Indoor Air Quality (IAQ)
Proper ventilation control
is perhaps the single most important contributor to the quality
of air in enclosed spaces. Some common approaches to ventilation
control lead to excessive outdoor air intake and result in a massive
energy waste
Digital Air Volume (DAV) Systems
can easily be configured to accommodate a more dynamic ventilation
method, one which automatically adapts to the movement of occupants
within a building. This ventilation method, known as Zoned CO2
Control, offers a viable strategy for achieving the goal of indoor
air quality, and is one of several approaches referenced in ASHRAE
std. 62-1989.
Zoned CO2
Control - Carrier
offers Zoned CO2 Control as an integrated system which
includes the Terminal Control Unit, a microprocessor-based controller
for air terminals, and Carrier air handlers with integrated electronic
controls (via the PIC or Comfort Controller). Zoned air quality
control is provided by modulating the terminal airflow in response
to both temperature and indoor air CO2 levels in conjunction
with the Air handling equipment's outdoor air damper.
Carrier's Zoned CO2
Control system can be configured to provide the minimum, maximum
and calculated average CO2 sensor values for each zone
location. The air handler control then uses the average or maximum
value to adjust outside air intake.
As zone CO2 levels
increase, the terminal airflow to the space is increased until
the zone temperature is adversely affected. At that point, the
air handler increases its outside air intake. Over time, the system
automatically adjusts to the point at which the terminal airflow
maintains the zone temperature, and the air handler's mixed-air
damper maintains the zone CO2 setpoint. A return duct-mounted
VOC or CO2 sensor may be added to insure the air quality.
How It Works - A unique feature of Carrier's Zoned CO2 Control system is its ability to respond to the zone with the highest CO2 value. Particularly in zones with large, variable occupancy densities, Zoned CO2 Control effectively enhances indoor environmental quality while reducing operating costs. Through the use of Relative Humidity (RH) sensors, a similar type of zoned RH control system can be configured.