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3 Troubleshooting (continued)
45
Table 3B - Inlet/Outlet System 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 -- --
Table 3C - Flue Temperature Sensor Resistance vs. Temperature
Temperature Resistance Temperature Resistance
68 14,773 176 1,707
86 9,804 194 1,266
104 6,652 212 952
122 4,607 230 726
140 3,252 248 560
158 2,337 -- --
Table 3D - Outdoor Air Sensor Resistance vs. Temperature
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
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.
Service Manual