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68-0173—3 38
dehumidification requirement is still not met, cooling starts
again. This switching continues until the dehumidification and
cooling setpoints are met. This feature assures that the
occupants do not experience excessive temperature drop due
to the need for dehumidification.
CO
2
Monitor
When a CO
2
monitor is configured and installed, the Comfort
Center™ programl turns on ventilation (if configured for
ventilation), or
system fan (if configured for no ventilation), in
response to a high CO
2
monitor reading.
C7089A Outdoor Temperature Sensor
The outdoor temperature sensor is necessary for the Frost
control feature to be activated. The Comfort Center™ control
system takes the outdoor temperature reading and calculates
the dewpoint to help prevent humidity from accumulating on
the windows. With the C7089A installed and configured, the
user can read the outdoor temperature by pressing the
CHECK key. See Fig. 39 for the resistance vs. temperature
characteristics for the C7089A Outdoor Temperature Sensor.
When a C7089A Outdoor Temperature Sensor is configured
and installed and the PC8900A is configured for humidity
control in the heating mode, the frost control feature is
enabled.
Fig. 39. C7089A Outdoor Temperature Sensor and C7100A Discharge Temperature Sensor
resistance vs. temperature performance characteristics.
C7100A Discharge Air Temperature Sensor
The C7100A Discharge Air Temperature Sensor mounts on
the duct wall or plenum surface with integral mounting flange
or in a 2 x 4 in. junction box. The C7100A senses the air tem-
perature in the discharge and if the temperature is not
acceptable for the heating or cooling setting, the Comfort
Center™ control system lights the check LED and presents a
Check message. See Fig. 39 for the resistance vs. tempera-
ture characteristics for the C7100A Discharge Air Temperature
Sensor.
The discharge air temperature is displayed on the PC8900A
when the Check key is pressed. If the PC8900A is configured
for a discharge air temperature but the discharge air tempera-
ture is not displayed, then a power outage has cleared the
discharge air temperature reading from the Check feature. To
re-establish the discharge air temperature, enter the installer
OHM RESISTANCE
F
( C )
M6358
RESISTANCE INCREASES 4.84 OHMS PER 1 F CHANGE OR 8.7 OHMS PER 1 C CHANGE.
1
1
3800
3900
3700
3300
3400
3500
3600
3200
TEMPERATURE
-40
(-40)
-20
(-29)
0
(-18)
20
(-7)
40
(5)
60
(16)
80
(27)
3100
2900
3000
2800
100
(38)
120
(49)
140
(60)
160
(79)
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
145
150
-40.0
-37.2
-34.4
-31.7
-28.9
-26.1
-23.3
-20.6
-17.8
-15.0
-12.2
-9.4
-6.7
-3.9
-1.1
1.7
4.4
7.2
10.0
12.8
15.6
18.3
21.1
23.9
26.7
29.4
32.2
35.0
37.8
40.6
43.3
46.1
48.9
51.7
54.4
57.2
60.0
62.8
65.6
2929 to 2905
2953 to 2929
2978 to 2953
3002 to 2978
3026 to 3002
3050 to 3026
3074 to 3050
3099 to 3074
3123 to 3099
3147 to 3123
3171 to 3147
3195 to 3171
3220 to 3195
3244 to 3220
3268 to 3244
3292 to 3268
3316 to 3292
3341 to 3316
3365 to 3341
3389 to 3365
3413 to 3389
3437 to 3413
3462 to 3437
3486 to 3462
3510 to 3486
3534 to 3510
3558 to 3534
3583 to 3558
3607 to 3582
3631 to 3607
3655 to 3631
3679 to 3655
3703 to 3679
3728 to 3703
3752 to 3728
3776 to 3752
3800 to 3776
3824 to 3800
3849 to 3824
OUTDOOR TEMPERATURE
OHMS OF
RESISTANCE
F
C