Emerson iPro.Genius, Инструкция по установке и эксплуатации

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Discharge Air Controller (DAC) Manual Software Overview • 23
7.7. Outside Air Control
The outside air damper can be used for several
strategies. They are:
• Economization
• Indoor Air Quality (CO2 Control)
• Make-up Air Control
When the outside air damper does not have any
functions calling for it to be open, the modulating
damper will move to its minimum position and the
two-position damper will close. During occupancy,
the minimum position will be specified by a user
setpoint. During unoccupied, the modulating damper
will fully close to 0%.
7.7.1. Indoor Air Quality
When a CO2 sensor input is present on the DAC
or a CO2 value is received from the E2, the outside air
damper may be used to bring fresh air into the
building to reduce CO2 levels. The CO2 sensor’s
value is compared to the DAC’s CO2 setpoint. If the
reading exceeds the setpoint:
• The damper will OPEN and remain open until the
CO2 value drops below the setpoint (for two-
position dampers).
• The damper will open and modulate its position
based on a PID comparison of the CO2 sensor
reading and the CO2 setpoint (for variable-position
dampers). The damper will open to a user-specified
maximum position.
7.7.2. Make-up Air Control
When an exhaust fan input is present on the DAC
or an exhaust fan active signal is received from the
E2, the controller will activate make-up air control.
When make-up air is becomes active, the modulating
damper will open to the make-up air minimum
damper position setpoint if it is currently less than that
position. If the current modulating damper position is
already greater than or equal to the make-up air
minimum position setpoint, no adjustment to the
damper position will occur.
For the two-position damper, when make-up air
control is active, the damper will be set open. When
make-up air control is inactive, the damper will close.
7.7.3. Economizer Control
Economizer dampers on rooftop HVAC units are
used to bring outside air into the building for use in
cooling. The DAC supports control of two-position
outside air dampers as well as variable-position
(analog) dampers.
The DAC controls economization by first
determining whether the outside air conditions are
favorable for bringing in outside air (see Section
7.7.3.3., Economization Enabling Strategy ). If the air
is not favorable for economization, the DAC will
close the dampers. If the air is favorable for
economization, the DAC will use the dampers like a
preliminary stage of cooling, opening them first when
cooling is first called for, and then activating more
cool stages only if necessary to maintain the setpoint.
7.7.3.1. Operation of Two-Position
Dampers During Economization
Two-position dampers are set to the OPEN
position when economization is enabled and the space
temperature is above the space economization
setpoint. The damper will remain OPEN until cooling
is not required, or until the DAC determines the
outside air is not favorable for economization, at
which time the dampers will be set to the CLOSED
position.
7.7.3.2. Operation of Variable-Position
Dampers During Economization
When economization is enabled and the space
temperature is above the space economization
setpoint, the DAC controls the position of the damper
using a PID algorithm, using a mixed air temperature
sensor (mounted where the sensor may measure the
mixture of outside air and return air) and a mixed air
temp setpoint.
The DAC opens and closes the damper
incrementally to attempt to maintain the mixed air
temp setpoint. The DAC will close the damper when
the mixed air is below the setpoint to keep cooler air
from entering, and open the damper when the mixed
air is above setpoint and requires cooler air from
outside.
If the space temperature becomes too cold, or the
DAC determines outside air conditions are not
favorable for economization, the DAC will close the
damper to a user-defined minimum damper position.