Service Manual
3Troubleshooting
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.
Table 3B - Inlet/Outlet System Sensor Resistance vs. Temperature
Temperature | Resistance |
| Temperature | Resistance |
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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 |
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Table 3C - Flue Temperature Sensor Resistance vs. Temperature |
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Temperature | Resistance |
| Temperature | Resistance |
|
|
|
|
|
68 | 14,773 |
| 176 | 1,707 |
|
|
|
|
|
86 | 9,804 |
| 194 | 1,266 |
|
|
|
|
|
104 | 6,652 |
| 212 | 952 |
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|
|
|
|
122 | 4,607 |
| 230 | 726 |
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|
|
140 | 3,252 |
| 248 | 560 |
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158 | 2,337 |
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Table 3D - Outdoor Air Sensor Resistance vs. Temperature |
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Temperature | Resistance |
| Temperature | Resistance |
|
|
|
|
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490,813 |
| 20 | 46,218 | |
|
|
|
|
|
336,606 |
| 30 | 34,558 | |
|
|
|
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|
234,196 |
| 40 | 26,099 | |
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|
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|
165,180 |
| 50 | 19,900 | |
|
|
|
|
|
10 | 118,018 |
| 60 | 15,311 |
|
|
|
|
|
0 | 85,362 |
| 70 | 11,883 |
|
|
|
|
|
10 | 62,465 |
| 80 | 9,299 |
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