Lochinvar SMART SYSTEM 502 - 2072 - Manual (Page 33)

3
Troubleshooting
(continued)
33
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 appliance temperature sensors (inlet water, outlet water, system water, tank 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/Tank Sensor Resistance vs. Temperature
Table 3C Outdoor Air Sensor Resistance vs. Temperature
Copper-fin II/IIE Boiler, Water Heater and Pool Service Manual
S1a
(Wire Color - W and Y)
S1b
(Wire Color - W/Y 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