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ETL 1110-9-10(FR)
5 Jan 91
Weight is not a factor in supporting the string.
15) Calculate the anode-to-water resistance of a single
anode rod (RA), using equation 2-8:
0.0052 p 1n(D/DA)
RA '
(eq 2-8)
LB
Where:
p =
4000 ohm-cm (Water resistivity from
item 3 of paragraph 2-7a)
D=
5 ft (Riser diameter from item 2 of
paragraph 2-7a)
DA =
0.0115 ft (0.138 in) (Diameter of
anode rod from item 6 of paragraph
2-7a)
LB =
112 ft
(Length of anode rod from
previous discussion)
RA =
0.0052 x 4000 x 1n (5./0.0115)
112
RA =
1.13 ohms
riser anode, from equation 1-12:
RT = RA + RW + RC
Where:
RA =
Anode-to-water
resistance
of
a
single anode rod.
RW =
Wire resistance.
RC =
Tank-to-water resistance.
a)
step 15 of paragraph 2-7b.
b)
Header cable/wire resistance (RN) from equation
1-15:
98
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