76
13
Troubleshooting
Table 13-2A - Inlet Water/System/DHW Sensor
Resistance vs. Temperature
Table 13-2B - Outdoor Air Sensor Resistance vs.
Temperature
Checking temperature sensors
The boiler temperature sensors (inlet water, outlet water, system water, flue, and outdoor air) are all resistance type devices. The
following tables show the correct values for the sensors at various temperatures. Use an ohmmeter to read the resistance of the
sensor at a known temperature. If the resistance of the sensor does not closely match its corresponding table, replace the sensor
It is important to note that the flue and outlet water sensors have two temperature sensing devices in one housing. These devices
are designated as S1a/S1b, outlet sensor and S3a/S3b, flue sensor. Please reference the wiring diagram in Section 14 of this
manual for correct terminal location.
Table 13-2C - Outlet Water Sensor Resistance vs. Temperature
Table 13-2D - Flue Sensor Resistance vs. Temperature
Temperature Resistance Temperature Resistance
50
18,780
158
1,990
68
12,263
176
1,458
86
8,194
194
1,084
104
5,592
212
817
122
3,893
140
2,760
Temperature Resistance Temperature Resistance
-50
490,813
20
46,218
-40
336,606
30
34,558
-30
234,196
40
26,099
-20
165,180
50
19,900
10
118,018
60
15,311
0
85,362
70
11,883
10
62,465
80
9,299
S1a
(Wire Color - R/BK and Y)
S1b
(Wire Color - G and Y)
Temperature Resistance Temperature Resistance Temperature Resistance Temperature Resistance
50
19,553
158
2,004
50
40,030
158
3,478
68
12,690
176
1,464
68
25,030
176
2,492
86
8,406
194
1,084
86
16,090
194
1,816
104
5,715
212
816
104
10,610
212
1,344
122
3,958
122
7,166
140
2,786
140
4,943
S3a
(Wire Color - W/B and Y)
S3b
(Wire Color - PR and Y)
Temperature Resistance Temperature Resistance Temperature Resistance Temperature Resistance
50
40,030
158
3,478
50
258,500
158
16,870
68
25,030
176
2,492
68
125,500
176
12,000
86
16,090
194
1,816
86
80,220
194
8,674
104
10,610
212
1,344
104
52,590
212
6,369
122
7,166
122
35,270
140
4,943
140
24,160
Installation & Service Manual
F I R E T U B E C O M B I
™
