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.

CO2 Monitor

When a CO2 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 CO2 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