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12
Troubleshooting
Table 12-8: Sensor Fault Diagnostic Help
Indication
Not Installed
Open
Shorted
Outside low range
Outside high range
Not reliable
Table 12-9: Supply and Flue Sensor
Temperature vs. Resistance,
10kOhm NTC, Beta = 3977K
Temperature
°F
°C
32
0
41
5
50
10
59
15
68
20
77
25
86
30
95
35
104
40
113
45
122
50
131
55
140
60
149
65
158
70
167
75
176
80
185
85
194
90
203
95
212
100
106308-05 - 3/23
(continued)
Sensor has not been selected. For example, in Figure 12-7, the Header Sensor has not been
selected. Refer to Operations Section, Parameter Adjustment for information on how to select
sensors.
Sensor not connected or loose wire. Check sensor wiring.
Sensor terminals connected to each other or sensor has failed.
•
Check sensor wiring.
•
Check sensor resistance. See Tables 12-9 through 12-12 for temperature versus resistance
values.
Sensor input out of range. Sensor is defective or is being subjected to electrical noise.
Sensor is defective or is being subjected to electrical noise.
Ohms of
Resistance
32650
25390
19900
15710
12490
10000
8057
6531
5327
4369
3603
2986
2488
2083
1752
1481
1258
1072
918
789
680
APEX
Installation, Operating, & Service Instructions
Possible Cause
Table 12-10: Return Sensor
Temperature vs. Resistance,
12kOhm NTC, Beta = 3750K
Temperature
°F
32
50
68
77
86
104
122
140
158
176
194
212
230
248
Ohms of
Resistance
°C
0
36100
10
22790
20
14770
25
12000
30
9810
40
6653
50
4610
60
3250
70
2340
80
1710
90
1270
100
950
110
730
120
560
129
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