230
JOHNSON CONTROLS
5276178-JIM-C-0118
Service
CO
2
Sensor
Two CO
2
sensors are used in conjunction with the
“DEMAND VENTILATION”
option. In
“DEMAND
VENTILATION”
the Unit Control monitors the CO
2
level of the outdoor air and the CO
2
level in the
conditioned space and varies the amount of ventilation
air based on the relationship between these two values.
Table 88 gives the VDC output for a given CO
2
level.
TABLE 98 - CO
2
SENSOR OUTPUT
PPM CO
2
OUTPUT
VOLTAGE
VDC
PPM CO
2
OUTPUT
VOLTAGE
VDC
80
0.20
1120
2.80
160
0.40
1200
3.00
240
0.60
1280
3.20
320
0.80
1360
3.40
400
1.00
1440
3.60
480
1.20
1520
3.80
560
1.40
1600
4.00
640
1.60
1680
4.20
720
1.80
1760
4.40
800
2.00
1840
4.60
880
2.20
1920
4.80
960
2.40
2000
5.00
1040
2.60
Furnace Status Input
The Unit Controller monitors the operation of the Staged
Gas Heat sections and displays the status through the
STATUS screen of the User Interface. The operation
of each of the gas heat sections is monitored by a
multiplexer installed behind the User Interface panel.
When a gas heat section is energized, it sends a 24V
signal to the multiplexer. The multiplexer takes the
five “ON”/”OFF” inputs and converts them into a 0 to
5VDC signal that is sent to the Unit Controller. The
Unit Controller then decodes this analog input and
displays the furnace section status. Table 89 shows the
relationship between the DC voltage and the furnace
operation status.
TABLE 99 - FURNACE STATUS INPUT STAGED GAS HEAT
MIN VDC
MAX VDC
FURNACE 1 STATUS FURNACE 2 STATUS FURNACE 3 STATUS
0.086
0.166
OFF
OFF
OFF
0.224
0.313
ON
OFF
OFF
0.361
0.461
OFF
ON
OFF
0.499
0.609
ON
ON
OFF
0.637
0.756
OFF
OFF
ON
0.774
0.904
ON
OFF
ON
0.912
1.051
OFF
ON
ON
1.050
1.199
ON
ON
ON
Summary of Contents for 40 25 TON
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