Bradford White MI30T Service Manual page 23

The Bradford White
DEFENDER
Safety System
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 temperature sensor is determined from the
previous page, water flow through the water heater should not occur. Prior to drawing water from drain
valve, turn off the cold water supply to the water heater. This will prevent cold water flow into the tank
affecting the resistance value of the temperature sensor.
Step 1. Set the Gas Control knob to the "OFF" position.
Step 2. Turn off inlet water supply to water heater.
Step 3. Draw approximately 4 gallons of water from drain valve into a container, or suitable drain, and discard.
Draw an additional gallon and immediately measure water temperature using an accurate thermometer.
It may be necessary to open a hot water faucet to allow water heater to drain.
Step 4. Using the chart below, determine correct resistance value for the water temperature from step 3.
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
decreases.
°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
190 982 965
200 828 814
®
WARNING
Sensor Resistance at Various Temperatures
In Degrees F
1 2 3
24712 24045 23399
18876 18383 17905
14548 14180 13823
11308 11032 10763
8862 8653 8449
7000 6839 6683
5570 5446 5326
4464 4368 4274
3602 3527 3453
2925 2866 2808
2391 2344 2298
1966 1928 1891
1625 1595 1566
1351 1327 1303
1129 1110 1090
949 933
801 788
SERVICE PROCEDURE RG-VI
Testing, Disassembly & Replacement (Honeywell)
4 5 6
22771 22163
17440 16990
13477 13140
10502 10248
8250 8057
6531 6383
5208 5094
4183 4094
3382 3312
2752 2697
2253 2209
1856 1820
1537 1509
1280 1257
1071 1953
917 901 886
775 762 749
23
Gas Control
7 8 9
21573 21000 20445
16553 16128 15715
12812 12494 12185
10000 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
23 23