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Page 22
Thermal Well Testing (cont’d)
Determine the correct resistance values using the Determine the Water Temperature
Inside the Tank procedure on page 23. If the values are correct, replace the gas
control, otherwise replace the thermal well.
Determine Water Temperature Inside Tank
Note: It is important to understand once the resistance for the thermal well is
determined using the Thermal Well Testing Procedure on page 21, water flow through
the water 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. Move the gas control power switch to the “OFF”
position.
Step 2. Draw approximately 4 gallons of water from the drain valve into a
container and discard. Draw an additional gallon and immediately measure the 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 on page 23, determine the 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.
WARNING
Stored water may be HOT when performing the following steps in this procedure. Take
necessary precaution to prevent personal injury.
Determine Tank Temperature
Gas control power
switch
22