shall include the following:
a.
Proportional band:
2.5 to 33 percent of input device span.
b.
Authority:
minimum of 33 to 200 percent.
c.
Inputs: thermistor, resistance, transmitter, or output of other
electronic controllers.
d.
Outputs: within the range of minus 5 to 20 Vdc or a 4 to 20 mA dc
current loop.
e.
Remote setpoint adjustment (SPA):
plus or minus 10 percent of
input device span.
2.13.4
Unitary Control Systems
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NOTE: Energy-efficient temperature control systems
should be used for small systems as well as large
systems. Systems that otherwise are not cost
effective may use programmable controllers that are
commercially available for HVAC applications. These
are chiefly staging type controllers but some do
incorporate modulating outdoor air damper control.
Controllers are available to control cooling in two
steps with either two or four heating steps, and in
three cooling steps with three heating steps.
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Unitary control systems shall be energy-efficient, micro-processor-based
temperature controllers and associated devices that do not require
Contractor-generated software. Provide control systems with [integral]
[or] [remote] sensor as indicated. Controllers shall operate heating,
cooling, and ventilating modes with independent occupied and unoccupied
settings for each of 7 consecutive days. Cooling shall be controlled in
[two] [three] steps and heating shall be controlled in [two] [three] [four]
steps with modulating control provided for the ventilation mode. Provide
temperature changeover control to limit the ventilation mode when outdoor
air temperature is not sufficiently low for "free-cooling." Provision
shall be made for [automatic] [manual] changeover between heating and
cooling modes, providing a one minute minimum time delay between the start
and stop operation of heating and cooling stages upon startup and after
power failure to prevent short cycling and power surges. Provide an
optimum startup program to minimize warm-up or cool-down periods prior to
the occupied mode. Outside air dampers shall be closed during the optimum
startup program unless outside air is beneficial for cool-down in lieu of
mechanical cooling. Fan shall operate continuously during the occupied
mode and shall cycle during the unoccupied mode for heating or cooling.
Provide battery backup to retain programs and maintain clock operation for
48 hours minimum during power outages. Controller shall have a
self-diagnostic program to indicate errors and locking covers to prevent
unauthorized program entries. Provide a convenient means to restore the
occupied mode of operation for a minimum 2-hour period without removing
covers. An indexing switch shall allow operation in a continuous
unoccupied mode during abnormal periods without changing normal programs.
[Servicing tool required to place the unitary control system in use shall
be a hand-held device used to adjust and monitor setpoints, controlled
device positions, input sensor values, and other control system parameters.]
SECTION 15901N
Page 34
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