110-9-10(FR)

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:

p FADJ

RN '

(eq 1-10)

398

where RN is the anode-to-electrolyte resistance in ohms, p

is the electrolyte resistivity in ohm-cm and FADJ is

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

expression may be used:

p PF

RN '

(eq 1-11)

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

groundbed anodes.

For multiple horizontal anodes:

p FADJ

RN '

(eq 1-12)

441

where p is the electrolyte resistivity in ohm-cm and FADJ is

an adj3sting factor for groups of anodes selected from

table 3-9.

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