How do I test a thermostat


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Old 02-11-13, 10:52 AM
J
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How do I test a thermostat

I have a State Select electric water heater (model P65220RT2) that has quit heating water. I have replaced both upper and lower heating elements. They both showed some conductivity, but were appeared grey and very rough. I also checked the breaker and it is on with no red showing. It is still not heating. Could both thermostats have gone out? The unit is 12 years old. How can I test the thermostats? Is there some other problem to be considered?
 
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Old 02-11-13, 11:07 AM
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Duel element residential water heater
Both elements do not heat at the same time.
Starting with a tank of cold water, the upper element will heat the water
in the top half of the tank. When the upper thermostat is satisfied the
upper element will shut down and the lower element will begain heating.
This following test will not work if the water temperature is extremely
hot. If this is the case you may have a grounded element.
Visit water heater element testing for more information on grounded
elements.


Water heater elements are easy to check. I recommend that you check
the elements before testing water heater thermostat.


Test water heater thermostat (upper)
Turn the water heater power off.
Remove both access panels, insulation
and plastic safety covers.
Check to ensure that the reset
button has not tripped.
Use a small screwdriver to set the
upper (top) thermostat temperature
to the highest setting (see pic).

Set the lower thermostat
temperature to the lowest
setting.


Turn the water heater power on.
Check the two wires above the reset
button to be sure their is voltage coming
into the water heater (see pic).
This water heater is 240 volts.
Voltage at the elements on this
water heater should be 240 volts.

Place the multimeter probes on the
upper element contact screws (see pic).
If you do not have power at the element
the thermostat needs replacing
If you do have power its time to
check the lower thermostat.


Test water heater thermostat (lower)

Set the upper thermostat temperature
to the lowest setting.
You should hear the thermostat
click off as you turn the dial.
If you don't hear it, give the water
time to heat up and then continue.


Set the lower thermostat temperature
to the highest setting


Check the lower element for
voltage.
If you have power at the element
allow the water to warm a bit.
Lower the temperature on the
thermostat. You should hear it
click off. The thermostat is good.
If you do not have power at
the element go to the next step.

Test the lower thermostat for
power.
Place one multimeter probe on
the top contact screw and the
other probe on the water tank
(see pic).It should read 120 volts.
If you do not get a reading
replace the upper thermostat.
It is not sending power to the
lower thermostat.
If you have power go to the next step.

Place one meter probe on
the lower contact screw and
one probe on the water tank.
You should have 120 volts, if not,
replace the lower thermostat.








Source: Hot Water Heater Thermostat - Test Water Heater Thermostat
 
  #3  
Old 02-11-13, 02:34 PM
J
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Thanks for the information. I found out the red high temperature switch had tripped. When I pushed the reset button in, the heater began heating. I will keep the information you provided for future reference. Thanks again for your help.
 
 

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