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Carbon Dioxide Sensor
Product Information Sheet
210-2000
Wiring
The mounting plate has two sets of three-terminal
connectors. The connector on the left side of the
mounting plate is where sensor power and the signal-
to-I/O-board connection is made. The connector on
the right side is where connection to the on-board
relay is made.
Power Wiring
The CO
2
sensor requires 24VAC power from a non-
center-tapped transformer. The sensor draws a
maximum of 3VA power. CPC recommends P/N 640-
0039, 10VA, 110VAC non-center-tapped Class 2
transformer.
Wire the transformer secondary to the connector on
the left side of the mounting plate, as shown in Figure
2.
Analog Output Wiring
The middle terminal of the connector on the left side
of the mounting plate is the analog output that
communicates the current CO
2
concentration level to
the site controller. This connector is typically
connected to a point on an I/O board, such as a 16AI,
16AIe, or 8DO. Wire the middle (SIGNAL) terminal on
the CO
2
sensor to the even numbered terminal of the
I/O board point. Wire the COMMON terminal on the
CO
2
sensor to the odd numbered terminal of the I/O
board point. See Figure 2.
Relay Wiring
The CO
2
sensor has an on-board relay that changes
state to indicate a CO
2
level higher that a
programmed set point. This relay can be used as a
digital input on an input board point, or it can be used
to directly activate or deactivate an alarm
annunciator or a device that controls ventilation.
The connector on the right side of the mounting plate
is a Form C connector for the CO
2
sensor relay.
Connect the input board point or device to the
middle (COMMON) terminal of this connector, and
either the N.C. or N.O. terminal, depending on
whether you want the relay to be OPEN or CLOSED
when the CO
2
concentration is below the set point.
See Figure 2.
Reassembly After Wiring
When you are finished wiring power and I/O to the
connectors on the mounting plate, reconnect the
circuit board to the mounting plate. Push the top end
of the circuit board into the mounting plate so the
two hooked tabs on the circuit board are underneath
the tabs on the mounting plate. Then, gently press
down on the bottom part of the circuit board until it
snaps into place. See Figure 3.
If you have trouble pushing the circuit board in, check
to see if the pins on the back of the circuit board are
properly aligned with the power and relay connectors
on the mounting plate. Also verify that there are no
loose wires getting in the way.
Figure 2 - CO
2
Sensor Wiring
41