16
G
Installation and Commissioning
ATTENTION !
The minimum CO2
concentration of outdoor air amounts to approx. 350 ppm in leafy, hardly industrialised areas. Gas inter-exchange in the sensor
element happens by diffusion.
Depending on the changes to the concentration and the flow velocity of the air surrounding the sensor, the reaction of
the device to the change of concentration may take place with a delay. It is essential to choose an installation location for the device
in which the air
stream flows around the sensor. Otherwise the gas exchange may be considerably delayed or prevented.
General information on air quality
The service life of the sensor depends on its functional principle and the type and concentration of pollutant gas burden. The sensitive layer of the
sensor element reacts with all volatile organic compounds and is therefore modified in its electrical properties. This procedure leads to an offset of
the characteristic line. When measuring the air quality, the general condition of the air quality is recorded. Whether the air quality is “good” or “bad”
depends on the individual interpretation of each individual. Different pollution burdens and concentrations influence the air quality signal (0 - 10 V) in
different ways. Examples are cigarette smoke, deodorant sprays, cleaning agents and various adhesive materials for floor and wall coverings, as well
as dyes. Increased levels of solvents, nicotine, hydrocarbons, aerosol propellants, etc. intensify the wear/ageing of the sensor element. Especially at
high pollutant gas burdens, even when the devices are idle (transport and storage) the zero point is adjusted. This must be corrected on-site
depending on the specific conditions or basic burdens. Air quality measuring instruments from various manufacturers cannot be compared directly
with each other because of the different functional principles, the pre-set basic burden (zero point) and the permitted burden (amplification/sensitivity).
The devices are set or calibrated according to the specifications of the sensor manufacturer. Here, a zero point and end value, and therefore a
maximum load, are established. In special circumstances, there is an overrun of the measuring range or an excessively high basic burden on the
devices (out gassing carpets, wall paint, etc.) In order to enable a measurement or distinction of different air qualities, the devices must be configured
by the client in accordance with the on-site conditions which do not correspond to the function domain and thus the factory calibration. Here, it
should be noted that the factory calibration will be lost and technical data compliance can no longer be guaranteed.
Commissioning
After the device is switched on, a self-test and temperature equalisation are performed. Depending on the ambient conditions, this process takes
30-50 minutes (
as an option, manual calibration
can now be performed). If commissioning with
automatic calibration
, proceed as follows:
1.
Open all windows or set the air conditioning system to use outdoor air
2.
Switch on the device and move away from the device. If possible, all persons should leave the room.
3.
The device is ready to use after 50 minutes.
Automatic calibration of the CO2 measurement
The regular exchange of fresh air is all that is required for the self-calibration technology in the sensor (CO2 concentrations: 350-500 ppm). The
device detects this condition and performs the calibration automatically. It is sufficient to open the windows or set the air conditioning system to use
outdoor air at regular intervals and to stop all CO2-producing processes that influence the ambient air. Proceed as follows:
Open all windows fully or set the air conditioning system to use outdoor air 1x weekly for 15-20 minutes.
If possible, all persons should leave the room during this time.
Regular ventilation of the rooms and flushing of the duct with fresh air will increase the measuring accuracy of the sensor.
Automatic calibration
is deactivated by default in the as-delivered condition and, if required, must be activated using the Modbus.
Manual calibration of CO2 measurement
Manual calibration can be carried out independently of automatic calibration. Sufficient fresh air must be
provided before and during the calibration procedure (CO2 concentration: 350-500 ppm). Also make sure that
no CO2-producing processes influence the ambient air. Proceed as follows to perform manual calibration:
1.
Preparation: Remove the housing cover and open all windows or set the air conditioning system to use
outdoor air.
2.
Press and hold the “
ZERO CO2
” button until the flashing LED row changes to a steady light after 5
seconds. Devices with a display indicate “
AUTO 0
” and change the countdown from 5 to 600.
The calibration process has started. Keep the windows open or the air conditioning system set to use
outdoor air.
3.
If possible, all persons should now leave the room.
4.
After 10 minutes, the calibration is complete (status LED has gone out, the countdown is complete) and
the device should indicate or transmit a CO2 concentration of between 350-500 ppm.
