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ETL 1110-9-10(FR)
5 Jan 91
5)
Determine the total circuit resistance (RT), from
equation 1-3:
RT = RN + RW + RC
Where:
RN =
Anode-to-water resistance
RW =
Wire resistance
RC =
Tank-to-water resistance.
a)
step 4 above. (RN = RA since RA is equal to one
continuous wire anode).
b)
Header cable/wire resistance (RW) is solved using
equation 1-15:
LW RMFT
RW '
1000 ft
Where:
LW = 115 ft (Effective wire length. The
positive wires from the rectifier
to each end of the anode circle
will be approximately 115 ft long)
RMFT =
0.51 ohm (Effective wire resistance
per 1000 lin ft. Since there are
positive wires from the rectifier
to each end of the anode circle,
each wire will carry about one half
of the current [12.5
amp].
The
wires selected are No. 10 AWG.
Because the two wires are in
parallel, the effective resistance
is
one half the single wire
resistance [1.02 ohms per 1000 lin
ft/2 = 0.51 ohm])
RW
=
115 ft x 0.51 ohm
1000 ft
RW
=
0.06 ohm
c)
Tank-to-water
resistance
(RC)
and
negative
circuit resistance.
The negative wire is connected to the tank
structure near the rectifier, so its resistance
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