acceptable
d.
Enclosure mounted devices shall be properly supported, front and
rear and shall occupy the upper portion of the enclosure front.
e.
Enclosure wiring shall comply with acceptable standard panel
practice.
f.
The 120 volt, 60 Hz circuit wiring shall be number 16 AWG minimum,
THWN 600 volt insulation, color coded. Signal circuits, less than
50 volts, shall be number 18 AWG minimum or number 20 AWG in
multi-conductor cable.
g.
Devices requiring power shall be wired so that when wires are
removed from one device, power will not be interrupted to other
devices. Enclosure-mounted devices shall be wired to numbered lug
and screw terminals so that field wiring can easily be terminated
in the panel.
h.
Signal common and power common buses shall be supplied.
Signal
common shall be connected to earth ground at one point.
2.5.6
Controllers
**************************************************************************
NOTE: Single loop controllers are specified.
Consider programmable logic controllers (PLCs) as an
option.
**************************************************************************
a.
Controller shall be microprocessor-based and shall be of single
loop design. Controller shall be flush-mounted in control cabinet
and shall have splash-proof mylar faces. Operator pushbuttons
shall be of the membrane type and have tactile feedback. A 4-1/2
digit numeric display shall be provided on front of controller.
b.
Two bar graphs shall be provided on the front of controller to
give an analog interpretation of process variables, setpoints or
deviation. These shall be of the 100 segment LED type. A
dedicated 20 segment LED bar graph shall be provided for the
controller main output.
c.
Each controller that drives a final control device (damper, valve
or other) shall be provided with a hard manual backup station to
ensure operator control in the event of a memory failure or
service requirement.
d.
Controller output logic shall include proportional, plus integral,
plus derivative (PID) modes.
e.
Multiple loops on single controller are not acceptable. During
integral hard manual backup mode, operator shall have control of
output via up-down pushbutton and shall have output indication.
f.
Should the controller or memory fail, controller shall deenergize
a dead-man relay and alert operator to use backup station.
g.
Backup station may be separate station or may be integral to main
controller. If Integral, backup circuitry must function when
SECTION 15561A
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