TM

Installation & 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

Resistance Ω

Temperature °F

Resistance Ω

 

 

 

 

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 13C - Flue Temperature Sensor Resistance vs. Temperature

 

 

 

 

 

Temperature °F

Resistance Ω

Temperature °F

Resistance Ω

 

 

 

 

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

--

--

 

 

 

 

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Lochinvar SNA500-125, SNR200-100, SNA285-125, SNR150-100, SNA400-125 Checking temperature sensors, Temperature F Resistance Ω

SNA400-125, SNR150-100, SNA285-125, SNR200-100, SNA500-125 specifications

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