ETL 1110-9-10(FR)

5 Jan 91

H=

12 ft (Anode depth below water

surface)

Anode

depth

has

been

determined

from

the

following

calculations:

The distance from the bottom of the tank to the anode

wire circle should be about 40 percent of the water

depth.

Water depth

=

20 ft from item 3 of paragraph

2-8a.

20 ft x 40% = 8 ft

Anode depth below water surface (H):

H = 20 ft - 8 ft = 12 ft

Calculate RA:

RA

= 0.0016 x 2000 [in 8 x 27.5 + in 2 x 27.5]

27.5

0.0052

12

RA

= 0.1164 [ln 42,307.7 + ln 4.6]

RA

= 0.1164 [10.65 + 1.531

RA

= 1.42 ohm

At a current requirement of 12 amp, voltage required

for this resistance, from Ohm's Law is:

E

= I x RA

E

= 12 x 1.42 = 17.2 V

This is a reasonable voltage, so the resistance of

1.42 ohms is acceptable.

6)

Determine the total circuit resistance (RT), from

equation 1-3:

RT = RN + RW + RC

Where:

RW = Header cable/wire resistance.

RC = Tank-to-water resistance.

108

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