Determine Water Temperature Inside Tank - Bradford White M1TW40S Series Service Manual

Stored water may be HOT when performing the following steps in this procedure.
Take necessary precaution to prevent personal injury.

Determine Water Temperature Inside Tank

Note: It is important to understand once the resistance for the thermal well is determined from page 24, water flow
through the heater should not occur. Prior to performing the steps below, turn off the cold water supply to the
water heater. This will prevent cold water flow into the tank affecting the resistance value of thermal well.
Step 1. Position gas control power switch to "OFF" position.
Step 2. Draw approximately 1 quart of water from drain valve into container and immediately measure water
temperature using an accurate thermometer. It may be necessary to open a hot water faucet to allow
heater to drain.
Step 3. Using the chart below, determine correct resistance value for the water temperature from step 2.
Example: If temperature of water is 84°F, then the resistance through the sensor would be
8449 (see shaded area). NOTE: Sensor resistance increases as the temperature
falls.
°F 0
40 26109 25400
50 19906 19383
60 15314 14925
70 11884 11592
80 9299 9078
90 7333 7165
100 5827 5697
110 4663 4562
120 3758 3679
130 3048 2986
140 2488 2439
150 2043 2004
160 1688 1656
170 1402 1376
180 1170 1150
190 982
200 828
WARNING
Sensor Resistance at Various Temperatures
In Degrees F
1 2 3
24712 24045
18876 18383
14548 14180
11308 11032
8862 8653
7000 6839
5570 5446
4464 4368
3602 3527
2925 2866
2391 2344
1966 1928
1625 1595
1351 1327
1129 1110
965 949 933
814 801 788
TTW SERVICE PROCEDURE VI
Gas Control/Thermal Well Testing and
4 5 6
23399 22771 22163
17905 17440 16990
13823 13477 13140
10763 10502 10248
8449 8250 8057
6683 6531 6383
5326 5208 5094
4274 4183 4094
3453 3382 3312
2808 2752 2697
2298 2253 2209
1891 1856 1820
1566 1537 1509
1303 1280 1257
1090 1071 1053
917 901 886
775 762 749
Replacement
7 8 9
21573 21000 20445
16553 16128 15715
12812 12494 12185
1000 9760 9526
7869 7685 7507
6238 6098 5961
4982 4873 4767
4006 3922 3839
3244 3177 3112
2643 2590 2538
2166 2124 2083
1786 1753 1720
1481 1454 1427
1235 1213 1191
1035 1017 999
871 857 842
737 725 713
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