38
Servicing should only be performed by a Quali
fi
ed Service Technician
CHECKING TEMPERATURE SENSORS
The water heater temperature sensors (inlet water, outlet water, system water, and
fl
ue) 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.
It is important to note that the
fl
ue and outlet water sensors have two temperature sensing devices in one
housing. These devices are designated as S1a/S1b, outlet sensor and S3a/S3b,
fl
ue sensor. Please reference
the wiring diagram in the XP Water Heater Instruction Manual for correct terminal location.
Table 11. Inlet System Sensor Resistance vs. Temperature
TEMPERATURE °F
RESISTANCE
TEMPERATURE °F
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 11.1 - Outlet Water Sensor Resistance vs. Temperature
S1A
(WIRE COLOR - R/BK AND Y)
S1B
(WIRE COLOR - G 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
Table 11.2 - Flue Sensor Resistance vs. Temperature
S3A
(WIRE COLOR - W/B AND Y)
S3B
(WIRE COLOR - PR AND Y)
TEMPERATURE RESISTANCE
TEMPERATURE RESISTANCE TEMPERATURE RESISTANCE
TEMPERATURE
RESISTANCE
50
40,030
158
3,478
50
258,500
158
16,870
68
25,030
176
2,492
68
125,500
176
12,000
86
16,090
194
1,816
86
80,220
194
8,674
104
10,610
212
1,344
104
52,590
212
6,369
122
7,166
122
35,270
140
4,943
140
24,160
