The ACO2 sensors/controllers for duct mounting measure the carbon dioxide (CO2) con- centration and the temperature in the return or outside air. They are used in ventilation and air conditioning systems to control the amount of fresh outside air being supplied to the occupants for acceptable indoor air quality and to reduce unnecessary conditioning of outside air during low- occupancy periods.
This Demand Controlled Ventilation (DCV) is a cost effective solution to conserve energy and to ensure that the fresh outside air supplied is no more than is necessary to meet the actual requirements of the occupants at any given time.
The sensors/controllers offer separate
4...20mA outputs for CO2 and temperature and in addition a digital ON/OFF relay output with switching hysteresis for alarm or other purposes.
The UART interface (Modbus) for serial communication allows a PC to be connected in order to perform maintenance checks or reconfigurations during normal operation. If used as a controller, each of these outputs can be configured to provide a more complex ventilation strategy based on a
mixture of CO2 plus temperature measurements and to assign a number of functions, including hierarchy.
For this analog output configuration, the software program STRATEGY is available, which is part of the User Interface Program Software packageACO2 used for re- calibration, change of the measurement range or other service or set-up purposes.
The switching setpoint and differential of the relay output for CO2 limit monitoring or plant/system ON/OFF control can be adjusted within the measurement range. This output can be used also as automatic fire threshold to switch off ventilation, when CO2 levels exceed normal limit of e. g. 2500 ppm in
case of fire.
¡¤ CO2 measurement range 0...3000 ppm corresponding to 0...0.3% CO2. Factory-calibrated 0...2000 ppm
¡¤ Multifunctional unit for temperature and CO2- measurement or control
¡¤ State-of-the-art Non-Dispersion-Infrared (NDIR)
technology to measure carbon dioxide gas
¡¤ Automatic drift correction (ABC-algorithm) based on a long term evaluation provides typical zero drift check maintenance-intervals of up to 5 years
¡¤ Standard output signals 4...20 mA
each for CO2 and temperature measurement or control
¡¤ Programmable mixed controller signal output(s) provides ventilation control strategies to match exactly the application requirements
¡¤ Digital ON/OFF relay output for CO2 limit monitoring
¡¤ Modbus interface for configuration, parameter setting or data exchange with a PC using Windows 95/98
¡¤ User interface program on diskette for service, recalibration and change of measurement ranges
and room temperature alternating
- CO2-concentration (ppm)
- Temperature (¡ãC)
- Analog Output1
- Analog Output2
If used as a controller the actual measured values are compared with the programmed setpoints. Depending on the deviation the control output values are calculated and converted into two separate 0(2)...10Vdc or 0(4)...20mA outputs which can drive directly final control devices. The proportional band settings control the output spans.
In this application the AQS-USP22 software package can be used to configure the available two analog outputs for temperature and ventilation control, and to assign for each output a number of functions to provide different ventilation control strategies.
For rooms where are the occupants the source of the main air pollution, a CO2 concentration of max. 1200ppm should not be exceeded.