2.2.1.6
Automatic Cathodic Protection Control
The system shall be capable of maintaining a tank-to-water potential
criterion of protection within plus or minus 25 millivolts regardless of
changes in water chemistry, temperature, or water level in the tank.
Provision shall be made for readily changing the range and limits of the
criterion. The controller shall be either housed integrally with the
rectifier or in a separate weatherproof cabinet with provisions for
locking. The automatic controller shall be a completely solid-state
design, and shall be capable of automatically maintaining the tank-to-water
potential at minus 900 millivolts with respect to a copper-copper sulfate
reference electrode within an accuracy of 25 millivolts. The tank-to-water
potential measured and maintained by the controller shall be free of "IR"
drop error.
2.2.1.7
Tank To Water Potential Meter
The controller shall be equipped with a calibrated voltmeter having an
internal impedance exceeding 1 megohm which shall be so connected to read,
from the system reference cell, the tank-to-water potential being
maintained by the cathodic protection system. This voltage reading shall
be free of "IR" drop error.
2.2.2
Cabinet
Cabinet shall be constructed of [not lighter than 1.56 mm No. 16 gauge
[steel] [hot dipped galvanized steel] [stainless steel] [aluminum]] [molded
fiberglass reinforced polyester], and shall be provided with a full door.
The enclosure shall have oil-resistant gasket. The door shall be hinged
and have a hasp that will permit the use of a padlock. The cabinet shall
be fitted with screened openings of the proper size to provide for adequate
cooling. Holes, conduit knockouts, or threaded hubs of sufficient size and
number shall be conveniently located.
2.2.2.1
A complete wiring diagram of the power unit showing both the ac supply and
the dc connections to anodes shall be on the inside of the cabinet door.
All components shall be shown and labeled.
2.2.2.2
Grounding
Grounding provisions shall [be as specified in Section 16402 INTERIOR
DISTRIBUTION SYSTEM.] [comply with NFPA 70 and UL 467 including a ground
terminal in the cabinet.] The grounding conductor from the terminal to the
earth grounding system shall be solid or stranded copper not smaller than
No. 6 AWG. The earth grounding system shall consist of one or more rods.
Ground rods shall be [copper-clad steel conforming to UL 467] [zinc-coated
steel conforming to ANSI C135.30] [solid stainless steel] not less than
[16] [19] mm [5/8] [3/4] inch in diameter by [2.4] [3.1] m [8] [10] feet in
length. Rods shall be driven full length into the earth. Sectional type
rods may be used.
2.2.2.3
Resistance to Ground
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NOTE: Remove this pagagraph if not required in the
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SECTION 13111A
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