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ETL 1110-9-10(FR)
5 Jan 91
VREC = (I) (RT) (120%)
Where:
I
=
12 amp (Current requirement from
step 3)
RT
=
1.5 ohms (Total circuit resistance
from previous calculation)
120%
=
Rectifier voltage capacity design
safety factor.
VREC
=
12 amp x 1.5 ohms x 1.2
VREC
=
21.6 V
c.
Select rectifier.
Based on the design requirements of 21.6 V and 12 amp, a
commercially available 24-V 16-amp unit is selected.
d.
Automatic potential control.
To prevent over- or under-protection as the water level
varies, automatic potential control is specified. The tank
and riser to water potential is maintained by the
controller
through
permanent
copper-copper
sulfate
reference electrodes suspended with the bowl and riser. The
reference electrodes should have a design life of at least
15 years.
The automatic controller is located in the rectifier unit.
The controller must be capable of sensing the potential
accurately and must be free of IR (voltage) drop error.
The controller does this by turning off the rectifier for
a fraction of a second, during which time the tank-to-water
potential is measured. The measurement is then compared
with a present standard
and the output adjusted
accordingly.
e.
Installation details.
Figures 2-22 and 2-23 show typical details.
f.
Loop anode attachment guidelines.
110
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