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The system shall include enclosure; main and branch circuit breakers;
starters, contactors, and reset buttons; selector switches, push buttons,
and pilot lights; circuit control items for electrical control of the
various plant components; and all necessary wiring and tubing. Electrical
control system shall be in accordance with NEMA ICS 1. Design, fabrication
and installation of all electrical components shall be in accordance with
requirements of NFPA 70. Electrical controls shall be mounted in [outdoor
weatherproof enclosure, NEMA 3R] [indoor enclosure, NEMA 1 OR NEMA 12].
Enclosure shall be divided into compartments. Compartment for time clock
and timers shall be separate and isolated from that housing other
electrical components, except that lighting circuit breaker may be included
therein. Electrical controls shall be wired so that the various items of
plant equipment can be operated either manually and/or automatically to
achieve the sequence of operation specified hereinafter. All electrical
control system components shall be completely wired and mounted in the
enclosure at the manufacturer's plant and tested prior to shipment from the
factory. The electric service available is [_____] volt, [_____] phase,
[_____] Hertz, [_____] wire. All push buttons, selector switches, and
indicating lights shall be installed on the outside of the door(s),
properly identified with laminated phenolic name plates. All components on
outside of enclosure and on internal panels shall be identified by engraved
laminated phenolic legend plates.
2.13.2
Sequence of Operation
The electrical control system and its components shall be designed and
interconnected as to perform the following automatic functions:
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NOTE: Delete reference to comminutor when not
required for plant. For plants of 1.09 L/s 25,000
GPD capacity and below, the comminutor and bar
screen unit may be omitted, and in lieu thereof, a
screening basket provided in the aeration tank. For
installations in which all sewage has passed through
a comminutor and bar screen upstream of the plant, a
comminutor and bar screen unit need not be provided
as a part of the plant equipment.
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a.
The 7-day program timer shall automatically start and stop the
blowers [comminutor,] and froth control system pump. A percentage
timer shall automatically start and stop blower motors.
b.
If operating lead blower should stop, standby blower, acting in
response to setting of failure transfer timer, shall automatically
start and stay in operation until such time as lead blower returns
to service. Range of failure transfer timer shall be such as to
prevent the transfer to the standby system from such causes as
momentary interruptions of power, loss of power and similar
malfunctions. A selector switch shall be provided to allow manual
change in the lead-standby system. Pressure switches in the motor
control circuit shall be arranged to cause the system failure
transfer circuit to operate when there is a lack of or loss of
pressure due to belt slippage or breakage, or air loss, until such
time as the fault is corrected. Horn and warning light alarm
circuits shall be energized to indicate that the standby system
SECTION 11375N
Page 70
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