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2004 – 2014 Reliable Controls
®
Corporation. All rights reserved.
W
IRING
The duplex RJ11 connection port on the rear of the sensor head has been removed to
make room for the CO
2
sensor. There is a standard 6-pole wiring terminal block on the
backplate which must be used for connecting models with the -CO2 option to SMART-
Net
™
daisy-chain wiring.
For more information, please refer to the Wiring Details section earlier in this document.
C
ALIBRATION
The CO
2
sensor is factory calibrated, however, some calibration drift during shipping and
installation is typical. However, there are exceptions that will require the use of a built-in
automatic calibration algorithm. Specifically, when the lowest CO
2
levels in any enclosed
space being monitored does not drop to about 400 PPM.
For applications where the CO
2
sensor is exposed to fresh air CO
2
concentrations of 400
ppm at least once per week, the automatic calibration routine will calibrate the sensor to
specification within about 3 weeks. For applications where the sensor is not exposed to
400 ppm concentrations at least once every two weeks, manual calibration may be carried
out to increase final accuracy. Both automatic and manual calibration methods are
described below.
A
UTOMATIC
Automatic calibration occurs once in the first 24 hours after a power cycle, and then recurs
every two weeks thereafter. The lowest CO
2
value recorded during the cycle is compared
to 400 ppm, then the sensor is calibrated by the difference of the two values.
If unwanted air flow is entering the sensor from the wall cavity, the grommet may be sealed
with silicone sealant at the wire penetration point. This will prevent airflow within the wall
cavity from disturbing the reading. Silicone sealant outgassing will NOT damage the CO
2
sensor.
