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ETL 1110-9-10(FR)
5 Jan 91
=
Average anode lead wire length/
number of anodes. This is based
on the circuit resistance for 6
anode lead wires in parallel.
RMFT
=
2.58 ohms - Resistance for No.
14 AWG cable which has been
selected from table A-6.
RW
=
15 ft x 2.58 ohms
1000 ft
RW
=
0.039 ohms
c)
RS
Rc '
A
Where:
RS
=
2500 ohm-sq ft - Effective
coating resistance from item 8
of paragraph 2-2a.
A
=
11,791
sq
ft
-
External
pipe surface area calculated in
step 1 of paragraph 2-2b.
RC
=
2500 ohm-sq ft
11,791 sq ft
RC
=
0.212 ohm
d)
Calculate the
total
circuit
resistance
(RT)
from
equation 1-3:
RT
=
RN + RW + RC
RT
=
1.67 + 0.039 + 0.212
RT
=
1.921 ohms
e)
Since the design requirements call for a maximum
1.921 ohms, the design using six (3-in x 5-ft) ceramic
anode canisters will work.
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