Checking Temperature Sensors - Lochinvar Shield SNR200-100 Installation And Service Manual

13
Troubleshooting

Checking temperature sensors

The water heater temperature sensors (inlet water, outlet water, tank water, and flue) 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 13B - Inlet/Outlet Tank Sensor Resistance vs. Temperature
Temperature °F
50
68
86
104
122
140
Table 13C - Flue Temperature Sensor Resistance vs. Temperature
Temperature °F
68
86
104
122
140
158
60
Resistance Ω
18,780
12,263
8,194
5,592
3,893
2,760
Resistance Ω
14,773
9,804
6,652
4,607
3,252
2,337
Installation & Service Manual
TM
Temperature °F
158
176
194
212
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Temperature °F
176
194
212
230
248
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Resistance Ω
1,990
1,458
1,084
817
--
--
Resistance Ω
1,707
1,266
952
726
560
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