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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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