Figure 5: Transmitter PCB
Configuring the Output
About this task:
The transmitter is capable of generating either voltage or
current output. To select, refer to Figure 5 and:
1. Connect the common wire to Terminal 0.
2. Connect the other wire to:
- Terminal V (for voltage output)
- Terminal mA (for current output) and
configure the pins marked 0/4mA as follows:
- - 4 to 20 mA: connect the jumper so
that it shorts the pins (default)
- - 0 to 20 mA: disconnect (do not
discard) the jumper
3. If the unit has an optional relay accessory, follow
the procedure described in the
section and then reposition the cover.
Wiring the Relay
Model CD-PR0-00-0 is shipped with a relay module. To wire
the relay, see Figure 6, and attach the relay wires to the
relay PCB's two screw terminals.
Figure 6: Relay PCB
The relay has two setpoint values: the On level and the Off
level. These levels provide hysteresis and desired control
function. The On level must be higher than the Off level.
When CO
2
concentration is increasing; the relay closes at
the On level, and the relay opens when concentration is
reduced to the Off level.
Note:
The default relay setpoints are 1,000 ppm On
and 950 ppm Off. Change these settings by entering
new values using the Relay Setpoint Software ACC CD
S.
Setup and Adjustments
Commissioning
Johnson Controls® Carbon Dioxide (CO
2
) transmitters
come from the factory calibrated for the following:
• output signal (0 to 10 V) proportional to CO
2
concentration (0 to 2,000 parts per million [ppm])
• altitude range of 0 to 1,969 ft (0 to 600 m) above sea
level without compensation
• default relay output trigger point of 1,000 ppm
Altitude Compensation
The sensors are calibrated for an altitude of 984 ft (300
m) above sea level and are intended for applications
within the range of 0 to 1,969 ft (0 to 600 m) without
compensation.
For altitudes above 1,969 ft (600 m) where optimum
accuracy of the CO
2
concentration measurement is
essential, modify the Building Automation System (BAS)
controller’s Analog Input (AI) high range to compensate
for sensor placement at other than the standard
calibration altitude.
Note:
For altitude compensation, only adjust the AI
high range. The AI low range should remain at zero.
To modify the controller’s AI, reset the 2,000 ppm value
using the controller's Compensation Factor (CF) shown in
Figure 7 or Figure 8 as follows:
Corrected Value = CF x 2,000
For example, if the sensor is situated at an altitude of 3,000
ft (914.4 m) above sea level, CF, from either Figure 7 or
Figure 8, is 1.10.
The new value is calculated as follows:
Corrected Value = (1.10)(2,000 ppm) = 2,200 ppm
Figure 7: Altitude Compensation in Feet Above Sea
Level
CD-Pxx-00-0 Series Duct Mount CO
2
Transmitter Installation Guide
3